Tag Archive | "electronics"

Learn electronics with Chris Gammell and “Contextual Electronics”

Electrical engineer Chris Gammell has spent almost a year creating his new online electronics program called “Contextual Electronics“, and we’re excited to share this with our readers. You may have heard of Chris from his regular successful podcast with Dave Jones  – “The Amp Hour“.

Chris has the knowledge and expertise to take electronic ideas from simply that – an idea, right through to production. And by participating in his Contextual Electronics program you can learn the required skills to do this as well. Chris gives us a quick introduction in this video.

Contextual Electronics is a new program aimed at electronics enthusiasts who are ready to take their Arduino (or similar platform) skills to the next level. The first session of the course is an 8 week program that will teach you how to design a large, multi-function Arduino shield using KiCad, the open source CAD software.

It will also show you all of the design decisions that go into making the project. Here are some of the sub-circuits included in the 4-layer PCB design:

  • High level signals measurement using op-amps
  • Power supply output
  • Relay control
  • LED driver circuitry
  • Current source output

The course has a large community component, so you will be grouped with others learning at the same time, regardless of where you’re located in the world. The goal of the course and the community aspect is to make you more confident designing a project so you can go and design your own.

Future sessions of the course will also go over building, troubleshooting and coding for the shield described above. There is also a free short course that you can review to give you an idea of Chris’ methods and what the Contextual Electronics program will be like.

Additional courses will be developed using other popular development boards, including the Raspberry Pi and BeagleBone. For a more in-depth introduction, check out this video.

Frankly the program will help all of you who are ready to take your ideas and projects off the breadboard and into finished products, and with the guidance available with the program and the use of open-source tools you’ll be up and making things you can be proud of showing to friends or even potential employers. For more information about the program, and to sign up – visit the Contextual Electronics program website.

And if you enjoyed this article, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop”.

visit tronixlabs.com

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in chris gammell, contextual, education, electronics, kicad, PCB

Old Kit Review – Talking Electronics Fluorescent Simulator

Introduction

Slowly we’re working through the stock of old kits, and in this article we have the “Fluorescent Lamp” simulator from Talking Electronics. To save repeating myself you can read more about Talking Electronics here and watch interviews of the founder Colin Mitchell here.

So why would you want to simulate a fluoro’ tube anyway? Model railways! When your model world moves from day to night, it’s neat to have street lights and so on “flicker” on just like the real thing. And thus you can create this effect as well. It can drive incandescent lamps up to 12V, and allowing it to be powered easily from most layouts.

The kit was originally described in the Talking Electronics book “Electronics for Model Railways” (volume 1) which was full of useful and interesting electronics to liven up any layout. The book may now out of print however at the time of writing this you can download or view most of the projects from the index column of the Talking Electronics website… or contact Talking Electronics if they have any copies of the book (or kit) to sell.

Assembly

Time was not kind to the kit, to be frank it was surprising to find one at all:

Talking Electronics Fluorescent Simulator kit

(Just a note for any over-enthusiastic readers, Talking Electronics is no longer at the address on the bag shown above). However it was complete and ready for assembly. The PCB has a silk-screen with the required component placement information, polarities and so on – a first for the time:

Talking Electronics Fluorescent Simulator PCB top

Talking Electronics Fluorescent Simulator PCB bottom

The instructions and “how it works” are not included with the kit as you were meant to have the book, however TE have made them available as a separate download (.pdf) The kit included everything required to get started, and there’s an LED which replicates the effect so you can test the board without having to watch the connected bulb (which may be a distance away). Finally an IC socket is included 🙂

Talking Electronics Fluorescent Simulator parts

The actual assembly process was very straight forward, which simply required starting with the low-profile components and working up to the large ones:

Talking Electronics Fluorescent Simulator assembly 1

The only problem with the PCB was the holes – looks like only one drill size had been used (apart from the mounting holes) which made getting that rectifier diode in a little tricky. Otherwise it was smooth sailing.

Talking Electronics Fluorescent Simulator finished 2

Not having a model railway at the moment left me with the simple example of the onboard LED and a small incandescent globe to try with the circuit. You can see the kit working in this video.

John – Why do you publish these “Old Kit Reviews”?

They’re more of  a selfish article, like many electronics enthusiasts I have enjoyed kits for decades – and finding kits from days gone by is a treat. From various feedback some of you are enjoying them, so they will continue for fun and some nostalgia. If you’re not interested, just ignore the posts starting with “Old”!

Conclusion

For a kit from the mid-1980s, this would have solved the problem neatly for model railway enthusiasts. By using two or more of the kits with different capacitor values, many model lights could blink on with seemingly random patterns. However it’s 2014 so you could use a PIC10F200 or ATtiny45 and reduce the board space and increase the blinking potential.

Nevertheless, it was an interesting example of what’s possible with a digital logic IC. Full-sized images and a lot more information about the kit are available on flickr. And if you enjoyed this article, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop”.

visit tronixlabs.com

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in electronics, kit review, talking electronics, tronixstuff

Kit Review – “Short Circuits” 3 Digit Counter

Introduction

Time for another kit review and in this instalment we have a look at the “3 digit counter” kit from Tronixlabs. This is part of a much larger series of kits that are described in a three volume set of educational books titled “Short Circuits”.

Aimed at the younger readers or anyone who has an interest in learning electronics, these books (available from Tronixlabs) are well written and with some study and practice the reader will make a large variety of projects and learn quite a bit. They could be considered as a worthy 21st-century replacement to the old Dick Smith “Funway…” guides.

The purpose of this kit is to give you a device which can count upwards between zero and 999 – which can be used for various purposes and also of course to learn about digital electronics.

Assembly

The kit arrives in typical retail fashion:

Jaycar Short Circuits Counter Kit packaging

Everything you need to make the counter is included except for the instructions – which are found in the “Short Circuits” volume two book – and IC sockets. Kits for beginners with should come with IC sockets.

Jaycar Short Circuits Counter Kit contents

The components are separated neatly in the bag above, and it was interesting to see the use of zero ohm resistors for the two links on the board:

KJ8234 Jaycar Short Circuits Counter Kit components

The PCB is excellent. The silk screening and solder-mask is very well done.

KJ8234 Jaycar Short Circuits Counter Kit PCB top

Jaycar Short Circuits Counter Kit PCB bottom KJ8234

Furthermore I was really, really impressed with the level of detail with the drilling. The designer has allowed for components with different pin spacing – for example the 100 nF capacitor and transistors as shown below:

Jaycar Short Circuits Counter Kit PCB detail KJ8234

The instructions in the book are very clear and are written in an approachable fashion:

Jaycar Short Circuits Counter Kit instructions KJ8234

Jaycar Short Circuits Counter Kit instructions two KJ8234

There’s also a detailed explanation on how the circuit works, some interesting BCD to decimal notes, examples of use (slot cars!) and a neat diagram showing how to mount the kit in a box using various parts from Jaycar – so you’re not left on your own.

Construction went well, starting with the low-profile parts:

Jaycar Short Circuits Counter Kit assembly 1 KJ8234

… then the semiconductors:

Jaycar Short Circuits Counter Kit assembly 2 KJ8234

… then the higher-profile parts and we’re finished:

Jaycar Short Circuits Counter Kit assembly finished KJ8234

There wasn’t any difficulty at all, and the counter worked first time. Although I’m not a new user, the quality of PCB and instructions would have been a contributing factor to the success of the kit.

How it works

The input signal for the counter (in this case a button controlling current from the supply rail) is “squared-up” by an MC14093 schmitt-trigger IC, which then feeds a MC14553 BCD counter IC, which counts and then feeds the results to a 4511 BCD to 7-segment converter to drive the LED digits which are multiplexed by the MC14553. For the schematic and details please refer to the book. Operation is simple, and demonstrated in the following video:

However you can feed the counter an external signal, by simply applying it to the input section of the circuit. After a quick modification:

Jaycar Short Circuits Counter Kit counter input KJ8234

… it was ready to be connected to a function generator. In the following video we send pulses with a varying frequency up to 2 kHz:

Conclusion

This is a neat kit, works well and with the accompanying book makes a good explanation of a popular digital electronics subject. There aren’t many good “electronics for beginners” books on the market any more, however the “Short Circuits” range fit the bill.

And finally a plug for our own store – tronixlabs.com – which along with being Australia’s #1 Adafruit distributor, also offers a growing range and Australia’s best value for supported hobbyist electronics from Altronics, Jaycar, DFRobot, Freetronics, Seeedstudio and much much more.

visit tronixlabs.com

As always, have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website.

Posted in education, electronics, kit, kit review, KJ8234, tronixlabs, tronixstuffComments (6)

Old Kit Review – Silicon Chip Mini Stereo Amplifier

Introduction

In this review of an older kit we examine the aptly-named “Mini Stereo Amplifier” from Dick Smith Electronics (catalogue number K5008), based on the article published in the October 1992 issue of Silicon Chip magazine.

The purpose of the kit is to offer a stereo 1W+1W RMS amplifier for use with portable audio devices that only used headphones, such as the typical portable tape players or newly available portable CD players. I feel old just writing that. At the time it would have been quite a useful kit, paired with some inexpensive speakers the end user would have a neat and portable sound solution. So let’s get started.

Assembly

Larger kits like this one that couldn’t be retailed on hanger cards shipped in corrugated cardboard boxes that were glued shut. They looked good but as soon as a sneaky customer tore one open “to have a look” it was ruined and hard to sell:

Dick Smith Electronics K5008 Stereo Amplifier Kit box

The amplifier kit was from the time when DSE still cared about kits, so you received the sixteen page “Guide to Kit Construction” plus the kit instructions, nasty red disclaimer sheet, feedback card, plus all the required components and the obligatory coil of solder that was usually rubbish:

Dick Smith Electronics K5008 Stereo Amplifier Kit all contents

However the completeness of the kit is outstanding, everything is included for completion including an enclosure and handy front panel sticker:

Dick Smith Electronics K5008 Stereo Amplifier Kit enclosure face sticker

… all the sockets, plenty of jumper wire and even the rubber feet:

Dick Smith Electronics K5008 Stereo Amplifier Kit components

The PCB is from the old-school of design – without any silk-screening or solder mask:

Dick Smith Electronics K5008 Stereo Amplifier Kit PCB front

Dick Smith Electronics K5008 Stereo Amplifier Kit PCB rear

However the instructions are quite clear so you can figure out the component placement easily. Which brings us to that point – all the components went in with ease:

Dick Smith Electronics K5008 Stereo Amplifier Kit PCB partial assembly

… then it was a matter of wiring in the sockets, volume potentiometer and power switch:

Dick Smith Electronics K5008 Stereo Amplifier Kit socket wiring

Instead of using a 3.5mm phono socket for power input, I used a 9V battery snap instead. The amplifier can run on voltages down to 1.8V so it will do for the limited use I have in mind for the amplifier. However in the excitement of assembly I forgot the power switch:

Dick Smith Electronics K5008 Stereo Amplifier Kit PCB forgot the switch

However it wasn’t any effort to rectify that. You will also notice three links on the PCB, which I fitted instead of making coils (more on this later). So at that point the soldering work is finished:

Dick Smith Electronics K5008 Stereo Amplifier Kit PCB finished

Now to drill out the holes on the faceplate. Instead of tapering out the slots on the side of the housing, I just drilled all the holes on the front panel:

Dick Smith Electronics K5008 Stereo Amplifier Kit panel

Turns out the adhesive on the front panel sticker had lost its mojo, so I might head off and get some white-on-black tape for the label maker. However in the meanwhile we have one finished mini stereo amplifier, which reminds me of an old grade seven electronics project:

Dick Smith Electronics K5008 Stereo Amplifier Kit finished

How it works

The amplifier is based on the STMicro TDA2822M (data sheet .pdf) dual low-voltage amplifier IC. In fact the circuit is a slight modification of the stereo example in the data sheet. As mentioned earlier, the benefit of this IC is that it can operate on voltates down to 1.8V, however to reach the maximum power output of 1W per channel into 8Ω loads you need a 9V supply. The output will drop to around 300 mW at 6V.

Finally the Silicon Chip design calls for a triplet of coils, one each on the stereo input wires – used to prevent the RF signal being “shunted away” from the amplifier inputs. The idea behind that was some portable radios used the headphones as an antenna, however we’ll use it with the audio out from a mobile phone so it was easier to skip hand-winding the coils and just put links in the PCB.

Using the Amplifier

The purpose of this kit was to have some sound while working in the garage, so I’ve fitted a pair of cheap 1W 8Ω speakers each to a length of wire and a 3.5mm plug as shown in the image above. And for that purpose, it works very well. In hindsight it turns out the speakers were rated at 1W peak not RMS, however they still sound great.

Conclusion

Another kit review over. This is a genuinely useful kit and a real shame you can’t buy one today. And again – to those who have been asking me privately, no I don’t have a secret line to some underground warehouse of old kits – just keep an eye out on ebay as they pop up now and again. Full-sized images and much more information about the kit are available on flickr.

And while you’re here – are you interested in Arduino? Check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in DSE, kit review, tronixstuffComments (2)

Kit Review – Altronics 3 Digit Counter Module

Introduction

In this review we examine the three digit counter module kit from Tronixlabs. The purpose of this kit is to allow you to … count things. You feed it a pulse, which it counts on the rising edge of the signal. You can have it count up or down, and each kit includes three digits.

You can add more digits, in groups of three with a maximum of thirty digits. Plus it’s based on simple digital electronics (no microcontrollers here) so there’s some learning afoot as well. Designed by Graham Cattley the kit was first described in the now-defunct (thanks Graham) January 1998 issue of Electronics Australia magazine.

Assembly

The kit arrives in the typical retail fashion:

Altronics K2505 Counter Module Kit

And includes the magazine article reprint along with an “electronics reference sheet” which covers many useful topics such as resistor colour codes, various formulae, PCB track widths, pinouts and more. There is also a small addendum which uses two extra (and included) diodes for input protection on the clock signal:

Altronics K2505 Counter Module Kit instructions

The counter is ideally designed to be mounted inside an enclosure of your own choosing, so everything required to build a working counter is included however that’s it:

Altronics K2505 Counter Module Kit parts

No IC sockets, however I decided to live dangerously and not use them – the ICs are common and easily found. The PCBs have a good solder mask and silk screen:

Altronics K2505 Counter Module Kit PCBs

Altronics K2505 Counter Module Kit PCBs rear

With four PCBs (one each for a digit control and one for the displays) the best way to start was to get the common parts out of the way and fitted, such as the current-limiting resistors, links, ICs, capacitors and the display module. The supplied current-limiting resistors are for use with a 9V DC supply, however details for other values are provided in the instructions:

Altronics K2505 Counter Module Kit

Altronics K2505 Counter Module Kit

Altronics K2505 Counter Module Kit

At this point you put one of the control boards aside, and then start fitting the other two to the display board. This involves holding the two at ninety degrees then soldering the PCB pads to the SIL pins on the back of the display board. Starting with the control board for the hundreds digit first:

Altronics K2505 Counter Module Kit

Altronics K2505 Counter Module Kit

… at this stage you can power the board for a quick test:

Altronics K2505 Counter Module Kit

… then fit the other control board for the tens digit and repeat:

Altronics K2505 Counter Module Kit

Now it’s time to work with the third control board. This one looks after the one’s column and also a few features of the board. Several functions such as display blanking, latch (freeze the display while still counting) and gate (start or stop counting) can be controlled and require resistors fitted to this board which are detailed in the instructions.

Finally, several lengths of wire (included) are soldered to this board so that they can run through the other two to carry signals such as 5V, GND, latch, reset, gate and so on:

Altronics K2505 Counter Module Kit

These wires can then be pulled through and soldered to the matching pads once the last board has been soldered to the display board:

Altronics K2505 Counter Module Kit

 You also need to run separate wires between the carry-out and clock-in pins between the digit control boards (the curved ones between the PCBs):

Altronics K2505 Counter Module Kit

For real-life use you also need some robust connections for the power, clock, reset lines, etc., however for demonstration use I just used alligator clips. Once completed a quick power-up showed the LEDs all working:

Altronics K2505 Counter Module Kit

How it works

Each digit is driven by a common IC pairing – the  4029 (data sheet) is a presettable up/down counter with a BCD (binary-coded decimal) output which feeds a 4511 (data sheet) that converts the BCD signal into outputs for a 7-segment LED display. You can count at any readable speed, and I threw a 2 kHz square-wave at the counter and it didn’t miss a beat. By default the units count upwards, however by setting one pin on the board LOW you can count downwards.

Operation

Using the counters is a simple matter of connecting power, the signal to count and deciding upon display blanking and the direction of counting. Here’s a quick video of counting up, and here it is counting back down.

Conclusion

This is a neat kit that can be used to count pulses from almost anything. Although some care needs to be taken when soldering, this isn’t anything that cannot be overcome without a little patience and diligence. So if you need to count something, get one or more of these kits from Tronixlabs Australia. Full-sized images are available on flickr. And while you’re here – are you interested in Arduino? Check out my book “Arduino Workshop” from No Starch Press – also available from Tronixlabs.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in altronics, cmos, counter, K2505, kit, kit review, LED, tronixlabs, tronixstuffComments (1)

Old Kit Review – Diesel Sound Simulator for Model Railroads

Introduction

In this review of an older kit (circa 1993~1997) we examine the Diesel Sound Simulator for Model Railroads kit from (the now defunct) Dick Smith Electronics, based on the article published in the December 1992 issue of Silicon Chip magazine.

The purpose of this kit is to give you a small circuit which can fit in a HO scale (or larger) locomotive, or hidden underneath the layout – that can emulate the rumbling of a diesel-electric locomotive to increase the realism of a train. However the kit is designed for use with a PWM train controller (also devised by Silicon Chip!) so not for the simple direct-DC drive layouts.

K3030 diesel sound simulator kit

Assembly

The diesel sound kit was from the time when DSE still cared about kits, so you received the sixteen page “Guide to Kit Construction” plus the kit instructions, nasty red disclaimer sheet, feedback card, plus all the required components and the obligatory coil of solder that was usually rubbish:

K3030 diesel sound simulator kit contents

Everything required to get going is included, except IC sockets. My theory is it’s cheaper to use your own sockets than source older CMOS/TTL later on if you want to reuse the ICs, so sockets are now mandatory here:

K3030 diesel sound simulator kit parts

The PCB is from the old school of “figure-it-out-yourself”, no fancy silk-screening here:

K3030 diesel sound simulator kit PCB

K3030 diesel sound simulator kit PCB bottom

Notice the five horizontal pads between the two ICs – these were for wire bridges in case you needed to break the PCB in two to fit inside your locomotive.

Actual assembly was straight-forward, all the components went in without any issues. Having two links under IC2 was a little annoying, however a short while later the PCB was finished and the speaker attached:

K3030 diesel sound simulator kit finished

How it works

As mentioned earlier this diesel sound kit was designed for use with the Silicon Chip train PWM controller, so the design is a little different than expected. It can handle a voltage of around 20 V, and the sound is determined by the speed of the locomotive.

The speed is determined by the back EMF measured from the motor – and (from the manual) this is the voltage produced by the motor which opposes the current flow through it and this voltage is directly proportional to speed.

Not having a 20V DC PWM supply laying about I knocked up an Arduino to PWM a 20V DC supply via an N-MOSFET module and experimented with the duty cycle to see what sort of noises could be possible. The output was affected somewhat by the supply voltage, however seemed a little higher in pitch than expected.

You can listen to the results in the following video:

I reckon the sound from around the twenty second mark isn’t a bad idle noise, however in general not that great. The results will ultimately be a function of a lower duty-cycle than I could create at the time and the values of R1 and R2 used in the kit.

 Conclusion

Another kit review over. With some time spent experimenting you could generate the required diesel sounds, a Paxman-Valenta it isn’t… but it was a fun kit and I’m sure it was well-received at the time. To those who have been asking me privately, no I don’t have a secret line to some underground warehouse of old kits – just keep an eye out on ebay and they pop up now and again. Full-sized images and much more information about the kit are available on flickr.

And while you’re here – are you interested in Arduino? Check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in DSE, electronics, K3030, kit, kit review, model railway, tronixstuffComments (2)

Kit review – Altronics Logic Probe Mk II

Introduction

Every month Australian electronics magazine Silicon Chip publishes a few projects, and in this kit review we’ll look at an older but still current example from August 2004 – the 3-state Logic Probe Kit (Mk II). This is an inexpensive piece of test equipment that’s useful when checking digital logic states and as a kit, great for beginners. Avid readers of my kit reviews may remember the SMD version we examined in June… well it wasn’t that much of a success due to the size of the parts. However this through-hole version has been quite successful, so keep reading to find out more

Assembly

The kit is packaged in typical form, without any surprises:

bag

 In typical Altronics fashion, an updated assembly guide is provided along with a general reference to common electronics topics:

bagcontents

 All the required parts are included – except for a 14-pin IC socket and two CR2016 batteries.

parts

 The PCB makes soldering easy with the silk-screen and solder mask:

pcbtop

 However the resistor numbering is a bit out of whack, a few R-numbers are skipped. So before soldering, measure and line up all the resistors in numbered order – doing so will reduce the chance of fitting them in the wrong spot.

pcbbottom

When it comes time to solder the power switch on the end, it’s necessary to clip off two tabs – one at each end of the switch. However this isn’t a problem:

solderswitchon

Soldering in the rest of the components wasn’t any effort at all, they’ve been spaced around the PCB nicely:

gettingthere

 Once they’re in, it’s time to insert the pins that hold the probe (shown on the left below):

pinsforprobe

 A full-sized probe is included with the kit, which you cut down with a hacksaw to allow it to fit on the end of the PCB. Then solder a short wire from the tip’s collar and run it through the body as such:

pinsforprobe2

 At this point, it’s time to break out the butane torch:

blowtorch

… with which you melt down the heatshrink over the tip, then fit it to the PCB and solder the probe wire:

testing

At this point it’s wise to fit the batteries and test that the probe works, as the next stage is to heatshrink the entire circuit to the left of the LEDs:

finished

Use

Using the probe is incredibly simple – however note that it’s designed for working with 5V logic. If you need to use higher voltages the probe can be assembled with slightly different circuit to take care of that eventuality. Moving forward simply clip the lead to GND on the circuit under test, then probe where you want to measure. The LEDs will indicate either HIGH, LOW or the PULSE LED will light when a fault is apparent, or other need for further research into the circuit. Here’s a quick demonstration probing a signal from an Arduino board:

Conclusion

This through-hole version of the logic probe kit was much easier to construct than the SMD version, and worked first time. A logic probe itself is a very useful tool to have and I highly recommend this kit for the beginner who enjoys projects and is growing their stable of test equipment on a budget. You can find the kit at my store – Tronixlabs Australia.

Full-sized images available on flickr.  And if you made it this far – check out my book “Arduino Workshop” from No Starch Press.

Finally, check out tronixlabs.com.au – which along with being Australia’s #1 Adafruit distributor, also offers a growing range and great value for supported hobbyist electronics from Altronics, DFRobot, Freetronics, Jaycar, Pololu and much much more.

visit tronixlabs.com

As always, have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website.

Posted in altronics, K2586, kit, kit review, logic probe, silicon chip, test equipment, tronixstuffComments (2)

Australian Electronics Nostalgia – Talking Electronics Kits

Introduction

From 1981, Australian electrical engineer Colin Mitchell started publishing his home-grown electronics magazine “Talking Electronics”. His goal was to get people interested and learning about electronics, and more so with a focus on digital electronics. It was (and still is) a lofty goal – in which he succeeded. From a couple of rooms in his home the magazine flourished, and many projects described within were sold as kits. At one stage there were over 150 Talking Electronics kits on the market. You could find the books and kits in retail outlets such as Dick Smith Electronics, and for a short while there was a TE store in Moorabbin (Victoria). Colin and the team’s style of writing was easy to read and very understandable – but don’t take my word for it, you can download the magazines from his website (they’re near the bottom of the left column). Dave Jones recently interviewed Colin, and you can watch those for much more background information.

Over fifteen issues you could learn about blinking LEDs all the way to making your own expandable Z80 board computer, and some of the kits may still be available. Colin also published a series of tutorial books on electronics, and also single-magazine projects. And thus the subjects of our review … we came across the first of these single-issue projects from 1981 – the Mini Frequency Counter (then afterwards we have another kit):

cover

How great is that? The PCB comes with the magazine. This is what set TE apart from the rest, and helped people learn by actually making it easy to build what was described in the magazine instead of just reading about it. For 1981 the PCB was quite good – they were silk-screened which was quite rare at the time:

pcb

pcbrear

And if you weren’t quite ready, the magazine also included details of a square-wave oscillator to make and a 52-page short course in digital electronics. However back to the kit…

Assembly

The kit uses common parts and I hoard CMOS ICs so building wasn’t a problem. This (original) version of the kit used LEDs instead of 7-segment displays (which were expensive at the time) so there was plenty of  careful soldering to do:

LEDsin

And after a while the counter started to come together. I used IC sockets just in case:

almostthere

The rest was straight-forward, and before long 9 V was supplied, and we found success:

powerup

To be honest progress floundered for about an hour at this point – the display wouldn’t budge off zero. After checking the multi-vibrator output, calibrating the RC circuits and finally tracing out the circuit with a continuity tester, it turned out one of the links just wasn’t soldered in far enough – and the IC socket for the 4047 was broken So a new link and directly fitting the 4047 fixed it. You live and learn.

Operation

So – we now have a frequency counter that’s good for 100 Hz to the megahertz range, with a minimum of parts. Younger, non-microcontroller people may wonder how that is possible – so here’s the schematic:

schematic

The counter works by using a multi-vibrator using a CD4047 to generate a square-wave at 50, 500 and 5 kHz, and the three trimpots are adjusted to calibrate the output. The incoming pulses to measure are fed to the 4026 decade counter/divider ICs. Three of these operate in tandem and each divide the incoming count by ten – and display or reset by the alternating signal from the 4047. However for larger frequencies (above 900 Hz) you need to change the frequency fed to the display circuit in order to display the higher (left-most) digits of the result. A jumper wire is used to select the required level (however if you mounted the kit in a case, a knob or switch could be used).

For example, if you’re measuring 3.456 MHz you start with the jumper on H and the display reads 345 – then you switch to M to read 456 – then you switch to the L jumper and read 560, giving you 3456000 Hz. If desired, you can extend the kit with another PCB to create a 5-digit display. The counter won’t be winning any precision contests – however it has two purposes, which are fulfilled very well. It gives the reader an inexpensive piece of test equipment that works reasonably well, and a fully-documented project so the reader can understand how it works (and more).

And for the curious –  here it is in action:

[Update 20/07/2013] Siren Kit

Found another kit last week, the Talking Electronics “DIY Kit #31 – 9V siren”. It’s an effective and loud siren with true rise and fall, unlike other kits of the era that alternated between two fixed tones. The packaging was quite strong and idea for mail-order at the time:

kitbox

The label sells the product (and shows the age):

kitlabel

The kit included every part required to work, apart from a PP3 battery, and a single instruction sheet with a good explanation of how the circuit works, and some data about the LM358:

kitparts

… and as usual the PCB was ahead of its’ time with full silk-screen and solder mask:

pcbtop

sirenpcbbottom

Assembly was quite straight-forward. The design is quite compact, so a lot of vertical resistor mounting was necessary due to the lack of space. However it was refreshing to not have any links to fit. After around twenty minutes of relaxed construction, it was ready to test:

PCBfinished

finished

It’s a 1/2 watt speaker, however much louder than originally anticipated:

Once again, another complete and well-produced kit.

Conclusion

That was a lot of fun, and I’m off to make the matching square-wave oscillator for the frequency counter. Kudos to Colin for all those years of publication and helping people learn. Lots of companies bang on about offering tutorials and information on the Internet for free, but Colin has been doing it for over ten years. Check out his Talking Electronics website for a huge variety of knowledge, an excellent electronics course you can get on CD – and go easy on him if you have any questions.

Full-sized images available on flickr. This kit was purchased without notifying the supplier.

And if you made it this far – check out my new book “Arduino Workshop” from No Starch Press.

LEDborder

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in australia, counter, digital, electronics, frequency, history, kit review, learning electronics, magazine, talking, talking electronics, test equipment, tronixstuff, vintageComments (8)

Review – LBE “Magpie” Arduino-compatible board

In this article we review the “Magpie” Arduino Uno-compatible board from Little Bird Electronics.

Introduction

We have a new board to review – the “Magpie” board from Little Bird Electronics in Australia. It seems that a new Arduino-compatible board enters the market every week, thanks to the open-source nature of the platform and the availability of rapid manufacturing. However the Magpie isn’t just any old Arduino Uno knock-off, it has something which helps it stand out from the crowd – status LEDs on every digital and analogue I/O pin. You can see them between the stacking header sockets and the silk-screen labels. For example:

topss

and for the curious, the bottom of the Magpie:

bottomss

At first glance you might think “why’d they bother doing that? I could just wire up some LEDs myself”. True. However having them on the board speeds up the debugging process as you can see when an output is HIGH or LOW – and in the case of an input pin, whether a current is present or not. For the curious the LEDs are each controlled by a 2N7002 MOSFET with the gate connected to the I/O pin, for example:

mosfets

An LED will illuminate as long as the gate voltage is higher than the threshold voltage – no matter the status of the particular I/O pin. And if an I/O pin is left floating it may trigger the LED if the threshold voltage is exceeded at the gate. Therefore when using the Magpie it would be a good idea to set all the pins to LOW that aren’t required for your particular sketch. Even if you remove and reapply power the floating will still be prevalent, and indicated visually – for example:

float

Nevertheless you can sort that out in void setup(), and then the benefits of the LEDs become apparent. Consider the following quick demonstration sketch:

… and the results are demonstrated in the following video:

Apart from the LEDs the Magpie offers identical function to that of an Arduino Uno R2 – except the USB microcontroller is an Atmel 16U2 instead of an 8U2, and the USB socket is a mini-USB and not the full-size type.  For the curious you can download the Magpie design files from the product page.

Conclusion

Another Arduino-compatible board. Having those LEDs on the board really does save you if in a hurry to test or check something.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

 The Magpie board used in this article was a promotional consideration supplied by Little Bird Electronics.

Posted in arduino, clone, compatible, magpie, review, tronixstuff, tutorial, unoComments (5)

Australian Electronics – David Jones interviews Colin Mitchell

Welcome back

In this post I would like to share a series of interviews conducted by Dave Jones from eevblog.com. Dave interviews Colin Mitchell from Talking Electronics. Throughout the 1980s and onwards, Colin published a range of electronics magazines, tutorials and a plethora of electronics kits – of which many are still available today. Personally I was a great fan of the TE products, and sold many of his books through my past retail career with DSE. I hope you enjoy these interviews, and if not – stay tuned for upcoming articles. Furthermore, I’ve reviewed one of the classic TE kits.

Once again, thanks to Dave Jones and of course Colin Mitchell from Talking Electronics for their interview and various insights.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in australia, education, electronics, history, talking electronicsComments (3)

Tutorial: Control AC outlets via SMS

Learn how to control AC outlets via SMS text message. This is chapter thirty-three of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 02/03/2013

Assumed understanding for this article is found in part one. If you have not already done so, please read and understand it.

In this chapter we will continue with the use of the SM5100 cellular shield to turn digital outputs on and off via SMS. However please read chapters twenty-six and twenty-seven first if you are unfamiliar with using the GSM shield with Arduino. As an extension of chapter twenty-seven, we will use our Arduino to turn on or off AC outlets via a common remote-control AC outlet pack. Please note this is more of a commentary of my own experience, and not an exact tutorial. In other words, by reading this I hope you will gain some ideas into doing the necessary modifications yourself and in your own way.

Firstly, we need some remote-control AC outlets. Most electrical stores or giant retail warehouses may have something like this:

originaloutletsss

Nothing too original, just a wireless remote control that can switch on or off receiver outlets on a choice of four radio frequencies. Before moving forward I would like to acknowledge that this article was inspired by the wonderful book Practical Arduino – Cool Projects for Open Source Hardware by Jon Oxer and Hugh Blemings. In chapter two an appliance remote-control system is devised using a similar system.

At first glance the theory behind this project is quite simple – using the hardware in example 27.2, instead of controlling LEDs, activate the buttons on the wireless remote control for the AC outlets – leaving us with AC outlets controlled via SMS. However there are a few things to keep in mind and as discovered during the process, various pitfalls as well.

Before voiding the warranty on your remote control, it would be wise to test the range of the remote control to ensure it will actually work in your situation. I found this was made a lot easier by connecting a radio to the remote outlet – then you can hear when the outlet is on or off. If this is successful, make a note of the amount of time required to press the on and off buttons – as we need to control the delay in our Arduino sketch.

The next step is to crack open the remote control:

originalremotess

… and see what we have to work with:

remotepcbss

Straight away there are two very annoying things – the first being the required power supply – 12 volts; and the second being the type of button contacts on the PCB. As you can see above we only have some minute PCB tracks to solder our wires to. It would be infinitely preferable to have a remote control that uses actual buttons soldered into a PCB, as you can easily desolder and replace them with wires to our Arduino system. However unless you can casually tear open the remote control packaging in the store before purchase, it can be difficult to determine the type of buttons in the remote.

As you can see in the photo above, there is an off and on pad/button each for four channels of receiver. In my example we will only use two of them to save time and space. The next question to solve is how to interface the Arduino digital outputs with the remote control. In Practical Arduino, the authors have used relays, but I don’t have any of those in stock. However I do have a quantity of common 4N25 optocouplers, so will use those instead. An optocoupler can be thought of as an electronic switch that is isolated from what is it controlling – see my article on optocouplers for more information.

Four optocouplers will be required, two for each radio channel. To mount them and the associated circuitry, we will use a blank protoshield and build the Arduino-remote control interface onto the shield. The circuitry for the optocoupler for each switch is very simple, we just need four of the following:

As the LED inside the optocoupler has a forward voltage of 1.2 volts at 10mA, the 390 ohm resistor is required as our Arduino digital out is 5 volts. Dout is connected to the particular digital out pin from the Arduino board. Pins 4 and 5 on the optocoupler are connected to each side of the button contact on our remote control.

The next consideration is the power supply. The remote control theoretically needs 12 volts, however the included battery only measured just over nine. However for the optimum range, the full 12 should be supplied. To save worrying about the battery, our example will provide 12V to the remote control. Furthermore, we also need to supply 5 volts at a higher current rating that can be supplied by our Arduino. In the previous GSM chapters, I have emphasised that the GSM shield can possibly draw up to two amps in current. So once again, please ensure your power supply can deliver the required amount of current. From experience in my location, I know that the GSM shield draws around 400~600 milliamps of current – which makes things smaller and less complex.

The project will be supplied 12 volts via a small TO-92 style 78L12 regulator, and 5 volts via a standard TO-220 style 7805 regulator. You could always use a 7812, the 78L12 was used as the current demand is lower and the casing is smaller. The power for the whole project will come from a 15V DC 1.5A power supply. So our project’s power supply schematic will be as follows:

Now to mount the optocouplers and the power circuitry on the blank protoshield. Like most things in life it helps to make a plan before moving forward. I like to use graph paper, each square representing a hole on the protoshield, to plan the component layout. For example:

It isn’t much, but it can really help. Don’t use mine – create your own, doing so is good practice. After checking the plan over, it is a simple task to get the shield together. Here is my prototype example:

shieldss

It isn’t neat, but it works. The header pins are used to make connecting the wires a little easier, and the pins on the right hand side are used to import the 15V and export 12V for the remote. While the soldering iron is hot, the wires need to be soldered to the remote control. Due to the unfortunate size of the PCB tracks, there wasn’t much space to work with:

txsolder1ss

But with time and patience, the wiring was attached:

txsolder2ss

Again, as this is a prototype the aesthetics of the modification are not that relevant. Be careful when handling the remote, as any force on the wiring can force the soldered wire up and break the PCB track. After soldering each pair of wires to the button pads, use the continuity function of a multimeter to check for shorts and adjust your work if necessary.

At this stage the AC remote control shield prototype is complete. It can be tested with a simple sketch to turn on and off the related digital outputs. For example, the following sketch will turn on and off each outlet in sequence:

Now to get connected with our GSM shield. It is a simple task to insert the remote shield over the GSM shield combination, and to connect the appropriate power supply and (for example) GSM aerial. The control sketch is a slight modification of example 27.2, and is shown below

The variable pressdelay stores the amount of time in milliseconds to ‘press’ a remote control button. To control our outlets, we send a text message using the following syntax:

Where a/b are remote channels one and two, and x is replaced with 0 for off and 1 for on.

So there you have it – controlling almost any AC powered device via text message from a cellular phone. Imagine trying to do that ten, or even five years ago. As always, now it is up to you and your imagination to find something to control or get up to other shenanigans.

LEDborder

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in AC power, arduino, CEL-00675, CEL-09607, cellphone hacking, cellular, GSM, hardware hacking, lesson, SM5100, SMS, tutorial

Kit review – Evil Mad Science Larson Scanner

Hello readers

Time yet again for another kit review. Today’s kit is the Larson Scanner from Evil Mad Science. What a different name for a company; their byline is “DIY and open source hardware for art, education and world domination”. Art? Yes. Education? Definitely. World domination? Possibly – you could use the blinking LEDs to hypnotise the less intelligent world leaders out there.

Anyhow, what is a Larson Scanner? Named in honour of Glen A. Larson the creator of television shows such as Battlestar Galactica and Knight Rider – as this kit recreates the left and right blinking motion used in props from those television shows. For example:

The kit itself is quite inexpensive, easy to assemble – yet can be as complex as you want it to be. More about that later, for now let’s put one together and see how it performs. There are two versions of the kit, one with 5mm clear LEDs and our review model with 10mm diffused red LEDs. The kit arrives inside a huge resealable anti-static bag, as such:

1ss

Upon opening the bag we have the following parts (there was an extra LED and resistor, thanks):

4ss

… the PCB:

3ss

… which is nicely done with a good silk-screen and solder mask. And finally:

5ss

A very handy item – a battery box with power switch. The kit is powered by 2 x AA cells (not included!). And finally, the instructions:

2ss

At this point you can see that this kit is designed for the beginner in mind. The instructions are easy to read, clear, and actually very well done. If you are looking for a kit to get someone interested in electronics and to practice their soldering, you could do a lot worse than use this kit. Construction was very easy, starting with the resistors:

6ss

followed by the capacitor and button:

7ss

then the microcontroller:

8ss

… no IC socket. For a beginners’ kit, perhaps one should have been included. Next was the battery box. Some clever thinking has seen holes in the PCB to run the wires through before soldering into the board – doing so provides a good strain relief for them:

9ss

… and finally the LEDs. Beginners may solder them in one at a time:

10ss

however it is quicker to line them up all at once than solder in one batch:

11ss

… which leaves us with the final product:

13ss

Operation is very simple – the power switch is on the battery box. The button on the PCB controls the speed of LED scrolling, and if held down switches the brightness between low and high. Now for some action video of the Larson Scanner in operation:


Well that really was fun, a nice change from the usual things around here.

But wait, there’s more… although the Larson Scanner is a good training kit, it can also function in other interesting ways. The kit is completely open-source, you can download the PCB layout file, circuit schematic and microcontroller code. Get two or more and link them together to make a really wide LED display – expansion instructions are available from here. If you solder in a 6-pin PCB header to the area marked J1 on the PCB, you can reprogram the microcontroller using an STK500-compatible programmer.

After sitting my Larson Scanner next to the computer tower for a few minutes, I had contemplated fitting it into a 5.25″ drive bay to make my own Cylon PC, however that might be a little over the top. However my PC case has some dust filters on the front, which would allow LEDs to shine through in a nicely subdued way. Mounting the Larson Scanner PCB inside the computer case will be simple, and power can be sourced from the computer power supply – 5V is available from a disk drive power lead.

If you are going to modify your PC in a similar fashion, please read my disclaimer under “boring stuff” first.

The Larson Scanner can run on 3.3V without any alteration to the supplied components. What needs to be done is to use a voltage regulator to convert the 5V down to 3.3V. My example has used a 78L33 equivalent, the TI LP2950 as it is in stock. The power comes from a drive power cable splitter as such:

splitss

You may have a spare power plug in your machine, so can tap from that. 5V is the red lead, and GND is the adjacent black lead. Don’t use yellow – it is 12V. It is then a simple matter of running 5V from the red lead to pin 1 of the regulator, GND from the Larson Scanner and PC together to pin 2, and 3.3V out from the regulator to the PCB 3.3V. Insulation is important with this kind of work, so use plenty of heatshrink:

ldo1ss

… then cover the whole lot up:

ldo2ss

Now to locate a free power plug in the machine. It has been a while since opening the machine – time for a dust clean up as well:

ldo3ss

Mounting the PCB is a temporary affair until I can find some insulated mounting  standoffs:

ldo4ss

However it was worth the effort, the following video clip shows the results in action:


So there you have it. The Larson Scanner is an ideal kit for the beginner, lover of blinking LEDs, and anyone else that wants to have some easy blinking fun. You can buy Larson Scanner kits in Australia from Little Bird Electronics, or directly from Evil Mad Science for those elsewhere.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow me on twitter or facebook, or join our Google Group for further discussion.

High resolution images are available on flickr.

[Note – The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

Posted in evil mad science, kit review, larson scanner, learning electronics, tutorialComments (0)

March 2011 Competition Results

Competition over!

Posted in competitionComments (0)

Update – Upcoming Electronics Industry Documentary

Hello readers

Today I am going to introduce something quite different, yet hopefully interesting to you out there. The renowned director and cinematographer Karl von Muller has just released the roll-call trailer for his upcoming documentary titled “State of Electronics” – a discussion on the Electronics Industry in Australia. Although the focus is on the Australian electronics scene, much of the content and discourse within the documentary can be related to by those from many other countries.

However, Karl can explain it better:

After several months of researching, interviewing and filming, I’m excited to present the first public Trailer to my new Documentary “State of Electronics” – A discussion on the Electronics Industry in Australia. Even though the documentary is focused on Australian Electronics Design and Manufacture, much of it applies to all countries from around the world.

The discussion is focused initially on the world of Hobby Electronics and how it’s decline could affect the Electronics Industry in the future. The Documentary then discusses many issues that face industry including the issue of “Repair and Recycle”, “Education”, “Surface Mount Technology”, “Globalisation”, “Opportunities” and many many more off the cuff & candid comments from Industry professionals.

The Documentary features interviews with famous Australians and Industry professionals including Dick Smith, Dave L Jones, Doug Ford, Leo Simpson, Grant Petty, Matthew Pryor, Jonathan Oxer, Andy Gelme, Andrew Griffiths, Eugene Ruffolo & Bill Petreski. In the future, I am planning to interview just a few more before the final release of the Documentary soon.

Shot completely on the Canon 5DMK2, using the Zoom H4N Audio recorder. Directed, Edited and shot by Karl von Moller, this version of the trailer is largely ungraded and only has an FCP sound mix applied. Music track is composed by Karl von Moller also. Enjoy!

Please visit karlvonmoller.com for more on the progress and information on “State of Electronics”

Here is the new roll-call trailer:

… and the original trailer for those unfamiliar with the project:

This will surely be a fascinating and insightful documentary that we are all looking forward to. Nice one Karl!

Posted in education, electronics, historyComments (0)

March 2011 Competition

Competition over!

Posted in arduino, competition, learning electronics

Tutorial: Arduino and GSM Cellular – Part Two

Continue to learn about connecting your Arduino to the cellular network with the SM5100 GSM module shield. This is chapter twenty-seven of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 02/03/2013

Assumed understanding for this article is found in part one. If you have not already done so, please read and understand it. In this instalment we continue with bare projects which you can use as a framework for your own creations.

Reach out and control something

First we will discuss how to make something happen by a simple telephone call. And the best thing is that we don’t need the the GSM module to answer the telephone call (thereby saving money) – just let the module ring a few times. How is this possible? Very easily. Recall example 26.1 – we monitored the activity of the GSM module by using our terminal software. In this case what we need to do is have our Arduino examine the text coming in from the serial output of the GSM module, and look for a particular string of characters.

When we telephone the GSM module from another number, the module returns the text as shown in the image below:

term2

We want to look for the text “RING”, as (obviously) this means that the GSM shield has recognised the ring signal from the exchange. Therefore need our Arduino to count the number of rings for the particular telephone call being made to the module. (Memories – Many years ago we would use public telephones to send messages to each other. For example, after arriving at a foreign destination we would call home and let the phone ring five times then hang up – which meant we had arrived safely). Finally, once the GSM shield has received a set number of rings, we want the Arduino to do something.

From a software perspective, we need to examine each character as it is returned from the GSM shield. Once an “R” is received, we examine the next character. If it is an “I”, we examine the next character. If it is an “N”, we examine the next character. If it is a “G”, we know an inbound call is being attempted, and one ring has occurred. We can set the number of rings to wait until out desired function is called. In the following example, when the shield is called, it will call the function doSomething() after three rings.

The function doSomething() controls two LEDs, one red, one green. Every time the GSM module is called for 3 rings, the Arduino alternately turns on or off the LEDs. Using this sketch as an example, you now have the ability to turn basically anything on or off, or call your own particular function. Another example would be to return some type of data, for example you could dial in and have the Arduino send you a text message containing temperature data.

And now for a quick video demonstration. The first call is made, and the LEDs go from red (off) to green (on). A second call is made, and the LEDs go from green (on) to red (off). Although this may seem like an over-simplified example, with your existing Ardiuno knowledge you now have the ability to run any function by calling your GSM shield.

Control Digital I/O via SMS

Now although turning one thing on or off is convenient, how can we send more control information to our GSM module? For example, control four or more digital outputs at once? These sorts of commands can be achieved by the reception and analysis of text messages.

Doing so is similar to the method we used in example 27.1. Once again, we will analyse the characters being sent from the GSM module via its serial out. However, there are two AT commands we need to send to the GSM module before we can receive SMSs, and one afterwards. The first one you already know:

Which sets the SMS mode to text. The second command is:

This command tells the GSM module to immediately send any new SMS data to the serial out. An example of this is shown in the terminal capture below:

smsrxdemo

Two text messages have been received since the module was turned on. You can see how the data is laid out. The blacked out number is the sender of the SMS. The number +61418706700 is the number for my carrier’s SMSC (short message service centre). Then we have the date and time. The next line is the contents of the text message – what we need to examine in our sketch.

The second text message in the example above is how we will structure our control SMS. Our sketch will wait for a # to come from the serial line, then consider the values after a, b, c and d – 0 for off, 1 for on. Finally, we need to send one more command to the GSM module after we have interpreted our SMS:

This deletes all the text messages from the SIM card. As there is a finite amount of storage space on the SIM, it is prudent to delete the incoming message after we have followed the instructions within. But now for our example. We will control four digital outputs, D9~12. For the sake of the exercise we are controlling an LED on each digital output, however you could do anything you like. Although the sketch may seem long and complex, it is not – just follow it through and you will see what is happening:

And now for a video demonstration:

So there you have it – controlling your Arduino digital outputs via a normal telephone or SMS. Now it is up to you and your imagination to find something to control, sensor data to return, or get up to other shenanigans.

If you enjoyed this article, you may find this of interest – controlling AC power outlets via SMS.

LEDborder

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, CEL-00675, CEL-09607, cellphone hacking, cellular, GSM, hardware hacking, lesson, microcontrollers, SM5100, SMS, tutorial

Tutorial – Arduino Uno and SM5100B GSM Cellular

Shield is now obsolete. Contact your hardware supplier for support.

Posted in arduino, CEL-00675, CEL-09607, cellphone hacking, cellular, GSM, lesson, SMS, tronixstuff, tutorial

Kit review – Sparkfun Function Generator

Hello readers

[10/09/2011 Update – It would seem that this kit has been discontinued – most likely due to the unavailability of the XR2206 function generator IC – which is a damn shame as it was a great kit. If you are ‘feeling lucky’ eBay seems to have a flood of them. Purchase at your own risk!]

Time for another kit review (anything to take the heat off from the kid-e-log!). Today we will examine the Sparkfun Function Generator kit. This is based from an original design by Nuxie and has now been given a nice thick red PCB and layout redesign. Although quite a bare-bones kit, it can provide us with the following functions:

  • sine waves
  • triangle waves
  • a 5V square wave with adjustable frequency

There are two frequency ranges to choose from, either 15~4544Hz or 4.1~659.87kHz. Your experience may vary, as these values will vary depending on the individual tolerance of your components.  The coarse and fine adjustment potentiometers do a reasonable job of adjustment, however if you were really specific perhaps a multi-turn pot could be used for the fine adjustment. With the use of a frequency counter one could calibrate this quite well.

The maximum amplitude of the sine and triangle waves is 12V peak to peak, and doing so requires a DC power supply of between 14~22 volts (it could be higher, up to 30 volts – however the included capacitors are only rated for 25V). However if you just need the 5V square-wave, or a lower amplitude, a lesser supply voltage such as 9 volts can be substituted. After running the generator from a 20V supply, the 7812 regulator started to become quite warm – a heatsink would be required for extended use. The main brains of the generator are held by the Exar XR2206 monolithic function generator IC – please see the detailed data sheet for more information.

Now what do you get? Not much, just the bare minimum once more. Everything you need and nothing you don’t …

bagpartsss

Upon turfing out the parts we are presented with:

thepartsss

Not a bad bill of materials – nice to see a DC socket for use with a plug-pack. Considering the XR2206 is somewhat expensive and rare here in the relative antipodes, an IC socket would be nice – however I have learned to just shut up and keep my own range in stock now instead of complaining. Having 5% tolerance resistors took me as a surprise at first, but considering that the kit is not really laboratory-precision equipment the tolerance should be fine. One could always measure the output and make a panel up later on.

Once again, I am impressed with the PCB from Sparkfun. Thick, heavy, a good solder mask and descriptive silk-screen:

pcbss

Which is necessary as there aren’t any instructions with the kit nor much on the Sparkfun website. The original Nuxie site does have a bit of a walk through if you like to read about things before making them. Finally, some resistors and capacitors included are so small, a decent multimeter will be necessary to read them (or at least a good magnifying glass!).

Construction was very simple, starting with the low-profile components such as resistors and capacitors:

resiscapsss

followed by the switches, terminal blocks, IC sockets and the ICs:

icsss

and finally the potentiometers:

potsss

The easiest way to solder in the pots while keeping them in line was to turn the board upside down, resting on the pots. They balance nicely and allow a quick and easy soldering job. At this point the function generator is now ready to go – after the addition of some spacers to elevate it from the bench when in use:

finishedss

Now for the obligatory demonstration video. Once again, the CRO is not in the best condition, but I hope you get the idea…


Although a very simple, barebones-style of kit (in a similar method to the JYETech Capacitance meter) this function generator will quickly knock out some functions in a hurry and at a decent price. A good kit for those who are learning to solder, perhaps a great next step from a TV-B-Gone or Simon kit. And for the more advanced among us, this kit is licensed under Creative Commons attribution+share-alike, and the full Eagle design files are available for download – so perhaps make your own? High resolution images are available on flickr.

[Note – The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

 In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in education, kit review, KIT-10015, learning electronics, oscilloscope, test equipment, XR2206Comments (0)

Kit Review – Silicon Chip Low Capacitance Meter adaptor for DMMs

Hello readers

Time again for another kit review. In the spirit of promoting all things electronic and Australian, we’re going to look at a kit that was published in our electronics magazine Silicon Chip (March 2010) – their Low-capacitance meter adaptor for DMMs. Simply put, it converts capacitance (from a theoretical 1 picofarad) to millivolts, which you can then read with almost any digital multimeter. This is useful as even more expensive multimeters (such as my Fluke 233) only measure down to 1 nanofarad (1000 picofarads). Although this kit is available on the Australian market, the retailers will export to those abroad. If you are outside Australia and having trouble sourcing one, send me an email. Moving on…

Here is our unassuming finished product:

finishedss5

Please note that this is not an open-source product, so you need to either purchase the kit of parts, or a back-issue of Silicon Chip magazine, March 2010 for the schematic and instructions. Now it is time to get started. But before that, how does it work?

Without giving too much away, a very rough explanation would be that a square wave signal is formed, then cleaned up through a Schmitt trigger-inverter. This square wave is then split into two, one signal passing through the capacitor under test and some resistors, and the other signal passing through a calibration variable capacitor and the same value resistors – thereby both signals pass through two different RC circuits. Finally the two signals are fed through a XOR gate, which creates a series of positive pulses that are a function of the capacitor under test.

Kit assembly was not that difficult, like anything just take your time, read the instructions carefully, and don’t rush things. If you are happy with your through-hole soldering skills, and have a power drill, this kit will be easy for you to work with. Unusually for some kits, this one comes with almost everything you need:

partsss3

The quality of the included housing is very good, there are metal threaded inserts for the screws; and even through the ICs are simple 74xx-series, sockets have been included. Resistors are metal film, the trimpots are enclosed multiturns – all very nice. I am a little disappointed with the housing/adhesive label combination however, in the past various kits from Jaycar would have a box with a nice silk-screened, hole-punched front panel. Such is life. The PCB is solder-masked and silk-screened, however a little less denser than PCBs from other kit suppliers:

pcbss1

And thus brings a slight issue with the housing and the PCB – either the PCB is too wide, or the box is too narrow. A quick clip of the PCB with some cutters will fix that:

filedpcbss

The instructions are quite good – they are a reprint of the magazine article, and slightly modified by the kit production company. Furthermore, the silk-screening on the PCB makes things a breeze. The simple passives were easy to install, however take care not to overheat the variable capacitor, their casings can melt rather quickly:

resiscapsss

Following that, the ICs were inserted, and the rotary switch. From experience, one should trim the shaft down to about a 25mm length before soldering it into the board. Take very good care when placing the rotary switch, there is a lump on the switch which matches the small circle at 8 o’clock on the PCB diagram. Finally, don’t forget to alter the switch so it only has four selections. Soldering it in can look difficult, but is not. Just push it into the PCB, checking it is flush, even and all the way in. Then bend a couple of the pins over, invert the PCB and solder away – as such:

solderrotaryss

Now it is time to start on the enclosure. Each end has two banana-type sockets, the left are the full binding-post, and the right are just sockets. Carefully mark where you want to start the holes – the positions are vertically half-way, and horizontally 15mm in from the edge, however double-check yourself. Always check the fit of the socket while drilling, as it is easy to go too far and make the holes too large – at which point you’ll have to buy another enclosure. Once you have the sockets fitted – on the left:

left-endss

and on the right:

right-endss

… you will need to solder the socket rear to the PCB pins (left) and a small link to the PCB pins (right). It is important to get a good, solid connection – as these sockets may come under a lot of use later on. Next it is time to start on the housing. If you can, photocopy the label so you have a drilling template:

labelsss

You will notice in the above photo one of my favourite tools, a tapered reamer. Using that, you can carefully turn a small hole into a larger hole, without risking making a mess with a drill. Again, cut the rotary switch’s shaft before soldering:

drilledboxss

And as punishment for using twitter at the same time, I had ended up drilling the back instead of the front. D’oh. However cosmetic appearance is secondary to functionality, so all is well. Next was to install the PP3 battery snap. The battery will be a tight fit, so a length of heatshrink has been supplied in order to avoid the battery case shorting with the PCB pin:

pp3snapss

And finally we have finished soldering:

donesolderingss

Now it is time for calibration. And for me to get a little cranky, which is quite rare as I am somewhat easygoing. Calibration requires three 1% tolerance capacitors, 100 pF, 1000 pF and 10000 pF. And they are not included with the kit. And can not be purchased from any of the kit retailers. So they had to be ordered from Farn… element-14 at a reasonable expense. Considering the kit production company also imports, wholesales and retails electronic components, they could have bought a volume of these special capacitors and added a few dollars to the price of the kit. Such is life. So here are the little buggers:

calibrationcapsss

From top to bottom:

  • Silvered-mica 100 picofarad 1% tolerance, element-14 # 1264880, RS # 495745;
  • Polystyrene 1000 picofarad 1% tolerance, element-14 # 9520651, RS # 495868 (silvered mica) and
  • Polystyrene 10000 picofarad 1% tolerance, element-14 # 3358951, RS # 495953 (silvered mica)

However it is worth the effort to chase them down. There is no point using this kit if you calibrate with normal capacitors; their tolerance can be as much as 20 percent either way. Thankfully the calibration process is quite simple. You will need a small, plastic flat-blade screwdriver to make the adjustments, as your body has stray energy which can alter the capacitance measurements.

Before starting, connect your multimeter to the output sockets and set the range to millivolts – then adjust the variable capacitor until you have the meter display as close to zero as possible. This is used to ‘null out’ stray capacitance. Next, set the dial to A, connect the 100 pF capacitor to the input posts, and adjust VR3 until the meter displays one volt DC – this represents 100.0 picofarads:

cal1ss

I could not for the life of me get this to 1 volt. After fitting the case at the end, I tried again with the case on with the same result. It is very important to get the capacitor as close as possible to the binding posts, with such small values stray capacitance can affect the result. However in my line of work, one-tenth of a picofarad is not relevant. For now. Next, set the dial to B, connect the 1000 pF capacitor, and adjust VR2 until the meter displays 1 volt – this represents 1000 picofarads:

cal2ss

Excellent – spot on. Unfortunately the leads on my 10000 pF capacitor were not long enough to attach into the binding posts, so that step had to be passed. I will have to re-order the correct part next week and calibrate then. However the other two setting are basically working perfectly, which is a good indication for the general performance of the kit. Kudos to Jim Rowe from Silicon Chip magazine for this design. Before closing up the enclosure, I decided to wrap the battery with some paper, as having it  rub up against other parts is not a good idea:

battpaperss

Now for a test run – time to measure the smallest capacitors I have in stock, first a 4.7 picofarad ceramic:

4p7ss

and next, a 12 picofarad ceramic:

12p0ss

Excellent, we can call these readings a success. I was also quite amazed that the tolerance of the cheap ceramic capacitors was so low. Note that in real-life, you may not be able to have the capacitor under test directly connected to the binding posts. In these cases you will need a short set of heavy-gauge leads to the test capacitor. If you do this, you will need to adjust the variable capacitor to reset the display to account for stray capacitance in the leads.

In conclusion, this kit has proved very successful, with regards to assembly, the quality of components and instructions, and of course the final result. I made a few errrors with regards to the housing, but that didn’t affect the final result. And for less than fifty Australian dollars, I have a very low value capacitance meter. However in due course I would consider the purchase of a full LCR meter for greater accuracy and ease of frequent use (some can measure down to 0.1 picofarad). But for the time being, this has been an excellent, educational  and affordable solution. You can purchase the kit directly from Jaycar. High resolution images are available on flickr.

So have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

[Note – The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

Posted in capacitance meter, jaycar, KC5493, kit review, learning electronicsComments (2)

Australian Electronics Nostalgia – “Funway Kits”

Hello readers

After viewing the trailer for Karl von Muller’s upcoming documentary State of Electronics – A discussion on the Electronics Industry in Australia, it brought back some fond memories of bashing about with a range of kits from many years ago. So today we will have a look at a few of them. But first some history (feel free to correct me here)…

In 1968 an enthusiastic man by the name of Dick Smith started a small car radio shop in Neutral Bay, Sydney. Although he had many ups and downs – through extremely hard work, marketing in ways Australia had never seen before (see the bus below), and revolutionising electronics and computer retailing in this country – he built up Dick Smith Electronics to a company so large he sold it for a huge sum and moved on to other successful ventures. You can download his biography from here.

Dick Smith Electronics’ stores were the place to go for components, a huge range of electronic kits, an interesting range of computers (in [earlier] kit and assembled form), amateur and CB radio – all the fun stuff. You would almost need a shotgun to clear the store out on a Thursday night or Saturday afternoon. There were also repair centres in each capital city and head office, that employed people to fix things for warranty service (and they would fix kits for a price as well). Before the internet one would stalk the mailbox waiting for the new catalogue to arrive. I even worked there for four years in the 1990s. Unfortunately due to market changes and carbon-based factors, the stores are now just glorified flat-screen TV and video game outlets.

However, partly to educate people (and probably to make more money), Dick Smith wrote a series of books titled “Fun Way into Electronics”, starting with the first in 1979. This entailed twenty very basic electronic circuits, such as flashing LEDs using a multivibrator, basic transistor amplifiers, and a “beer powered radio” (I wonder how many children tried that fuel cell?). The book had paper overlays which you would glue onto a piece of chipboard, and screw the components down to form a circuit. Later editions would use a plastic board with holes:

3143205539_96d689c02e_z

The Funway book was very popular (and still is with some schools, Scout groups and so on), so Dick published volume two from 1980. Finally some “real” projects – twenty kits that required soldering and could be of some real use in the world. Items such as a shortwave radio, intercom, timing devices, digital counters, and a mosquito repeller of dubiuos success. However they sold very well, and in 1984 the final volume of the Funway trilogy was published – another ten projects – “each with an integrated circuit!”

The books were illustrated in a very clear, simple way sometimes hand-drawn but very neat. I suspect some women in the books were meant to resemble associates of Dick Smith, and in general the book is a ‘snapshot’ of the times. For example, the transistor radio:

radiobikewoman

Please note that I will not email you a .pdf of any of the books mentioned, so kindly don’t ask – they’re still Copyright DSE Pty Ltd. Part of my reasoning for this article was the fact that the Funway era has now drawn to a close. Whilst recently wandering about in a Dick Smith store for some reminiscing, I noticed the remaining stock of Funway 2 kits on the clearance bench and the matching volume two books, which compelled me to rescue them.

At the register, the sales clerk asked me “Why would you want to make a radio?” … ugh

So let’s take a trip back to 1980 and see how they perform!

[Update 07/07/2013]

Wow! I found another kit – project seventeen, the LED level display. It was designed to show audio levels in a blinky form – the addition of a pair to your home or car hi-fi would put those analogue VU meters to shame whilst impressing your friends. When fitted inside the optional box and the label applied, you could be as cool as the guy below looking like he’s getting revved up for a night at the discotheque:

discodude

So time to give it a whirl. I remember this kit back in 1985 when a friend gave it to me from someone else, he cut off the LEDs for himself, and I ended up with the useless board. Thanks Tony. Well 28 years later here I am with the brand-new version:

proj17

Otherwise everything was as expected, all the parts and the poor PCB included:

parts

pcb

Construction was relatively simple but tedious, 22 resistors, 10 diodes, 10 LEDs, 11 transistors etc… just careful and steady work to get it done. This would have kept a teenager busy for a good weekend inside. After an hour and an espresso the board was populated:

board

Not wanting to chop up any audio leads to test the kit, I’ve instead put some pins on the power supply and input pairs for a quick demonstration. For a signal I’ve attached a function generator and fed a sine wave at various low frequencies. Here it is in action:

In hindsight that’s a pretty fun kit, and with some careful work it would have looked good in a contemporary audio system. It probably could have been done a lot easier with an LM3914 however the cost may have been prohibitive at the time.

Next we have Project Sixteen –  the Electronic Siren. This is basically two 555 oscillators, one for the sound, and the other for the duration – which combined with a basic amplifier make a “hee-haw” sound. This kit would have been included as a good sales add-on for the Home and Car alarm kit also described in the book. Typical of the series, when you purchased a kit it would come with the bare minimum, just enough to make it work (excluding the battery):

sirenpartsss

Naturally a full range of extras would be mentioned in the book, available from the store when required. The PCB looks like it was made at home – examining this one I can now be more grateful than ever for silk-screening and solder-masking on current PCBs:

sirenpcbss

To make annoying people easier I will add in a SPDT toggle switch, and use some IC sockets for the 555s. Assembling the kit took no time at all, the instructions were clear and easy to follow:

sirenbookss

Starting the soldering caused some flashbacks to my childhood, which were interesting. Assembling this at my age was much quicker than as a young lad – my soldering style has changed, and I also have a Fluke 233 to check the resistor and capacitor values. There was one nod to the future in the kit, the polyester capacitor was replaced by an MKT. The only reason to use the IC sockets was so I could reuse the 555s later on. Moving on, here is the finished article:

sirenfinishedss

And did it work? Absolutely – have a listen:


It is really quite loud, that 0.25 watt speaker is being pushed quite hard. According to the book you can connect a horn-speaker directly to the output. Furthermore there are suggestions on how to alter the frequency and duration of the sounds. So overall, this was an easy to assemble kit that was still some fun even to this day.

The next kit to examine is Project Eleven – FM wireless microphone. This consists of an oscillator of around 100 MHz, which receives a signal via the tiny electret microphone. The book illustration shows a Donna Summer lookalike with a guitar, however one could imagine people building these kits and using them as ‘bugs’ and generally getting up to no good:

txbookss

Again, the clear images and instruction layouts are constant throughout the book. There were two errata sheets included with the components, as the design has been altered a few times. However they were easy enough to follow, and the correct replacement parts had been included:

txbitsss

Once more the PCB was a product of the time. After having issues with the siren kit’s PCB, I gave this one a good squirt with some Servisol PCB cleaner – that made a difference when it was time to solder:

txpcbss

From a beginner’s perspective, this would have been a slightly more difficult kit to assemble, due to the all the vertical resistors and the close spacing between the components. However this was to enable budding ASIO operatives to make their ‘bug’ as small as possible. From memory this is the trickiest of them all, the rest of the Funway 2 kits had generous PCB spacing. I must admit to breaking a 470 pF ceramic capacitor, but that was my own silly fault. However at the end it all came together nicely:

txworkss

And it worked.  I have a feeling that the variable capacitor was damaged a little from heat due to the soldering process, for some insane reason DSE supplied a plastic-encased version. Later on I will replace it and see how we go. But for the meanwhile, with a 20cm aerial wire, I could get about 5 metres out of it with a brick wall in between. Considering the target market for this, that’s pretty good.

The next kit is Project Seven – Pocket Transistor Radio. This is a basic amplitude-modulation radio receiver making use of the MK484 radio-receiver IC. This is a bog-standard simple AM receiver circuit that dates back to the early 1970s. However, it is simple and uses very few parts. Originally the kit was sold without an earpiece or socket, but the last few batches included everything but the battery and a switch:

radiopartsss

Once again there were two errata sheets – one explaining the different pinouts of the MK484/ZN414 radio IC, and another showing the evolution of the radio circuit, a capacitor had been replaced with a resistor. There were a couple of tricks to assembling this kit, some pin spacings were unnecessarily close together, and the leads on the antenna coils were terribly difficult for me to discern. Thankfully the book offered some great advice – use a multimeter to determine the resistance of each coil. The coil with the lower resistance is the aerial coil, and the higher resistance is the main coil. And once again I have added a power switch. After some trepidation, the main board was finished:

rxfinishedss

Ah – where is the 9V battery? With regards to the circuit, versions as published in the book and the errata sheet are quite inefficient with regards to power usage. Let’s have a look:

radiocircuitss

As part of my electronics learning process, I like to follow the circuit through to see what is going on. The book has the power being supplied by a 9V battery, then using a 6.8V Zener diode. What was the point of that? Instead, I put a link on the PCB instead of the zener, and now the power is from a single AA cell. Much, much cheaper to run now, the receiver only draws nine milliamps of current:

And to think some people have to recharge their music players every day. The radio worked from the first time the battery was connected, and is working very well. The volume/gain is controlled by the 5k trimpot, I have this set to around half-way to a comfortable volume. The reception is highly relative to the positioning of the ferrite rod aerial, so I have locked it into place using some blutac. It receives local AM stations very well, and also some rural stations from interstate. For the price and the amount of parts, this is a very simple, easy to construct receiver with excellent power consumption – which is begging for a solar panel for daytime use. Maybe next week! So we have another success.

Update! I found another kit – the “Universal Timer”. This is basically an over-engineered 555 timer that controls a simple SPDT relay. The 555 is configured as a monostable timer, and the duration controlled by a 1 mega ohm trimpot. I have a feeling the design brief was for an egg timer, based on the illustrations:

timerbookss

Once again, the illustrations of the final product don’t bear much of a resemblance to the contents of the basic kit:

timerpartsss

Again, the PCB was quite basic and needed a good clean:

timerpcbss

Construction was quite simple, all of the parts fitted nicely where they were meant to. Not bad considering the PCB was designed around thirty years ago, and the parts are much more recent – especially the relay. To make some sort of demonstration I had to add a few extras – a power switch, the piezo buzzer, IC socket and a potentiometer instead of the trimpot:

timerfinishedss

Though once again it worked, and I actually have a use for it – a shower timer for an intelligent person who seems to forget the concept of time when in the bathroom. A quick trip to the store for a moisture-proof IP67-rated box and we’ll be set.

Unfortunately with the discontinuation of these Funway kits means another opportunity to teach people has gone. I hope you found this article interesting, and helped motivate you to expand your knowledge and those of others in the STEM (science, technology, electronics and maths) area. If you have any Funway projects to share, please get in touch. Some higher-resolution images available on flickr.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in education, electronics, funway, history, kit review, learning electronicsComments (16)

Upcoming Electronics Industry Documentary

Hello readers

Today I am going to introduce something quite different, yet hopefully interesting to you out there. The renowned director and cinematographer Karl von Muller has just released the trailer for his upcoming documentary titled “State of Electronics” – a discussion on the Electronics Industry in Australia. Although the focus is on the Australian electronics scene, much of the content and discourse within the documentary can be related to by those from many other countries.

However, Karl can explain it better:

After several months of researching, interviewing and filming, I’m excited to present the first public Trailer to my new Documentary “State of Electronics” – A discussion on the Electronics Industry in Australia. Even though the documentary is focused on Australian Electronics Design and Manufacture, much of it applies to all countries from around the world.

The discussion is focused initially on the world of Hobby Electronics and how it’s decline could affect the Electronics Industry in the future. The Documentary then discusses many issues that face industry including the issue of “Repair and Recycle”, “Education”, “Surface Mount Technology”, “Globalisation”, “Opportunities” and many many more off the cuff & candid comments from Industry professionals.

The Documentary features interviews with famous Australians and Industry professionals including Dick Smith, Dave L Jones, Doug Ford, Leo Simpson, Grant Petty, Matthew Pryor, Jonathan Oxer, Andy Gelme, Andrew Griffiths, Eugene Ruffolo & Bill Petreski. In the future, I am planning to interview just a few more before the final release of the Documentary soon.

Shot completely on the Canon 5DMK2, using the Zoom H4N Audio recorder. Directed, Edited and shot by Karl von Moller, this version of the trailer is largely ungraded and only has an FCP sound mix applied. Music track is composed by Karl von Moller also. Enjoy!

Please visit karlvonmoller.com for more on the progress and information on “State of Electronics”

Here is the trailer for your enjoyment, on Vimeo or YouTube (below):

As an Australian, an educator and an electronics enthusiast, I encourage you to view the trailer and share it with as many people as possible. If you have contacts in the broadcast media, please talk to them about this documentary and suggest it for screening.

Posted in education, electronics, historyComments (2)

Project – Let’s make Electronic Dice

In this project we make electronic dice.

Updated 18/03/2013

In this article you can learn how to make an electronic die (die is the singular of dice), using an ATmega328 with Arduino bootloader and a few inexpensive components. The reason for doing this is to introduce another object that you can build, learn from and be proud of. It is a fairly simple procedure, and at the end you will have something that is useful for a long time to come. Again this article will be a design-narrative, so please read it in full before making a die yourself.

First of all, here is a photo of my finished product.

finishedssss1

Naturally the cosmetic design is up to you, I have used this box, LEDs and switches as they were already in my stock of parts. The die is quite a simple design – with a twist. Inside the unit is a mercury switch. This consists of a small glass tube with two wires at one end and a small amount of mercury. When the mercury rolls over the wires, they are shorted out. Just like a push button when it is pushed, for example:

tiltdemoss

 

We will make use of this switch to start the die “rolling” – to simulate the use of a non-electronic, under-engineered wooden die. For safety, I will be using a mercury switch that is enclosed with plastic:

tiltswitchss

Over the last few years several people have contacted me saying “don’t use mercury switches”. Fair enough, if you don’t want to either, use element-14  part number 540614.

First of all, the circuit is assembled on a breadboard using our Eleven Arduino-compatible board. There is no need to build the complete independent circuit yet, as we just want to test the aspects of the sketch, and try various LEDs out. I have some bright blue ones which match with the blue housing:

bboard1ss

There is a function in the sketch (below) called

which is used to display the numbers 1 to 6. The following video is a demonstration of this:

The sketch is quite simple – you can download it from here. Once the behaviour of the die met my expectation, I used my ZIF-socket programming board to upload the sketch into a nice fresh ATmega328 with bootloader. One could also add a piezo buzzer for sound effects, as described in sketch. This will end up being a birthday present for a young niece, so I have omitted the sound effects.

Next,  time to rebuild the circuit on the breadboard – using the bootrom and not our Eleven. Here is the schematic:

dieschematicss

and the resulting layout:

prototypess

And it works! Things are starting to come together now. As usual I was curious about the current draw, as this helps me determine how long the battery will last. On standby it draws between 10 and 20 milliamps, and between 30 and 40 milliamps when displaying numbers.

By now you probably would like to see it work, so here is the prototype demonstration:

Now it is your turn… from a hardware perspective, we will need the following:

  • IC1 – ATmega328 with Arduino bootloader programmed with the sketch
  • IC2 – LM78L05 voltage regulator – note that with the front facing you, pins are 1-output, 2-GND, 3-input
  • D1-D7 – LEDs of your choosing
  • R1, R9: 10 kilo ohm resistors
  • R2-R8: 560 ohm resistors
  • X1 – 16 MHz resonator – centre pin to ground, outside pins to IC1 pins 9 and 10
  • small piece of protoboard
  • SW1 – on/off button
  • SW2 – mercury tilt switch
  • 9V PP3 battery and snap
  • optional – 28-pin IC socket
  • a nice case, but not too large
  • some thin heatshrink
  • some sponge or insulating foam which has a width and length slightly larger than the protoboard

The ideal housing would be one that fits in the palm of your hand. However, such miniaturisation levels are quite difficult in the home workshop. The biggest problem (literally) was the power supply. The only battery with the voltage and a decent amp-hour rating was the 9V PP3. Alkaline models are usually good for 500 to 625 mAh, and should power the die for about ten hours of continuous use. Furthermore, whilst running the prototype on the breadboard, it would function down to 6 volts, however the LEDs were a little dim – but still perfectly usable. However I managed to squeeze it all in – sans the IC socket.

So if you are like me, and soldering the IC in directly – make sure you are happy with your sketch!

Anyhow, time to start the hardware work of assembly. Using veroboard/protoboard is easy if you plan things out first.

Remember – to fail to plan is to plan to fail

So in this case, I like to get some graph paper and draw out the tracks with a highlighter, such as:

templatess

My diagram shows the tracks as they would be on the rear of the veroboard. With this, using a pencil one can mark out component placement, links, and where to cut tracks if necessary. Those long lines are great for +5V and ground. Etcetera. When you have laid out the parts, go and have a break. Return and check your work, then fire up your iron and go!

Once completed you then have an easy to follow plan to solder along with. Here is the above example after I finished soldering:

after

After the soldering was completed, and the board checked for any shorts or poor-quality joints – it was time to have a clean-up and clear the mess away. Now it was time to stuff the whole lot into the housing… but it would be prudent to test the circuit beforehand. So I soldered in the tilt switch, and the battery snap, connected the battery – and it worked. Notice in the image below the placement of the centre LED – I have used some heatshrink over the legs to totally insulate them, and have it at the centre of the board:

almostdoness

Now to focus on the enclosure. In order to keep the costs down I used a box (and almost everything else) from my existing stock. It turned out to be a little small, but with some creative squeezing everything would fit. The PCB and battery are separated by a thin layer of anti-static foam, to prevent the possibility of the sharp edges of the PCB underside scratching the label of the battery and causing a short.

The final messy task was to drill the holes for the LEDs and the power switch. The switch was easy enough, just knock a small hole in then use a tapered reamer to get the exact size:

switchholess

Then to drill the holes in the lid for the LEDs to poke through. Easily done, just be sure to mark where you want the holes to be before drilling. Furthermore, you need to get the LEDs as far through the holes as possible:

ledsholess

Then the final step before sealing the lot up is to get the power wires soldered to the switch and the battery snap:

beforelidss

When you are putting everything in the box, make sure the tilt switch is tilted so that when the die is at rest, the tilt switch is laying in the off position. Otherwise the die will just merrily repeat forever until you turn it off.

finishedssss1

And of course, an action video:

Once again I hope that this demonstration has shown how easy it is for anyone with some spare time and the knowledge from my Arduino tutorials can create something from scratch.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Posted in arduino, atmega328, dice, games, projects, tutorialComments (4)

Introduction to the Inductor

Hello everyone!

Today we are going to explore the use of the Inductor. This is a continuation from the series of articles on alternating current. An inductor is a component that can resist changes in AC current, and store energy in a magnetic field from a current that passes through it. A changing current (AC) causes a changing magnetic field which induces a voltage that opposes the current produced by the magnetic field. This is known as the inductance.  One could think of an inductor as an AC resistor. But first of all, what is an inductor comprised of?

In simple terms an inductor is a coil of wire, wrapped around a core. The core forms a support for the coil of wire – such as ceramic cores, or in some cases can affect the properties of the magnetic field depending on the chemical composition of the core. These may include cores formed from ferrite (usually zinc and manganese, or zinc and nickel) or powdered iron (which has a tiny air gap allowing the core to store a higher level of magnetic flux (the measure of magnetic field strength)allowing a higher level of DC current to flow through before becoming saturated.

So, the amount of inductance is influenced by several factors – the core material (as above), the size and shape of the core, as well as the number of turns of wire in the coil and its shape. The unit of inductance is the henry (H), however common values are usually in the millihenry (mH) or microhenry (uH) range.

Furthermore, there is an amount of DC resistance due to the properties of the coil wire, however this is usually negligible and kept to a minimum. For example, looking at a data sheet for a typical line of inductors – inductors.pdf – the DC resistance of a 10uH inductor is a maximum of 0.05 ohms. With inductors of higher values, the DC resistance will need to be taken account of. But more about that later.

This is the usual symbol for an inductor in a schematic:

However this may also be used:

And here is a variety of inductors in the flesh:

10microhenryss

radial ferrite core, generally for PCB use, handles around 1.5 amperes

radial leaded, very low resistance, handles around 2.5 amperes

ferrite core, convenient for through-hole PCB

phenolic core

toroidal – handles large currents ~10 amperes depending on model

surface-mount, can still handle around 500 mA

All of the pictured inductors have an inductance of 10 uH. Now let’s examine how inductors work with alternating current. Consider the following circuit:

1

 

Just like capacitors in AC circuits, an inductor has a calculable reactance. The formula for the reactance (X, in ohms) of an inductor is:


where f is the frequency of the AC and L is the value of the inductor in Henries (remember that 1uH is 10 to the power of -6). The formula to calculate the impedance of the above circuit is:

where Z is in ohms. And finally, the formula for AC Vout is

The formula for DC Vout is the usual voltage dividing formula. In this case, as we consider the inductor to not have any resistance, DC Vout = DC Vin.

So, let’s work through an example. Our DC Vin is 12 volts, with a 2V peak to peak AC signal, at a frequency of 20 kHz. The resistor R has a value of 1 kilo ohm, and the inductor L is 10 millihenries (0.01 H). A quick check of the data sheet shows that the 10 mH inductor has a resistance that cannot be ignored – 37.4 ohms. So this must be taken into account when calculating the DC Vout. Therefore we can consider the inductor to be a 37.4 ohm resistor when calculating the DC Vout, which gives us a result of 11.56 volts DC. Substituting the other values gives us a reduced AC signal voltage of 1.24 volts peak to peak.

Another interesting fact is that there is a relationship between AC Vout and the frequency of the AC signal. In the video below, I have used a 10k ohm resistor and a 10 uH inductor in the circuit described above. The frequency counter is measuring the frequency of AC Vin, and the multimeter is measuring the AC Vout:

This is an interesting relationship and demonstrates how an inductor can resist alternating current, depending on the frequency.

Thus ends our introduction to the inductor. We will continue with the inductor in the near future. I hope you understood and can apply what we have discussed today. As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement, you can either leave a comment below or email me – john at tronixstuff dot com.

Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts. Or join our Google Group and post your questions there.

Posted in education, inductor, learning electronics, lesson, test equipment, tutorialComments (0)

Education – the Bipolar Transistor – part two

Hello readers

Today we continue with the second in a series of articles about the bipolar transistor. The first section is here. In this article we look at using the bipolar transistor as an amplifier. That is, change a very small alternating-current signal and make it larger, increasing the amplitude of the signal. Although originally it would seem to be rather simple, perhaps it is not. There are many, many ways to construct a transistor amplifier circuit, but I hope this introduction helps your basic understanding of the process.

When we used the transistor as a switch in part one, we were concerned about the amount of current that flowed between the base and the emitter – that it did not exceed the maximum rating for the particular transistor. When a transistor is allowing the most amount possible of current to flow, it is saturated – the point where the transistor cannot handle any more current. However, to use a transistor as an amplifier we need to bias the transistor so that it is passing current, but not saturated. The procedure of setting the output DC level is known as biasing. The procedure for biasing is outside the scope of this article.

When selecting transistors one needs to take note of the hFE (DC current gain), as variations in this will require a complete recalculation of the values for the bias resistors. Even a common model such as the BC548 is available with hFE ranges between 110~520.

exmple2

one transistor amplifier

Consider the example schematic above. The transistor is not saturated, due to the bias being set by the two 10k ohm resistors, which drops the voltage over the base by around half. In this case with our 6V supply this drops to around 3V. When power is applied, the transistor is biased and allows a small amount of current to flow, but it still has a lot more current-handling capacity. In testing this example, without an input the base current Ib is 0.32 milliamps, and the collector current Ic is 19.9 milliamps . These amounts of current are known as the quiescent current values.

The purpose of the 0.1 uF capacitor is to block DC current and only allow AC current to flow. When the AC current passes through the 0.1 uF capacitor, it is combined with the DC quiescent current running through the base and rides the stronger current out of the emitter. At which point the 100 uF capacitor before the speaker stops the DC current and only allows the AC signal through to the speaker, but amplified. The level of amplification is dependent upon the gain of the transistor, and the amount of base current. Let’s have a look at the behaviour of the current as it passes through the example circuit above:

At the end stage of the video clip we increased the input signal greatly. Did you notice the clipping at the output? This occurs when the voltage is too great for the transistor, and therefore it cannot pass the complete signal through to the emitter. In an audio signal situation, this will cause distortion. That is another reason to check the specification of the transistor against your requirements.

Moving along. You can also connect more than one transistor together to increase the amplification, for example:

exmple2

two-transistor amplifier

The left half of the circuit above should be familiar. The 10uF capacitor at the bottom is to stop the DC current being passed through to the base of the BC548 transistor. The second transistor, the BC558 is a PNP transistor, and amplifies the signal at the collector of the BC548. Finally, the 1uF capacitor blocks the DC current from reaching the output. However in using two or more transistors in such a method, you need to ensure the emitter current rating of the second transistor is much higher, as the gain of two transistors is the product of the individual transistors’ gain.

As stated at the beginning, this is only an introduction. There are literally hundreds of thousands of pages of material written about the use of transistors, so don’t stop here – experiment and do your own research and learning!

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts. Or join our new Google Group.

Posted in amplifier, education, learning electronics, lesson, transistor, tutorialComments (9)

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