Archive | timing

Book – “Arduino Workshop – A Hands-On Introduction with 65 Projects”

Over the last few years I’ve been writing a few Arduino tutorials, and during this time many people have mentioned that I should write a book. And now thanks to the team from No Starch Press this recommendation has morphed into my new book – “Arduino Workshop“:

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Although there are seemingly endless Arduino tutorials and articles on the Internet, Arduino Workshop offers a nicely edited and curated path for the beginner to learn from and have fun. It’s a hands-on introduction to Arduino with 65 projects – from simple LED use right through to RFID, Internet connection, working with cellular communications, and much more.

Each project is explained in detail, explaining how the hardware an Arduino code works together. The reader doesn’t need any expensive tools or workspaces, and all the parts used are available from almost any electronics retailer. Furthermore all of the projects can be finished without soldering, so it’s safe for readers of all ages.

The editing team and myself have worked hard to make the book perfect for those without any electronics or Arduino experience at all, and it makes a great gift for someone to get them started. After working through the 65 projects the reader will have gained enough knowledge and confidence to create many things – and to continue researching on their own. Or if you’ve been enjoying the results of my thousands of hours of work here at tronixstuff, you can show your appreciation by ordering a copy for yourself or as a gift 🙂

You can review the table of contents, index and download a sample chapter from the Arduino Workshop website.

Arduino Workshop is available from No Starch Press in printed or ebook (PDF, Mobi, and ePub) formats. Ebooks are also included with the printed orders so you can get started immediately.

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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, Arduino Workshop, book, books, cellular, clocks, display, distance, ds1307, DS3232, education, EEPROM, freetronics, GPS, graphic, GSM, hardware hacking, I2C, internet, LCD, learning electronics, lesson, no starch press, numeric keypad, part review, product review, projects, RDM630, RDM6300, relay, review, sensor, servo, SMS, time clock, timing, tronixstuff, tutorial, twitter, wireless, xbee13 Comments

Project: Clock Four – Scrolling text clock

Introduction

Time for another instalment in my highly-irregular series of irregular clock projects.  In this we have “Clock Four” – a scrolling text clock. After examining some Freetronics Dot Matrix Displays in the stock, it occurred to me that it would be neat to display the time as it was spoken (or close to it) – and thus this the clock was born. It is a quick project – we give you enough to get going with the hardware and sketch, and then you can take it further to suit your needs.

Hardware

You’ll need three major items – An Arduino Uno-compatible board, a real-time clock circuit or module using either a DS1307 or DS3232 IC, and a Freetronics DMD. You might want an external power supply, but we’ll get to that later on.

The first stage is to fit your real-time clock. If you are unfamiliar with the operation of real-time clock circuits, check out the last section of this tutorial. You can build a RTC circuit onto a protoshield or if you have a Freetronics Eleven, it can all fit in the prototyping space as such:

If you have an RTC module, it will also fit in the same space, then you simply run some wires to the 5V, GND, A4 (for SDA) and A5 (for SCL):

By now I hope you’re thinking “how do you set the time?”. There’s two answers to that question. If you’re using the DS3232 just set it in the sketch (see below) as the accuracy is very good, you only need to upload the sketch with the new time twice a year to cover daylight savings (unless you live in Queensland). Otherwise add a simple user-interface – a couple of buttons could do it, just as we did with Clock Two. Finally you just need to put the hardware on the back of the DMD. There’s plenty of scope to meet your own needs, a simple solution might be to align the control board so you can access the USB socket with ease – and then stick it down with some Sugru:

With regards to powering the clock – you can run ONE DMD from the Arduino, and it runs at a good brightness for indoor use. If you want the DMD to run at full, retina-burning brightness you need to use a separate 5 V 4 A power supply. If you’re using two DMDs – that goes to 8 A, and so on. Simply connect the external power to one DMD’s terminals (connect the second or more DMDs to these terminals):

The Arduino Sketch

You can download the sketch from here. Please use IDE v1.0.1 . The sketch has the usual functions to set and retrieve the time from DS1307/3232 real-time clock ICs, and as usual with all our clocks you can enter the time information into the variables in void setup(), then uncomment setDateDs1307(), upload the sketch, re-comment setDateDs1307, then upload the sketch once more. Repeat that process to re-set the time if you didn’t add any hardware-based user interface.

Once the time is retrieved in void loop(), it is passed to the function createTextTime(). This function creates the text string to display by starting with “It’s “, and then determines which words to follow depending on the current time. Finally the function drawText() converts the string holding the text to display into a character variable which can be passed to the DMD.

And here it is in action:

Conclusion

This was a quick project, however I hope you found it either entertaining or useful – and another random type of clock that’s easy to reproduce or modify yourself. We’re already working on another one which is completely different, so stay tuned.

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, clocks, dmd, ds1307, DS3232, freetronics, learning electronics, LED matrix, microcontrollers, projects, scrolling, time clock, timing, tutorial10 Comments

Project: Clock One

Let‘s make a huge analogue and digital clock using a dot-matrix display. 

Updated 18/03/2013

For some strange reason I have a fascination with various types of electronic clocks (which explains this article). Therefore this project will be the start of an irregular series of clock projects whose goal will be easy to follow and produce interesting results. Our “Clock One” will use a Freetronics Dot Matrix Display board as reviewed previously. Here is an example of an operating Clock One:

As you can see, on the left half of the board we have a representation of an analogue clock. Considering we only have sixteen rows of sixteen LEDs, it isn’t too bad at all. The seconds are illuminated by sixty pixels that circumnavigate the square clock throughout the minute. On the right we display the first two letters of the day of the week, and below this the date. In the example image above, the time is 6:08. We omitted the month – if you don’t know what month it is you have larger problems.

Hardware

To make this happen you will need:

  • Freetronics Dot Matrix Display board;
  • If you want the run the display at full brightness (ouch!) you will need a 5V 2.8A power supply – however our example is running without the external supply and is pretty strong
  • An Arduino board of some sort, an Uno or Eleven is a good start
  • A Maxim DS1307 real-time clock IC circuit. How to build this is explained here. If you have a Freetronics board, you can add this circuit directly onto the board!

Software

Planning the clock was quite simple. As we can only draw lines, individual pixels, and strings of text or individual characters, some planning was required in order to control the display board. A simple method is to use some graph paper and note down where you want things and the coordinates for each pixel of interest, for example:

Using the plan you can determine where you want things to go, and then the coordinates for pixels, positions of lines and so on. The operation for this clock is as follows:

  • display the day of week
  • display the date
  • draw the hour hand
  • draw the minute hand
  • then turn on each pixel representing the seconds
  • after the 59th second, turn off the pixels on the left-hand side of the display (to wipe the clock face)

There isn’t a need to wipe the right hand side of the display, as the characters have a ‘clear’ background which takes care of this when updated. At this point you can download the Arduino sketch from here. Note that the sketch was written to get the job done and ease of reading and therefore not what some people would call efficient. Some assumed knowledge is required – to catch up on the use of the display, see here; and for DS1307 real-time clock ICs, see here.

The sketch uses the popular method of reading and writing time data to the DS1307 using functions setDateDs1307 and getDateDs1307. You can initally set the time within void setup() – after uploading the sketch, comment out the setDateDs1307 line and upload the sketch again, otherwise every time the board resets or has a power outage the time will revert to the originally-set point.

Each display function is individual and uses many switch…case statements to determine which line or pixel to draw. This was done again to draw the characters on the right due to function limitations with the display library. But again it works, so I’m satisfied with it. You are always free to download and modify the code yourself.  Moving forward, here is a short video clip of the Clock One in action:

For more information about the display used, please visit the Freetronics product pageDisclaimer – The display module used in this article is a promotional consideration made available by Freetronics.

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, clocks, dmd, ds1307, DS3232, freetronics, LED matrix, timing, tutorial16 Comments

Tutorial: Arduino timing methods with millis()

This is chapter thirty-seven of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – in what feels like an endless series of articles on the Arduino universe. The first chapter is here, the complete series is detailed here. Any files from tutorials will be found here.

[Updated 20/01/2013]

In this article we introduce the millis(); function and put it to use to create various timing examples.

Millis? Nothing to do with lip-syncers… hopefully you recognised milli as being the numerical prefix for one-thousandths; that is multiplying a unit of measure by 0.001 (or ten to the power of negative 3). Interestingly our Arduino systems will count the number of milliseconds (thousands of a second) from the start of a sketch running until the count reaches the maximum number capable of being stored in the variable type unsigned long (a 32-bit [four byte] integer – that ranges from zero to (2^32)-1.

(2^32)-1, or 4294967295 milliseconds converts to 49.71027-odd days. The counter resets when the Arduino is reset, it reaches the maximum value or a new sketch is uploaded. To get the value of the counter at a particular juncture, just call the function – for example:

Where start is an unsigned long variable. Here is a very simple example to show you millis() in action:

The sketch stores the current millis count in start, then waits one second, then stores the value of millis again in finished. Finally it calculates the elapsed time of the delay.  In the following screen dump of the serial monitor, you can see that the duration was not always exactly 1000 milliseconds:

To put it simply, the millis function makes use of an internal counter within the ATmega microcontroller at the heart of your Arduino. This counter increments every clock cycle – which happens (in standard Arduino and compatibles) at a clock speed of 16 Mhz. This speed is controlled by the crystal on the Arduino board (the silver thing with T16.000 stamped on it):

Crystal accuracy can vary depending on external temperature, and the tolerance of the crystal itself. This in turn will affect the accuracy of your millis result. Anecdotal experience has reported the drift in timing accuracy can be around three or four seconds per twenty-four hour period. If you are using a board or your own version that is using a ceramic resonator instead of a crystal, note that they are not as accurate and will introduce the possibility of higher drift levels. If you need a much higher level of timing accuracy, consider specific timer ICs such as the Maxim DS3232.

Now we can make use of the millis  for various timing functions. As demonstrated in the previous example sketch, we can calculate elapsed time. To take this idea forward, let’s make a simple stopwatch. Doing so can be as simple or as complex as necessary, but for this case we will veer towards simple. On the hardware perspective, we will have two buttons – Start and Stop – with the 10k ohm pull-down resistors connected to digital pins 2 and 3 respectively.

When the user presses start the sketch will note the value for millis – then after stop is pressed, the sketch will again note the value for millis, calculate and display the elapsed time. The user can then press start to repeat the process, or stop for updated data. Here is the sketch:

The calls to delay() are used to debounce the switches – these are optional and their use will depend on your hardware. Below is an example of the sketch’s serial monitor output – the stopwatch has started, and then button two pressed six times across periods of time:

If you had a sensor at the start and end of a fixed distance, speed could be calculated: speed = distance ÷ time.

You can also make a speedometer for a wheeled form of motion, for example a bicycle. At the present time I do not have a bicycle to mess about with, however we can describe the process to do so – it is quite simple. (Disclaimer – do so at your own risk etc.)  First of all, let’s review the necessary maths. You will need to know the circumference of the wheel. Hardware – you will need a sensor. For example – a reed switch and magnet. Consider the reed switch to be a normally-open button, and connect as usual with a 10k ohm pull-down resistor. Others may use a hall-effect sensor – each to their own). Remember from maths class:

(image licence)

To calculate the circumference – use the formula:

circumference = 2πr 

where r is the radius of the circle. Now that you have the wheel circumference, this value can be considered as our ‘fixed distance’, and therefore the speed can be calculated by measuring the elapsed time between of a full rotation.

Your sensor – once fitted – should act in the same method as a normally-open button that is pushed every rotation. Our sketch will measure the time elapsed between every pulse from the sensor. To do this, our example will have the sensor output connected to digital pin 2 – as it will trigger an interrupt to calculate the speed. (Interrupts? See chapter three). The sketch will otherwise be displaying the speed on a normal I2C-interface LCD module. The I2C interface is suggested as this requires only 4 wires from the Arduino board to the LCD – the less wires the better.

Here is the sketch for your perusal:

There isn’t that much going on – every time the wheel completes one revolution the signal from the sensor will go from low to high – triggering an interrupt which calls the function speedCalc(). This takes a reading of millis() and then calculates the difference between the current reading and the previous reading – this value becomes the time to cover the distance (which is the circumference of the wheel relative to the sensor – stored in

and is measured in metres). It finally calculates the speed in km/h and MPH. Between interrupts the sketch displays the updated speed data on the LCD as well as the raw time value for each revolution for curiosity’s sake. In real life I don’t think anyone would mount an LCD on a bicycle, perhaps an LED display would be more relevant.

In the meanwhile, you can see how this example works in the following short video clip. Instead of a bike wheel and reed switch/magnet combination, I have connected the square-wave output from a function generator to the interrupt pin to simulate the pulses from the sensor, so you can get an idea of how it works:

That just about sums up the use of millis() for the time being. There is also the micros(); function which counts microseconds. So there you have it – another practical function that can allow more problems to be solved via the world of Arduino. As always, now it is up to you and your imagination to find something to control or get up to other shenanigans.

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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, education, learning electronics, lesson, microcontrollers, millis, speedometer, stopwatch, timing, tutorial18 Comments

Let’s make an Arduino real time clock shield

[Updated 15/03/2013]

Today we are going to make a real time clock Arduino shield. Doing so will give you a simple way of adding … real time capability to your projects such as time, date, alarms and so on. We will use the inexpensive Maxim DS1307 real-time clock IC.

First of all, we need create our circuit diagram. Thankfully the Maxim DS1307 data sheet [pdf] has this basics laid out on page one. From examining a DS1307 board used in the past, the pull-up resistors used were 10k ohm metal films, so I’m sticking with that value. The crystal to use is 32.768 kHz, and thankfully Maxim have written about that as well in their application notes [pdf], even specifying which model to use. Phew!

So here is the circuit diagram we will follow:

ds1307shield2

Which gives us the following shopping list:

  • One arduino protoshield pack. I like the yellow ones from Freetronics
  • X1 – 32.768 kHz crystal – Citizen America part CFS206. You should probably order a few of these, I broke my first one very quickly…
  • IC1 – Maxim DS1307 real time clock IC
  • 8-pin IC socket
  • CR2032 3v battery
  • CR2032 PCB mount socket
  • R1~R3 – 10k ohm metal film resistors
  • C1 – 0.1 uF ceramic capacitor

And here are our parts, ready for action:

partssmall1

The first thing to do is create the circuit on a solderless breadboard. It is much easier to troubleshoot possible issues before soldering the circuit together. Here is the messy test:

ds1307breadboardsmall

Messy or not, it worked. You can use the following sketch to test the circuit is working. The next step is to consider the component placement and wiring for the protoshield. Please note that my board will most likely be different to yours, so please follow the schematic and not my board positioning. Try not to rush this step, and triple-check your layout against the schematic. As my protoshield has a green and red LED as well, I have wired the square-wave output to the green LED. You can never have too many blinking lights…

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At this point I celebrated the union of tea and a biscuit. After returning to the desk, I checked the layout once more, and planned the solder bridges. All set – it was time to solder up. If you have the battery in the holder for some reason, you should remove it now, as they do not like getting warm. Furthermore, that crystal is very fragile, so please solder it in quickly.

And here we are – all soldering done except for the header sockets. At this point I used the continuity function of the multimeter to check the solder joints and make sure nothing was wrong with the circuit:

topsoldersmall

 

bottomsoldersmall

Final checks passed, so on with the headers. Just a side note – always make sure you have enough consumables, the right tools, etc., before you start a project. This is how much solder I had left afterwards…

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Moving on … in with the battery and the DS1307 –  we’re done!

finishedasmall

finishedbsmall

It is now time for the moment of truth – to insert the USB cable and re-run the sketch… and it worked! The blinking LED was too bright for me, so I de-soldered the wire. If you are making a shield, congratulations to you if yours worked as well. Note that if you are using this shield, you cannot use analog pins 4 and 5 – they are being used as the I2C bus.

So there we have it. Another useful shield, and proof that the Arduino system makes learning easy and fun. High resolution photos are 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 arduino, ds1307, education, projects, time clock, timing, tutorial2 Comments


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