Tag Archive | "SOIC"

Review – Schmartboard SMT Boards

In this article we review a couple of SMT prototyping boards from Schmartboard.

Introduction

Sooner or later you’ll need to use a surface-mount technology component. Just like taxes and myki* not working, it’s inevitable. When the time comes you usually have a few options – make your own PCB, then bake it in an oven or skillet pan; get the part on a demo board from the manufacturer (expensive); try and hand-solder it yourself using dead-bug wiring or try to mash it into a piece of strip board; or find someone else to do it. Thanks to the people at Schmartboard you now have another option which might cost a few dollars more but guarantees a result. Although they have boards for almost everything imaginable, we’ll look at two of them – one for QFP packages and their Arduino shield that has SOIC and SOP23-6 areas.

boards

QFP 32-80 pin board

In our first example we’ll see how easy it is to prototype with QFP package ICs. An example of this is the Atmel ATmega328 microcontroller found on various Arduino-compatible products, for example:

atmega

Although our example has 32 pins, the board can handle up to 80-pin devices. You simply place the IC on the Schmartboard, which holds the IC in nicely due to the grooved tracks for the pins:

atmegabefore

The tracks are what makes the Schmartboard EZ series so great – they help hold the part in, and contain the required amount of solder. I believe this design is unique to Schmartboard and when you look in their catalogue, select the “EZ” series for this technology. Moving forward, you just need some water-soluble flux:

fluxpen

then tack down the part, apply flux to the side you’re going to solder – then slowly push the tip of your soldering iron (set to around 750 degrees F) down the groove to the pin. For example:

Then repeat for the three other sides. That’s it. If your part has an exposed pad on the bottom, there’s a hole in the centre of the Schmartboad that you can solder into as well:

qfpheat

After soldering I really couldn’t believe it worked, so probed out the pins to the breakout pads on the Schmartboard to test for shorts or breaks – however it tested perfectly. The only caveat is that your soldering iron tip needs to be the same or smaller pitch than the the part you’re using, otherwise you could cause a solder bridge. And use flux!  You need the flux. After soldering you can easily connect the board to the rest of your project or build around it.

Schmartboard Arduino shield

There’s also a range of Arduino shields with various SMT breakout areas, and we have the version with 1.27mm pitch SOIC and a SOT23-6 footprint. SOIC? For example:

soicic

This is the AD5204 four-channel digital potentiometer we used in the SPI tutorial. It sits nicely in the shield and can be easily soldered onto the board. Don’t forget the flux! Although the SMT areas have the EZ-technology, I still added a little solder of my own – with satisfactory results:

The SOT23-6 also fits well, with plenty of space for soldering it in. SOT23? Example – the ADS1110 16-bit ADC which will be the subject of a future tutorial:

ads1110

Working with these tiny components is also feasible but requires a finer iron tip and a steady hand.

sot236

Once the SMT component(s) have been fitted, you can easily trace out the matching through-hole pads for further connections. The shield matches the Arduino R3 standards and includes stacking header sockets, two LEDs for general use, space and parts for an RC reset circuit, and pads to add pull-up resistors for the I2C bus:

otherparts

Finally there’s also three 0805-sized parts and footprints for some practice or use. It’s a very well though-out shield and should prove useful. You can also order a bare PCB if you already have stacking headers to save money.

Conclusion

If you’re in a hurry to prototype with SMT parts, instead of mucking about – get a Schmartboard. They’re easy to use and work well.  Full-sized 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.

The boards used in this article were a promotional consideration supplied by Schmartboard.

*myki

Posted in arduino, product review, review, safety, schmartboard, SMD, SMT, soic, soldering, sot-23, tqfp, tronixstuff, tutorialComments (2)

Experimenting with Surface-Mount Component Prototyping

Experimenting with hand-soldering SMT components.

Updated 18/03/2013

Now and again I have looked at SMT (surface-mount technology) components and thought to myself “I should try that one day”. But not wanting to fork out for a toaster oven and a bunch of special tools I did it on the cheap – so in this article you can follow along and see the results. Recently I ordered some ElecFreaks SOIC Arduino Mega-style protoshields which apart from being a normal double-sided protoshield, also have a SOIC SMT pad as shown below:

First up I soldered in two SOIC format ICs – a 555 and a 4017:

These were not that difficult – you need a steady hand, a clean soldering iron tip and some blu-tac. To start, stick down the IC as such:

… then you can … very carefully … hand-solder in a few legs, remove the blu tac and take care of the rest …

The 4017 went in easily as well…

…however it can be easier to flood the pins with solder, then use solder-wick to soak up the excess – which in theory will remove the bridges between pins caused by the excess solder. And some PCB cleaner to get rid of the excess flux is a good idea as well.

Now to some smaller components – some LEDs and a resistor. These were 0805 package types, which measure 2.0 × 1.3 mm – for example a resistor:

The LEDs were also the same size. Unlike normal LEDs, determining the anode and cathode can be difficult – however my examples had a small arrow determining current flow (anode to cathode) on the bottom:

Another way is to use the continuity function of a multimeter – if their output voltage is less than the rating of the LED, you can probe it to determine the pins. When it glows, the positive lead is the anode. Handling such small components requires the use of anti-magnetic tweezers – highly recommended…

… and make holding down the components with one hand whilst soldering with the other much, much easier. Unlike normal veroboard, protoshield or other prototyping PCBs the protoshield’s holes are surrounded with a “clover” style of solder pad, for example:

These solder pads can make hand-soldering SMT parts a little easier. After some experimenting, I found the easiest way was to first flood the hold with solder:

… then hold down the component with the tweezers with one hand while heating the solder with the other – then moving and holding one end of the component into the molten solder:

The first time (above) was a little messy, but one improves with practice. The clover-style of the solder pads makes it easy to connect two components, for example:

With some practice the procedure can become quite manageable:

As the protoshields are double-sided you can make connections between components on the other side to keep things neat for observers. To complete the experiment the six LEDs were wired underneath (except for one) to matching Arduino Mega digital output pins, and a simple demonstration sketch used to illuminate the LEDs, as shown below:

For one-off or very low-volume SMD work these shields from elecfreaks are quite useful. You will need a steady hand and quite a lot of patience, but if the need calls it would be handy to have some of these boards around just in case. For a more involved and professional method of working with SMT, check out this guide by Jon Oxer.

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 555, education, elecfreaks, learning electronics, SMD, soldering, tutorialComments (6)

Kit Reviews: Snootlab Power ScrewShield and I2C Power Protoshield

Hello Readers

In this article we will examine the first two products from a bundle sent for review by Snootlab, a Toulouse, France-based company that in their own words:

… designs and develops electronic products with an Open Hardware and Open Source approach. We are particularly specialized in the design of new shields for Arduino. The products we create are licensed under CC BY-SA v3.0 (as shown in documents associated with each of our creations). In accordance with the principles of the definition of Open Source Hardware (OSHW), we have signed it the 10th February 2011. We wish to contribute to the development of the ecosystem of “do it yourself” through original designs of products, uses and events.

Furthermore, all of their products are RoHS compliant and as part of the Open Hardware commitment, all the design files are available from the Snootlab website. First, let’s examine the Power Screwshield kit. This is a feature-laden prototyping shield suitable for Arduino Uno and compatible series boards. It can be used with the Mega, however not all of the I/O pins will be available.

Apart from obvious use as a prototyping shield, there are also three other useful features:

  • space for a 16-pin SOIC SMD part in the prototyping area;
  • a full line of screw terminals that connect to all the shield pin connections (in a similar way to the Wingshield Screwshield);
  • and a socket to allow power to be sourced from a standard computer ATX power supply, which brings 5V and 12V DC to the shield. I have never seen this implemented on a shield in the past – a very novel and useful idea.
If you are unfamiliar with the ATX power supply options, consider this image of the tronixstuff bench PC’s internals:
ldo3ss
The connector we would use is the one with the four round pins in a single row. In recent times using PC power supplies as bench power supply units has become quite common, so the designers at Snootlab have taken advantage of this in a very clever way by allowing their Power ScrewShield to use these power supplies. Assembly of the shield is simple and well documented. Although it is self-explanatory, you can download an illustrated guide from here. The kit is packaged in a reusable ESD bag:

bagss

Assembly of the shield is simple and well documented. Although it is self-explanatory, you can download an illustrated guide from here. The kit is packaged in a reusable ESD bag:

… which contains all the necessary parts:

partsss

… and a very high quality PCB:

pcbss

The PCB thickness is over 1mm, and as you can see from the image above the silk-screening describes all the areas of the PCB in a detailed manner. Note that this shield is much larger than a standard Arduino shield – this becomes obvious when compared with a standard prototyping shield:

pcbcompss

Assembly was very smooth and quick. There are a couple of things to watch out for, for example you need to slide the terminal blocks together so that they are flush on the sides, such as:

blocks

… if you want to enable the 12V DC rail from the ATX power lead, short out the jumper SJ1 with a blob of solder:

enable12vss

… when soldering the PC power connector, be sure to make the clamp bracket flush with the socket, for example:

atxss

… and finally, to enable use of the shield’s LED, you need to cut the track in this area on the underside of the PCB:

Although at first the introduction of another Arduino prototyping shield may not have seemed that interesting – this version from Snootlab really goes all out to cover almost every possible need in a shield all at the same time. Sure, it is a lot larger – but none of the board space is wasted – and those terminal blocks would be very hand for making some more permanent-style prototypes with lots of external wiring.  And the ability to accept power from a PC ATX-style power supply unit is certainly original and possibly very useful depending on your application. So if you need to create something that needs a lot of power, a lot of prototyping space, and a lot of wiring – this is the protoshield for you.

For the second half of the review we have the Snootlab I2C Power Protoshield. This is another example of an Arduino prototyping shield with some interesting twists. Apart from employing the same PC power connector as used with the Power ScrewShield, this shield is designed for hard-core I2C-bus enthusiasts. (What’s I2C? Check my tutorials). This is due to the 10-pin HE connector on the edge of the board – it contains pins for SCL, SDA, 3.3V, 5V and GND. With this you could use you own cable connections to daisy-chain other devices communicating via the I2C bus. Again, the shield is a kit and assembly was simple.

Like other Snootlab products, the kit arrives in a reusable ESD bag:

bag

… with a high-quality thick PCB that has a very detailed silk-screen layer:

pcb

… and all the required parts are included:

parts1

When soldering in the shield connectors, using another shield as a jig can save time:

headers

And we’re finished:

finished

One could also mount a small solderless breadboad on the I2C Power Protoshield:

finishedwithbreadboard

One great feature is the inclusion of an NCP1117DT33 3.3V 1A voltage regulator. Using this you can source 3.3 volts at up to one amp of current (only) when using the PC power supply connection. This is a great idea, as in the past it can be too easy to accidentally burn out the FTDI chip on an Arduino Duemilanove by drawing too much current from the 3.3V pin. The use of the external 3.3V supply is controlled by a jumper on the header pins here:

intext3v3

Finally, in the image above you can see the area for external I2C pull-up resistors. Generally with our Arduino the internal pull-up resistors in the microcontroller are adequate, however with many I2C devices in use (e.g. eight 24LC512 EEPROMS!) external pull-ups are required.

After examining the two shields I am impressed with the quality of the components and PCBs, as well as the interesting features described in the review. Theyare certainly unique and very much useful if required, especially the PC power supply connections. Support is available on the Snootlab website, and there is also a customer forum in French (use Google Translate). However the people at Snootlab converse in excellent English and have been easy to contact via email if you have any questions. Stay tuned for more interesting Snootlab product reviews.

Snootlab products including the I2C Power Protoshield and the Power ScrewShield are available directly from their website.

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 on twitterfacebook, or join our Google Group.

[Disclaimer – the products reviewed in this article are promotional considerations made available by Snootlab]

Posted in arduino, kit review, microcontrollers, snootlabComments (13)

Tutorial: Arduino and the I2C bus – Part One

This is part one of several tutorials on how to use the I2C bus with Arduino, and chapter twenty 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 28/11/2014]

In this first of several tutorials we are going to investigate the I2C data bus, and how we can control devices using it with our Arduino systems. The I2C bus can be a complex interface to master, so I will do my best to simplify it for you. In this article we will learn the necessary theory, and then apply it by controlling a variety of devices. Furthermore it would be in your interest to have an understanding of the binary, binary-coded decimal and hexadecimal number systems.

But first of all, what is it?

I2C is an acronym for “Inter-Integrated Circuit”. In the late 1970s, Philips’ semiconductor division (now NXP) saw the need for simplifying and standardising the data lines that travel between various integrated circuits in their products. Their solution was the I2C bus. This reduced the number of wires to two (SDA – data, and SCL – clock). Here is a nice introductory video from NXP:

Why would we want to use I2C devices?

As there are literally thousands of components that use the I2C interface! And our Arduino boards can control them all. There are many applications, such a real-time clocks, digital potentiometers, temperature sensors, digital compasses, memory chips, FM radio circuits, I/O expanders, LCD controllers, amplifiers, and so on. And you can have more than one on the bus at any time, in fact the maximum number of I2C devices used at any one time is 112.

From a hardware perspective, the wiring is very easy. Those of you with an Arduino Uno or 100% compatible board, you will be using pins A4 for SDA (data) and A5 for SCL (clock):

arduino-uno-i2c-pin

If you are using an Arduino Mega, SDA is pin 20 and SCL is 21, so note that shields with I2C need to be specifically for the Mega. If you have another type of board, check your data sheet or try the Arduino team’s hardware website.  And finally, if you are using a bare DIP ATmega328-PU microcontroller, you will use pins 27 for SDA and 28 for SCL. The bus wiring is simple:

nxpi2cbussmall

If you are only using one I2C device, the pull-up resistors are (normally) not required, as the ATmega328 microcontroller in our Arduino has them built-in.  However if you are running a string of devices, use two 10 kilo ohm resistors. Like anything, some testing on a breadboard or prototype circuit will determine their necessity. Sometimes you may see in a particular device’s data sheet the use of different value pull-up resistors – for example 4.7k ohm. If so, heed that advice. The maximum length of an I2C bus is around one metre, and is a function of the capacitance of the bus. This distance can be extended with the use of a special IC, which we will examine during the next I2C chapter.

Each device can be connected to the bus in any order, and devices can be masters or slaves. In our Arduino situation, the board is the master and the devices on the I2C bus are the slaves. We can write data to a device, or read data from a device. By now you should be thinking “how do we differentiate each device on the bus?”… Each device has a unique address. We use that address in the functions described later on to direct our read or write requests to the correct device. It is possible to use two devices with identical addresses on an I2C bus, but that will be discussed in a later article.

As like most devices, we make use of an Arduino library, in this case <wire.h>. Then use the function Wire.begin(); inside of void setup() and we’re ready to go.

Sending data from our Arduino to the I2C devices requires two things: the unique device address (we need this in hexadecimal) and at least one byte of data to send. For example, the address of the part in example 20.1 (below) is 00101111 (binary) which is 0X2F in hexadecimal. Then we want to set the wiper value, which is a value between 0 and 127, or 0x00 and 0x7F in hexadecimal. So to set the wiper to zero, we would use the following three functions:

This sends the device address down the SDA (data) line of the bus. It travels along the bus, and “notifies” the matching device that it has some data coming…

This sends the byte of data to the device – into the device register (or memory of sorts), which is waiting for it with open arms. Any other devices on the bus will ignore this. Note that you can only perform one I2C operation at a time! Then when we have finished sending data to the device, we “end transmission”. This tells the device that we’re finished, and frees up the I2C bus for the next operation:

Some devices may have more than one register, and require more bytes of data in each transmission. For example, the DS1307 real-time clock IC has eight registers to store timing data, each requiring eight bits of data (one byte):

ds1307registers

However with the DS1307  – the entire lot need to be rewritten every time. So in this case we would use eight wire.send(); functions every time. Each device will interpret the byte of data sent to it, so you need the data sheet for your device to understand how to use it.

Receiving data from an I2C device into our Arduino requires two things: the unique device address (we need this in hexadecimal) and the number of bytes of data to accept from the device. Receiving data at this point is a two stage process. If you review the table above from the DS1307 data sheet, note that there is eight registers, or bytes of data in there. The first thing we need to do is have the I2C device start reading from the first register, which is done by sending a zero to the device:

Now the I2C device will send data from the first register when requested. We now need to ask the device for the data, and how many bytes we want. For example, if a device held three bytes of data, we would ask for three, and store each byte in its own variable (for example, we have three variables of type byte: a, b, and c. The first function to execute is:

Which tells the device to send three bytes of data back to the Arduino. We then immediately follow this with:

We do not need to use Wire.endTransmission() when reading data. Now that the requested data is in their respective variables, you can treat them like any ordinary byte variable. For a more detailed explanation of the I2C bus, read this explanatory document by NXP. Now let’s use our I2C knowledge by controlling a range of devices…

The Microchip MCP4018T digital linear potentiometer. The value of this model is 10 kilo ohms. Inside this tiny, tiny SMD part is a resistor array consisting of 127 elements and a wiper that we control by sending a value of between 0 and 127 (in hexadecimal) down the I2C bus. This is a volatile digital potentiometer, it forgets the wiper position when the power is removed. However naturally there is a compromise with using such a small part, it is only rated for 2.5 milliamps – but used in conjunction with op amps and so on. For more information, please consult the data sheet. As this is an SMD part, for breadboard prototyping purposes it needed to be mounted on a breakout board. Here it is in raw form:

mcp4018raw

Above the IC is a breakout board. Consider that the graph paper is 5mm square! It is the incorrect size, but all I have. However soldering was bearable. Put a drop of solder on one pad of the breakout board, then hold the IC with tweezers in one hand, and reheat the solder with the other hand – then push the IC into place. A few more tiny blobs of solder over the remaining pins, and remove the excess with solder wick. Well … it worked for me:

mcp4018cooked

Our example schematic is as follows:

mcp4018sch

As you can see, the part is simple to use, your signal enters pin 6 and the result of the voltage division is found on pin 5. Please note that this is not a replacement for a typical mechanical potentiometer, we can’t just hook this up as a volume or motor-speed control! Again, please read the data sheet.

Control is very simple, we only need to send one byte of data down, the hexadecimal reference point for the wiper, e.g.:

Here is a quick demonstration that moves the wiper across all points:

 and a video demonstration:


Now we will read some data from an I2C device. Our test subject is the ST Microelectronics CN75 temperature sensor. Again, we have another SMD component, but the CN75 is the next stage larger than the part from example 20.1. Thankfully this makes the soldering process much easier, however still requiring some delicate handiwork:

cn75solder1

First, a small blob of solder, then slide the IC into it. Once that has cooled, you can complete the rest and solder the header pins into the breakout board:

cn75solder2ss

Our example schematic is as follows:

cn75schem

Pins 5, 6 and 7 determine the final three bits of the device address – in this case they are all set to GND, which sets the address to 1001000. This allows you to use multiple sensors on the same bus. Pin 3 is not used for basic temperature use, however it is an output for the thermostat functions, which we will examine in the next chapter.

As a thermometer it can return temperatures down to the nearest half of a degree Celsius. Although that may not be accurate enough, it was designed for automotive and thermostat use. For more details please read the data sheet. The CN75 stores the temperature data in two bytes, let’s call them A and B. So we use

with the second parameter as 2, as we want two bytes of data. Which we then store using the following functions:

where *a and *b are variables of the type byte. And as always, there is a twist to decoding the temperature from these bytes. Here are two example pieces of sample data:

The bits in each byte note particular values… the most significant bit (leftmost) of byte A determines whether it is below or above zero degrees – 1 for below zero. The remaining seven bits are the binary representation of the integer part of the temperature; if it is below zero, we subtract 128 from the value of the whole byte and multiply by -1. The most significant bit of byte B determines the fraction, either zero or half a degree. So as you will see in the following example sketch, there is some decision making done in showCN75data():

And here is the result from the serial monitor:

Now that we know how to read and write data to devices on the I2C bus – here is an example of doing both, with a very popular device – the Maxim DS1307 real-time clock IC. Before moving on, consider reading their good data sheet.

ds1307small

Furthermore, it also has a programmable square-wave generator. Connection and use is quite simple:

ds1307schem

However some external components are required: a 32.768 kHz crystal, a 3V battery for time retention when the power is off, and a 10k ohm pullup resistor is required if using as a square-wave generator, and 10k ohm pull-up resistors on the SCL and SDA lines. You can use the SQW and timing simultaneously. If we have a more detailed look at the register map for the DS1307:

ds1307registers

We see that the first seven registers are for timing data, the eighth is the square-wave control, and then another eight RAM registers. In this chapter we will look at the first eight only. Hopefully you have noticed that various time parameters are represented by less than eight bits of data – the DS1307 uses binary-coded decimal. But don’t panic, we have some functions to do the conversions for us.

However, in general  – remember that each bit in each register can only be zero or one – so how do we represent a register’s contents in hexadecimal? First, we need to find the binary representation, then convert that to hexadecimal. So, using the third register of the DS1307 as an example, and a time of 12:34 pm – we will read from left to right. Bit 7 is unused, so it is 0. Bit 6 determines whether the time kept is 12- or 24-hour time. So we’ll choose 1 for 12-hour time. Bit 5 (when bit 6 is 0) is the AM/PM indicator – choose 1 for PM. Bit 4 represents the left-most digit of the time, that is the 1 in 12:34 pm. So we’ll choose 1. Bits 3 to 0 represent the BCD version of 2 which is 0010.

So to store 12pm as hours we need to write 00110010 as hexadecimal into the hours register – which is 0x32. Reading data from the DS1307 should be easy for you now, reset the register pointed, then request seven bytes of data and receive them into seven variables. The device address is 0x68.  For example:

At which point the time data will need to be converted to decimal numbers, which we will take care of in the example sketch later. Setting the time, or controlling the square-wave output is another long operation – you need to write seven variables to set the time or eight to change the square-wave output. For example, the time:

The decToBcd is a function defined in our example to convert the decimal numbers to BCD suitable for the DS1307.

You can also address each register individually. We will demonstrate doing this with an explanation of how to control the DS1037’s in built square-wave generator:

Here is the SQW output in action – we measure the frequency using my very old Tek CFC-250:

For further DS1307 examples, I will not repeat myself and instead direct you to the list of many tronixstuff articles that make use of the DS1307.

So there you have it – hopefully an easy to understand introduction to the world of the I2C bus and how to control the devices within. Part two of the I2C tutorial has now been published, as well as an article about the NXP SAA1064 LED display driver IC and the Microchip MC23017 16-bit port expander IC.

 

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 fourth 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.

Posted in arduino, CN75, ds1307, education, I2C, learning electronics, lesson, MCP4018T, microcontrollers, tutorialComments (22)


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