February 2011 Competition

Hello readers

The February 2011 competition has now closed. Thank you to all those who entered, and the results have now been posted.

Time for another competition – and the best one yet! To enter, find the five questions that are spread across the articles published in tronixstuff.com in February. When you have answers to all five questions, email your answers to competition at tronixstuff dot com with “February″ in the subject line. Then in the first week of March, I will compile a list of people with the correct answers, and randomly select two winners. Now for the prizes – brought to you this month by the great people from Freetronics.

First Prize

One brand-new, hot off the pick-and-place Freetronics “Eleven” 100% Arduino Uno-compatible board

The “Eleven” is just like an Arduino Uno – but better!
It is based on the existing Arduino Uno but with improvements and updates for ease of use, cost and getting started.
It’s 100% Arduino compatible. Also included in the package are a USB cable, and our Getting Started guide sheet.

As well as the standard Arduino Uno features found here, the Eleven has the following improvements and updates:

Prototyping area
For those projects where you don’t need the extra size or expense of a shield, the Eleven has its own standard prototyping area taking up a quarter of the board. Great for quick sensor and IC projects. There’s extra power pads underneath for neat connections.

LEDs visible on the edge
Wondered what your Arduino was doing? We’ve carefully placed a nice blue Power LED, plus colour coded RX, TX and D13 LEDs on the right edge of the board so you can see what’s going on.

Dual crystals
We’ve provided proper crystals for both the primary MCU and the communications MCU, rather than using a ceramic resonator.

Mini-USB Connector
No more short circuits of the large USB connector against your shields. Our standard Mini-USB connector is firmly mounted and we’ve included a cable too.

Overlay guide where you need it
When you’re soldering your project, it’s good to know what you’re connecting to! All of our boards and shields have a thorough pinout and guide printed on the bottom as well as the top, so when you’re soldering underneath there’s no need to flip the board over constantly.

Top spec MCU
Every Eleven has the higher specification ATmega328P Microcontroller.

D13 pin works for everything
The digital I/O pin 13 functionality has been fixed, the D13 indicator LED no longer loads up this pin when you use it as an input.

Mounting holes, power and X3 pads
We’ve included a fourth mounting hole in the bottom left, there’s no more wobbly board troubles if you’re fitting it to a case.
Helpful markings for the Power Jack size, polarity and voltage are right there on the board when you need them. Auto-power switching and self-resetting fuse protection are standard.
Really need to program the bootloader into an MCU? Not usually required, but we’ve included a DIP socket and the X3 programming pads for it.

It’s all in the same place
The power jack, headers and ICSP are all in exactly the same location as Arduino standard boards. The Eleven is perfectly compatible with all Arduino shields, projects and sketches.

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What’s in the box?

• Freetronics Eleven board
• A Mini-USB cable so you don’t need to purchase one separately!
• Our carefully written Getting Started guide

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Second Prize

One brand-new, Freetronics “KitTen” 100% Arduino Duemilanove-compatible board kit

As seen in the recent kit review, the lucky winner will enjoy making a great Arduino-compatible board that is easy and fun. More about the KitTen:

The KitTen is a simplified version of our TwentyTen (“Duemiladieci”) Arduino-compatible board, supplied as a kit using through-hole parts for easy assembly.

It may be easy to build, but it’s still full-featured and high-performance. If you compare it to typical Arduino-compatible kits you’ll see that it doesn’t scrimp on anything: in fact our design has more smoothing capacitors alone than the entire parts count of most other kits! It even includes a 3.3V regulator to allow it to use shields that require 3.3V, which is not something you see in typical kits.

The KitTen has the following features:

Prototyping area
For those projects where you don’t need the extra size or expense of a shield, the KitTen has its own standard prototyping area taking up a quarter of the board. Great for quick sensor and IC projects. There’s extra power pads underneath for neat connections.

LEDs visible on the edge
Wondered what your Arduino was doing? We’ve placed a blue Power LED and red D13 LED on the right edge of the board so you can see what’s going on even with a shield fitted on top.

Connector for FTDI USB cable
Use a commonly-available FTDI USB cable (not included) to upload sketches to your KitTen directly from the Arduino IDE.

Overlay guide where you need it
When you’re soldering your project, it’s good to know what you’re connecting to! All of our boards and shields have a thorough pinout and guide printed on the bottom as well as the top, so when you’re soldering underneath there’s no need to flip the board over constantly.

Top spec MCU
Every KitTen includes the higher specification ATmega328P Microcontroller, and we’ve pre-loaded it with the Arduino bootloader. Just plug it in, launch the Arduino IDE, and you’ll be running your own programs in no time.

D13 pin works for everything
The digital I/O pin 13 functionality has been fixed: the D13 indicator LED is isolated from the D13 pin using a MOSFET so that it no longer loads up this pin when you use it as an input.

Mounting holes and power pads
We’ve included a fourth mounting hole in the bottom left in the same location as the fourth hole on the Arduino Uno so there are no more wobbly board troubles if you’re fitting it to a case. Helpful markings for the power jack size, polarity and voltage are right there on the board when you need them.

5V and 3.3V voltage regulators
Many Arduino-compatible kits don’t provide both 5V and 3.3V voltage regulators, preventing you from using shields that require a 3.3V supply. We’ve included both 5V and 3.3V regulators to ensure the KitTen is compatible with all Arduino shields.

It’s all in the same place
The power jack, headers and ICSP are all in exactly the same location as Arduino standard boards. The KitTen is perfectly compatible with all Arduino Duemilanove shields, projects and sketches.

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What’s in the box?

• Gold-plated Freetronics KitTen PCB with overlay on both top and bottom.
• A top-spec ATmega328P MCU pre-loaded with the Arduino bootloader.
• All the required supporting parts.
• The fully illustrated KitTen Assembly Guide.
• Our Getting Started guide.

You will also need a 5V FTDI USB-to-Serial cable to upload sketches to your KitTen once it has been assembled. You only need one FTDI cable no matter how many KitTens you build.

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So as you can see there is the opportunity to win some great prizes. As with any other competition, there needs to be some rules:

• Prizes will be sent via regular Australia Post air mail;
• Winners outside of Australia will be responsible for any taxes, fees or levies imposed by your local Governments (such as import levies, excise, VAT, etc.)
• If you have won a previous competition you cannot enter;
• If you know me in real life you cannot enter.
• The Judge’s decision is final with regards to any dispute.
• Entries will be accepted until 2359h GMT on 28th February

So have fun and keep checking into tronixstuff.com. Why not follow things on twitter, 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.

Once again, thank you to our generous competition sponsor Freetronics!

Otherwise, have fun, stay safe, be good to each other – and make something!

Project – Simple RFID access system

In this tutorial you can make an RFID access system. It’s very simple and can be used with a wide variety of end-uses.

Updated 18/03/2013

The purpose of this project is to prototype a basic RFID access system. Although it is not that complicated, this article is my response to a kit reviewed in the Australian “Silicon Chip” (November 2010) electronics magazine. Their article describes the kit in detail – operation, schematic, use and installation. However the code for the microcontroller (PIC16F628A)  is not published due to the kit manufacturer holding copyright over the design. This is a shame, as many organisations have been quite successful selling open-source kits. So instead of moaning about it, I have created my own design that matches the operation of the original, instead using the ATmega328 MCU with Arduino bootloader. Consider this a basic framework that you can modify for your own access system, or the start of something more involved.

original article

There are pros and cons with the original vs. my version. The biggest pro is that you can buy the whole kit for around Au$40 including a nice PCB, solder it together, and it works. However if you want to do it yourself, you can modify it to no end, and have some fun learning and experimenting along the way. So let’s go!

The feature requirements are few. The system must be able to learn and remember up to eight RFID access tags/cards, etc – which must be able to be altered by a non-technical user. Upon reading a card, the system will activate a relay for a period of time (say 1 second) to allow operation of a door strike or electric lock. Finally, the RFID tag serial numbers are to be stored in an EEPROM in case of a power outage. When a tag is read, a matching LED (1~8) will show which tag was read. There are also two LEDs, called “Go” and “Stop” which show the activation status. The original kit has some more LEDs, which I have made superfluous by blinking existing LEDs.

This is a simple thing to make, and the transition from a solderless breadboard to strip board will be easy for those who decide to make a permanent example. But for now, you can follow with the prototype. First is the parts list:

• Atmel ATmega328 with Arduino bootloader;
• 16 MHz resonator (X1 in schematic);
• ten LEDs of your choice;
• two normally-open push buttons;
• two 560 ohm resistors (all resistors 1/4 watt);
• one 1k ohm resistor;
• three 10k ohm resistors;
• one BC548 transistor;
• three 0.01 uF monolithic capacitors;
• one 100 uF electrolytic capacitor;
• one 1N4004 diode;
• Microchip 24LC256 EEPROM;
• 125 kHZ RFID module;
• 125 kHz RFID tags/cards;
• connecting wire;
• large solderless breadboard;
• LM7805 power regulator;
• relay of your choice with 5V coil (example).

When selecting a relay, make sure it can handle the required load current and voltage – and that the coil current is less than 100mA.

If attempting to switch mains voltage/current – contact a licensed electrician. Your life is worth more than the money saved by not consulting an expert.

And here is the schematic:

Here is the prototype on the solderless breadboard. For demonstration purposes an LED has been substituted for the transistor/relay section of the circuit, the power regulator circuitry has not been shown, and there are superfluous 4.7k resistors on the I2C bus. To program the software (Arduino sketch) the easiest way is by inserting the target IC into an Arduino-compatible board, or via a 5V FTDI cable and a basic circuit as described here.

The Arduino sketch is also quite simple. The main loop calls the procedure readTags() to process any RFID tag read attempts, and then monitors button A – if pressed, the function learnTags() is called to allow memorisation of new RFID tags. Each tag serial number consists of 14 decimal numbers, and these are stored in the EEPROM sequentially. That is, the first tag’s serial number occupies memory positions 0~13, the second tag’s serial number occupies memory position 14~28, and so on. Two functions are used to read and write tag serial numbers to the EEPROM – readEEPROMtag() and writeEEPROMtag(). The EEPROM is controlled via the I2C bus. For a tutorial about Arduino, I2C bus and the EEPROM please read this article. For a tutorial about Arduino and RFID, please read this article. The rest of the sketch is pretty self-explanatory. Just follow it along and you can see how it works. You can download the sketch from here.

 
And finally, a quick video demonstration:

So there you have it. I hope you enjoyed reading about this small project and perhaps gained some use for it of your own or sparked some other ideas in your imagination that you can turn into reality.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, 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.