Accelerometers are found in many devices even smart phones. They are cheap but plays significant role where motion, acceleration or inertial position detection is involved. You can get XYZ accelerometer module for like $3 from eBay. Alex made a post about his experimets with MMA7361 accelerometer model. Luckily there is an Arduino library that makes programming even easier. Practically there isn’t much about reading values – simple analog read does the business.

After small experiments Alex built acceleration activated LED blinking box. He even managed to place the circuit inside dental floss container. Instead of trying to squeeze Arduino in it, he’s chosen smaller micro – Attiny45 which fits nicely. It is powered from 3V coin cell battery. Just a nice quick project for an evening.

Today modern cars are equipped with outside and inside thermometers. But some older ones are missing this feature. Sometimes it is good to know what temperature is outside while driving. You can stick one of those gadgets on your windshield. But why buy, if you are capable of building a decent thermometer using small micro. Check out this thermometer based on DS18S20. Attiny2313 microcontroller does the reading of temperature value and displays it on LCD.

Since thermometer is gonna be used in the car. Special care is taken when designing power supply part. It’s a noisy environment where voltages can spike up to 40V. An LM2574 regulator is used with inductive and cap filtering to get stable 5V supply. Original design was intended to be used in Dacia Duster. Bright LCD nicely fits in free space on panel.

I don’t know if very tiny tools like programmer adapters are very handy to use, but it is always fun to watch how tiny they can get. Philip took a vusbtiny programmer and squeeze it in to smallest PCB he could make.

So, he made USB connector directly on PCB by tracing pads on it. But to be sure, on other side he made footprint for Mini USB socket. If one fails there is a way out. Of course all parts are SMD except the 6-pin ISP connector. The board size come to be 12mm x 28mm and I think, there still is a space to squeeze a bit by making ISP header smaller (use 1mm instead of 2.54mm) or choosing smaller passives instead of 0805. But would such tool be normally useable?

RFID readers aren’t very expensive to buy. But if you are real hobbyist and like building instead of purchasing stuff, then Attiny13 based RFID reader might be interesting to experiment with. It was build by Vassilis Serasidis – author of many great projects. As always he tries to keep things simple, cheap and easy to follow. The RFID reader he builds works with standard 125kHz tags that uses EM4100 protocol.

There is a good explanation on how the circuit works in physical level. It includes how reader transmits data and receives from passive tag. Reader is assembled on prototyping board using through hole components and hand made coil on the back. You will also get some understanding how to calibrate coil to have great range and reliability. Currently reader outputs the 10-digit Tag serial number via Serial interface 2400 bps 8N1.