If you are new to microcontrollers then this project may be a good start. It includes 6 seven segment LED displays and four LEDs for colons. It uses couple buttons to set up time.

Project doesn’t use separate RTC chip. So time is generated inside AVR what leads to some error (1 second a day isn’t bad at all).

Having cats and dogs under one roof may be a problem some times, because they like to sneak around and share each other’s food. So the only solution is to make some kind of a barrier so dog would be kept away from cat’s food.

Setup I based on AVR microcontroller and it uses an infrared trip-wire system that distinguishes dogs from cats. In this case dog is bigger than cats, so it is pretty easier to recognize when dog passes. System reject short interrupts of beam as it supposes to be cat’s tail. Anyway what’s left is to find an annoying sound to play during alarm so dog would hate it and run away. Simple, cheap and effective!

Doing some robotics experiments or other automation tasks may require a good interface to computer. Why buy one if it can be built pretty easily. So here it is – an eight channel servo controller board with USB interface. This means that you can develop pretty complex mechanism with servos and run them via PC. It is based on ATmega168 microcontroller and FT232RL chip.

The project is homemade PCB with hand soldered SMD components. AVR microcontroller is programmed by using AVR-GCC compiler which is free and open source tool. Should be no problem to replicate the project and do some great stuff with servos.

Tachometers are devices that are used to measure spinning speed that is expressed as RPM (revolutions per minute). You can find tachometers almost in all cars. But sometimes there is a need to find out RPM for different objects like in modeling, robotics, bicycles etc. It is better to use a contactless tachometer because there isn’t always an option to measure spinning speed directly. So here it is – a simple contactless tachometer project where RPM of rotating shaft is measured with IR sensor.

Simply you need to stick a reflective sticker on a rotating part and then place an IR opto-couple which sends IR beam and then detects reflective changes. The rest part is left for AVR ATmega microcontroller which actually rejects noise from signal and then calculates RPM value which then is displayed on LCD display. You can download all project files ready to build your own, or buy a ready preprogrammed kit to go along with less effort.

Nokia 3310 LCD are still popular as they are simple to interface and you can find tons of software examples for various microcontrollers. But to push things further there is a nice instructable submitted by wkter. This time display is connected to AVR ATmega8 microcontroller that has software based USB (AVR-USB) that talks to PC.

This way you can easily send various messages or even graphics from any PC with libusb drivers installed. Anyway don’t expect much as USB is pretty slow, but ideal for displaying some information like feeds, tweets or other computer related information. Instructable is greatly explained and has all references needed to push forward.