IR reflective tachometer

I had an urgent need to build a simple tachometer. I decided to build one I have already made (although it's avr based) and share the result with you. The project is based on the one that could be found here: http://www.forbot.pl/...24.htm This link contains schematic and both source code and compiled binary file. I just added a 7660s negative voltage converter for LCD polarization.

The IR diode flashes to the rotating element. Once the passing field is black, the IR beam is not being reflected. When it's white, IR reflects, goes back to the phototransistor and activates its current flow. The processor detects the event of white field passing and counts the events, divides by time and displays the result in revolutions per minute.

Phototransistor and an IR diode in one housing. Heat-shrink minimizes IR beam leaks:

IR can't be seen normally, but it's cool how the camera-eye allows us to watch it. Check out your remote controller.

How it works:

If you would like to build one, be aware that you should pull-up reset pin to VCC. Otherwise uC could be unstable.