Timer 001
Dim writes –

This Timer was originally build for my PCB exposure box but it can be used for other purposes. You can set the time between 1 and 90 minutes by pressing the up or down switches. The countdown starts by pressing the on/off switch. By pressing this switch again you can interrupt the prosess at any time you want. After the time elapsed the timer gives an alarm sounding the end of the prosess and disconnects the load.

By pressing the on/off switch you reset the timer and it’s ready for another lap.The 2X16 Lcd display informs you about the remaining time during countdown and other informations about the operation of the timer. I used an AT90S2313 in my first prototype but then i change to ATTINY2313.

AVR countdown timer – [via] Link.