Countdown timer
Okay, this is neither really advanced nor interesting, but I promised to publish every single project I make. ;-)
What could it be useful for?
- Paintball or LARP scenarios
- Egg timer
- A bomb?
Hardware
The original device was built without any documentation. This is the best I could recover from looking at the PCB and from some old sketches I found.
Download it in the Eagle format if you like. The exact component values/models are not critical, just grab some PNP transistors, 2K resistors and four common-anode LED displays. The XTAL I used was 11.0592MHz, if you change it to a different value you will need to alter the delays accordingly.
Firmware
Note: the timer isn't totally accurate, I just threw some code together that appears to work. It may lose a second or two every minute. Think about this as some kind of "Microsoft Minutes", if you've ever installed Windows you'll know how inaccurate they can get sometimes. I haven't really dug into this issue, as such accuracy was sufficient for my uses.
Known issues
- innacurate (too lazy to fix)
- doesn't reset itself at start (too lazy to solder a 1uF capacitor)
- some additional features would be nice, eg. a RTC
Downloads
- firmware sources [tgz, 2KB]
- a short video [avi h264, 7MB]
Sample use
