Make an Arduino timer

Hi, so me and my pal are setting up so we can make PCB´s. We are currently making a UV exposure box (possibly another instrucable) and for this box, we needed a timer, so this is what we have done so far, and what we are going to do.

This project is based on the ardweeny from solarbotics because its cheap (10 $) and its small (28 DIP)
it counts down from 999 to 0 (seconds)
it has a 250V 10A Relay.

here is a short video of it counting down from 30 to 0:

Step 1 Parts list

Ok so here is the parts list:

as for all items these are suggestions

*one Ardweeny (or an ATmega168/328 chip with apropriate chrystal, resistor and capacitor)
    *one USB to FTDI Adapter for programming the ardweeny (if you dont already have one)
*8 NPN transistors capable of driving 30 mA each. (We used BC547 (keep the pinout in mind!)
*3 PNP transistors capable of driving 200mA each. (We used BD136 (Odd pinout here too!!)
*3 7-Segment displays (We used KINGBRIGHT SA52-11EWA common anode)
*11 resistors for the transistor bases (i used 200 ohm resistors (!!!OBS these are not on the print, see picture in step:[comming soon])
*7 resistors for the segments (150 ohms for an output of around 20 mA)
*2 10 pin header
*2 2 pin header
*1 28 DIP socket, narrow (you could solder the chip in but i would hate to have to solder it out if something gets burned!)
*1 6V relay (if you need this to switch things on and off)
    *one protective diode (We used some 1N4007 ones we had lying around)
*1 Potentiometer (We used a 4k7 because we had one around)
*Wires... lots of wires
*soldering equipment


That should be it. on to the next step

Comments

[astroboy907]

Hey man- thanks 4 the code!! On my ible someone is asking for timer code and your code is a great start to it! What I needed was the x divides code, for the timer- thanks so much! Check my ible out, its the TimeDuino- very similar to yours, just a clock, not a timer :)

[Snuletek]

No problem, worked with it for hours till it hit me :P

sometimes less is more :D