Take a look at Beau Schwabe's web site at
http://www.ionet.net/~bschwabe/BasicStampII/UV-timer.gif , he has just
posted a schematic to do just what you are looking for, but I think he
used a PBasic compiler to do the code.  But it will give you an idea.
later..

Robert Powell wrote:
>
> Speaking of eprom erasers... I just bought a Datarase 2 without the
> timer and thought a first PIC project could be to add a PIC controlled
> timer to the thing. (I know, I know... the timer was an extra 10
> bucks, and my time is supposedly worth more than that... but I wanted
> something fun to do! :-) I don't want to mess with LCD panels or
> keyboards yet. I want to keep this project simple. I thought a push
> button to select duration, a go/no-go push button, and some LEDs to
> show time selected/time remaining on the erase cycle. So here are a
> few questions:
>
> If I use the internal RC osc. will I get semi-stable timings? (If I
> dial in 7 minutes I'd like to get within 20% of that 7 minutes)
>
> Any shortcomings on using the Datarase's power supply to power the
> PIC? (I forgot to look to see what it puts out; any ideas how much of
> it is used by the eraser?)
>
> Any suggestions on which PIC to use? (I thought a 16F84 would be nice
> piece of overkill; how 'bout a 12C50x?)
>
> Thanks for your time.
>
> Robert Powell
> Programmer Analyst
> Hollywood Entertainment
> 25600 SW Parkway Center Dr.
> Wilsonville, OR 97062
> (503)570-5307


Alvin Tan

mailto:Alvin_Tan@bc.sympatico.ca