cicuit help

[SCHEMATICS LTD.]

I am trying to mak a 12v/dc cordless drill motor have an on/ off cycle.
i would like to have a circuit like in a windshield wiper delay. I need adjustable on/off intervals.
any ideas?

[H500]

A 555 timer driving a mosfet.

[TinkerDJ]

If your handy try a pic or avr with an on off output to run a fet. But the 555 is likely easier. If you look at the schematics avaliable on the internet and search on 555 you should come up with a circuit that has an adjustable output. The one i have is for a morse code key practice tone generator. I don't know if you could combine that with a fet. I think it runs to fast but it could be slowed down.

Here's a couple of sites might help with the idea.
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
http://home.cogeco.ca/~rpaisley4/LM555.html

Here i found one that has exactly what your looking for.
http://www3.telus.net/chemelec/Projects/PWM/PWM.htm