If you really want to build a timer from scratch, this foum is the perfect place for advice.

But if you just want to get on with it, then I agree with Blocco - there are hundreds of repeating timer and cycle timer modules on ebay, some with analog adjustments, some with digital displays. Many can run directly off of vehicle power and have a relay output. That is a lot of functionality for very little effort.

ak

 

Something like this.

http://m.ebay.co.uk/itm/271250966413?_mwBanner=1

Change the preset to give you a longer time delay.

 

You can buy this timer on eBay for $5.00 post free.
http://www.ebay.com/itm/5V-12V-DC-M...911625?hash=item3f529c4109:g:jPwAAOSwu1VW6Alv