Do a web search for NE555. Google just gave me 332,000 hits on it.
This is a little 8 pin integrated circuit that can be wired to do various timer functions. It should work for you. That is, if I understand what it is you are trying to do.
If you have even basic knowledge of how to wire a circuit you should be able to make use of this. The timing is controlled by a capacitor and one or two resistors. The resistors could be made variable or switchable for adjustment purposes. If you need to control a valve or pump you will probably also need a transistor. This device works on DC so you will also need a power supply. A wall wart would do.
There is also a dual version in a 14 pin (or is it 16?) package, but I do not recall the number---its been a LONG time since I did any work like this.
Jim
|