Hello All
I have fabricated a home built fuel polishing system for my offshore sailing yacht. In heavy seas, sediment cant be agitated within the tank causing loss of engine power at the least opportune moment. Wonder if you could assist with a circuit design for momentary push button initiating a three hour timer. This will activate a bypass fuel filtration circuit to hopefully catch any particulates before they kill engine power.
Criteria are:
low parts count
Zero standby draw
everything suitable for potting

Three hours as this should be enough to pass entire 200liter fuel volume through filter at least once.
Thanks for any and all assistance!

 

A timer like this should do what you want.
To initiate the timer with a push button, use Schematic Diagram 2, which turns the relay on when started and off at the end.

Use a DPST or DPDT relay and connect one set of the NO contacts in series with the power to the circuit.
Connect the start push button across the contacts.
Then when the button is pressed, power is applied to the circuit and the relay closes, providing parallel power to the circuit until the circuit times out and the relay opens.
The reset PB shown is not needed.

There are also timer modules that could likely be used, such as this or this.

 

A timer like this should do what you want.
To initiate the timer with a push button, use Schematic Diagram 2, which turns the relay on when started and off at the end.

Use a DPST or DPDT relay and connect one set of the NO contacts in series with the power to the circuit.
Connect the start push button across the contacts.
Then when the button is pressed, power is applied to the circuit and the relay closes, providing parallel power to the circuit until the circuit times out and the relay opens.
The reset PB shown is not needed.

There are also timer modules that could likely be used, such as this or this.

Thanks indeed for the response although seems to be a dead link?

 

seems to be a dead link?

Works for me.

 

Doesn't work for me either.

 

Doesn't work for me either.

Which links?

 

Your first link.

 

How about this?

 

That works.