Re: Timer for switching off motot pump
Hi,
If that means the power supply for the timer circuit can be anywhere from 3VDC to 9VDC, then you should use a buck-boost to output something like 5V, followed by an LDO. If I were you, I'd be looking for relays that comply with the coil requirements on the timer side of the circuit's and the contacts on the motor side's requirements (240VAC and 1mA or 10A?).
You could look at SSRs, but they tend to be pretty expensive compared to a relay.
Also, if you have the board space, two monostable timers in series (divide the 10 minutes into 5 minutes each) should make it more accurate, hopefully. It's better to use a lower value capacitor and a higher value resistor to keep it less "more-or-less this or that" and more "approximately 10 minutes" r.e. the constancy of the timing.
Presumably there are other solutions to this circuit that are far better.
Does your motor pump fill a tank or irrigate? I don't know what it's called, but for filling a tank there are ready-made two-wire devices that level sense, like a floating buoy or something, that are allegedly easy to fit to where the pump on/off switch is. Again, you'd have to do a bit of online research to find them.