imer for switching off the motor pump

[pgr2002]

Timer for switching off motot pump

I need a circuit to switch off the motor pump after say 10 minutes. The circuit should use DC power from button cells of 3v or 6v or even 9v.

 

[d123]

Re: timer for switching off motot pump

Hi,

What's the motor voltage, is that also 3/6/9VDC? I imagine not.

If the precise time or liquid level isn't critical, use a low voltage timer IC like the LMC555 in monostable mode and a relay to disconnect the pump, or the CD4060 instead of the 555 if you have 6VDC.

 

[thannara123]

Re: timer for switching off motot pump

Look here https://www.electronicshub.org/adjustable-timer/

 

[BradtheRad]

Re: timer for switching off motot pump

I wanted to make a timer that turned off a car's dome light after a few minutes. I used a 555. I managed to get 2 minutes delay with an RC combination of 100uF & 1M ohm.

You state you want 10 minute delay from an RC, and 3V from button cells...
Then you'll need to experiment with values that apply sufficient current to the capacitor. In case you try an old large electrolytic capacitor, beware that it may have developed internal leakage, which alters its charge/discharge characteristics.

 

[pgr2002]

Re: timer for switching off motot pump

The motor voltage is 240v AC. The circuit should run on minimum between 3v to 9v to keep it precise.

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Look here https://www.electronicshub.org/adjustable-timer/

Thanks, but the circuit runs on 12v and not as required by me from 3v to 9v

 

[d123]

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.