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Turn LED off when switch closes

ThomsCircuit

Well-Known Member
The group here helped me design this circuit last year. It works great. The valve remains closed until both S1 & S2 close then, once the valve opens, it remains open until both switches open again. I understand that by design the MIN FILL switches (S2) LED (LED3) will not turn off until both switches open again but id like to alter the circuit so LED3 turns off/on as S2 opens and closes. I believe a transistor can help here but I'm not sure how to connect it. Can you guys offer some guidance?

Thank you.
T.B.
WaterSensor2 - Project-1.png
 
Last edited:
WaterSensor2 - Project-1-diode.png

You can add a diode like that. LED 3 will turn on and off with S2, as long as S1 is closed, which I think it usually is.

Most of the time, S1 will be closed and S2 will be open, so LED4 will be on most of the time and LED3 will be off most of the time.

Each time S2 closes and the valve opens, LED3 will only be on for the time it takes for the water level to increase enough for S2 to turn off, which may be a very short time. If the water is being disturbed by the ducks (https://www.electro-tech-online.com...ler-for-dr-fluffy-bottoms-quack-house.164184/ in case anyone hasn't seen the previous thread), then S2 could turn on for a very short time, and the valve would open. It would only take a few ms for the relay to operate and it would be quite difficult to notice that LED3 had turned on at all. Of course, LED5 would be turned on for however long it takes to fill the tank.
 

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