Electronics 2000

I would be grateful for a little advice, please.

I am rigging up a rainwater catchment system to supply a washing machine. I need (due to lack of pressure) to pump water to the washing machine (using a 12v submersible pump). So that the pump is only activated, when needed (to supply the washing machine), I have an idea. Through the normal operation of the machine a solenoid is activated to open the water supply valve and another 'signal' closes the valve once the water level is reached. I want to use these electronic signals (to the washing machine water inlet valve) to switch the pump on and off. How would I do this, what components would you suggest ? The pump will be supplied by a lead/acid battery with its own charging circuit (which will be eventually be connected to a solar cell arrangement.)

All suggestions, ideas etc would be very much appreciated.

Thank you
David

With regards the water inlet valves , the 'default' would be closed, when energised open. So there is no signal to the valve solenoid to switch on or off.....my mistake. Literally there is current or no current to the solenoid (Washing Machine) ....it is this that I need to switch the pump on and off. Basically I need the power 240V (that is used to actuate the washing machine water valve) to 'switch on the 12v low wattage water pump. Once the valve is switched off (via the washing machine's water level sensor) power will no longer flow to the valve and want this to switch off the pump (default for the pump would be 'off')
During a washing 'cycle' the pump would be activated 4-5 times for approx. 3 minutes each time. Would a step down transformer wired to the water valve work ? a relay fitted into the circuit ?

Thank you
David

Hi,

Yes, you could power the pump via a transformer from the machine, the only risk being that the pump will probably draw more power than the solenoid value, so you could overload the switching capacity of the washing machine's controller output. You need to check the current consumption of the pump at 12V and from this calculate the tranformer's primary current at 240V. Clearly you wouldn't then need the battery or charger.

Alternatively a relay with a 240V coil (or a lower voltage fed from a transformer) could switch the pump powered from the battery. Be certain to provide adequate isolation between the mains and battery circuits if you do this. The relay would need to be enclosed, and all wiring inside the enclosure should be insulated to mains voltages.