I have an on demand water pump that is controlled via a simple push button switch which momentarily shorts a 12V circuit to activate the pump for a set period of time. I want to replace this switch with something to do the same job, via an RF remote. I have looked at the various relays online. e.g. this one,

https://www.amazon.com/Switch-Wirel...ansmitters/dp/B071WM1YGS?ref_=ast_sto_dp&th=1

but I can't figure out how to wire it for this situation, or even if it could work at all. The 12V supply that the relay requires would be supplied by the two wires from the pump controller that require to be shorted. Normally you would also then connect further wires to the relay from the device that you want to be controlled. But there are no such wires in this case. Presumably also, shorting the wires that are providing power to the relay would be rather like sawing off the branch you're sitting on, inasmuch as that would also cut the power to to the relay, presumably.

So I guess I'm concluding this device can't work, and I need something else. Am I wrong; is there some other solution?

Thanks in advance and please go gently, I know nothing!

 

You need to permanently apply 12 VDC power to the receiver at the IN+ and IN- terminals.
Your connections to the pump go to COM and NO.
The receiver needs to be programmed in order to select the function, momentary, latched, or toggle.
To be honest, I don't know what is the difference between latched and toggle.

 

OK, yes, I figured I probably had to supply the 12V separately.

Many thanks!

 

The relay doesn't need to be 12 volts. It can be any voltage you have available. If you have 24VAC then you select a relay rated for 24VAC continuous duty. If you have 5 volts DC available then you select the relay rated for 5VDC continuous duty. I say continuous duty because its designed to handle continuous duty even though you may only momentarily use it. Things like horn relays in cars are not rated for continuous duty whereas the relay that powers the fuel pump has to run as long as the car is being driven.

As for the question "will this work?" it should. The switch is just two contacts that are closed when you flip the switch or push the button of a momentary PB switch. The relay just replaces your finger. It's electrically controlled. @MrChips said it short and sweet. Where you close the switch to start the pump - the relay will do the same job. Only it's controlled by a control voltage. Could be a battery powered circuit or a continuous powered circuit.

 

There's a separate 12V supply off the pump controller that I can use. Just means running more wire as I don't have an outlet where the relay will be situated. I have to run the wire for the switched circuit anyway, so no big deal.

Thanks again.

 

If you are using a common remotely controlled wireless switch for this sort of application, YOU NEED TO VERIFY that the control terminals are actually isolated from the receiver power connection. THAT DETAIL is seldom mentioned in the amazon product listings, and if the two connections are not isolated there may be problems.