Help with implementation of external relay with RC

Hello all!

I would first like to declare that I am not so familiar with electronics, so please bare with me.

Operation:

I have a remote controller and receiver which operates two electromotor valves. These are normally closed and when pushing a button on the controller the valves open, this part is correctly setup.

Problem:
Since the valves are normally closed, they always receive a closed signal from the receiver. The problem occurs when the valves are being opened, because the cable length is small (0.5m), the valve sends back a pulse to the receiver wich burns the circuit. This is the information I got from a service technician.

As a solution to this problem, an external relay + RC shall be implemented between the circuit and the valve to protect the circuit from the pulse.

Question:
The information regarding the external relay can be easily found online, by a quick google search. Can someone help me, with how I am suppose to connct this relay inbetween the circuit and the valves? As I have mentioned my electronic skills are poor.

This shouldnt be very difficult (from what I have been told), but I could really use some pointers. I have attached a simple diagram that show the receiver, valve and the external relay.

View attachment Circut diagram.pdf

Any help would be appreciated!:grin:

Hi

What is opening the valves a the receiver end?

I wonder if there may be back EMF from coils in the receiver?

Do you have more detail on the receiver and valve circuits?

a schematic maybe?

eT

I think eetech00 is right. The pulse sent back from the valves that "burns" the receiver is probably back emf from the inductance of the motor or solenoid or whatever it is that actually moves the valves. Here is what that means in simpler terms. When electric current is flowing through a coil (like the coil in a motor or a solenoid), that current has a sort of "inertia". It wants to keep going, and it is hard to stop it suddenly. It is like a heavy object on wheels that once you get it moving it is hard to stop. When you try to stop it, you feel great force from the thing that is moving. So with electrical current, after it gets flowing (when opening the valve), the receiver eventually has to stop the current (after the valve gets fully opened). It does that by interrupting the circuit, giving the current nowhere to go. When that happens, the inertia of that current exerts a "force" (which we call voltage) to try to keep going. This voltage appears across whatever tried to interrupt it. In this case that would be someplace inside the receiver module. We call that voltage "back emf", and it can be thousands of volts - enough to damage, or "burn", the receiver switch.

Even if you add a relay, as you are suggesting, this back emf could still be a problem. It will no longer "burn" the receiver, but it could burn out the contacts in the relay by causing a spark to jump every time the relay is opened. The solution is to use a snubber circuit, or a protection diode, depending on whether the motors are AC or DC. These protection circuits allow the current to gradually come to a stop when the motor is turned off, instead of coming to a stop all of a sudden. This prevents the spark or the high back emf, so no damage is done.

Thanks for the easy explaination

I ended up using a protection diode, as you suggested. This worked out great! Tested it around a hundred times now, by suddenly switching rotation on the valve and no problems!

My initial thought was to use the external relay as a buffer, to ensure that the pulse sent back damaged the relay and no the receiver. As I understand now this solution would not be optimal for a permanent installment.

First time using this forum, and I am very pleased with the response!