Hi everyone.
I have a pump controller which turns a relay on and off to drive the pump.
Attached is a circuit diagram for the part in question to the best of my examining the actual circuit.
The original relay was a 24v 1200R 40mA one.
The voltage across the relay was about 19v oddly considering there is a 24v zener there and was not *quite* firing the relay properly though obviously it must have at some point. The Zener appears fine. I think that's due to the super simple half wave rectifier.
I thought I could just use a 12v 300R 40mA relay and put a series resistor in line with the relay to make it work off the 19 available volts. However I only get about 6v across the coil at 20mA which clearly is not enough - almost exactly half of what I need!
Not enough resistance in the relay to cause enough of a voltage drop across it to fire it up now that it's only 300R I suspect.
Any ideas how I can make this work easily without reworking the entire power supply (which is also used in other parts of the circuit so I don't want to muck around with it too much in case I wreck something else in the process).
The green LED is a simple power indicator and the other one is a pump on indicator - it comes on with the relay.
Any ideas would be greatly appreciated.
Regards,
-Paul
I have a pump controller which turns a relay on and off to drive the pump.
Attached is a circuit diagram for the part in question to the best of my examining the actual circuit.
The original relay was a 24v 1200R 40mA one.
The voltage across the relay was about 19v oddly considering there is a 24v zener there and was not *quite* firing the relay properly though obviously it must have at some point. The Zener appears fine. I think that's due to the super simple half wave rectifier.
I thought I could just use a 12v 300R 40mA relay and put a series resistor in line with the relay to make it work off the 19 available volts. However I only get about 6v across the coil at 20mA which clearly is not enough - almost exactly half of what I need!
Not enough resistance in the relay to cause enough of a voltage drop across it to fire it up now that it's only 300R I suspect.
Any ideas how I can make this work easily without reworking the entire power supply (which is also used in other parts of the circuit so I don't want to muck around with it too much in case I wreck something else in the process).
The green LED is a simple power indicator and the other one is a pump on indicator - it comes on with the relay.
Any ideas would be greatly appreciated.
Regards,
-Paul
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