ABK1132
I need help, please -- I have a time delay-off relay to control the water pump cool-down cycle.
The issue is that the trigger contact requires a 1-second pulse to activate its 20-minute cooling cycle. But if power stays on, the cycle will not activate. I need a circuit or device that will act as a momentary contact switch and then reset itself when the power to its trigger goes off. The original system had a momentary contact switch, which is being replaced with a timer. Unfortunately, the timer supplies a constant current.

 

The control circuit is 110V AC

 

ABK1132
I need help, please -- I have a time delay-off relay to control the water pump cool-down cycle.
The issue is that the trigger contact requires a 1-second pulse to activate its 20-minute cooling cycle. But if power stays on, the cycle will not activate. I need a circuit or device that will act as a momentary contact switch and then reset itself when the power to its trigger goes off. The original system had a momentary contact switch, which is being replaced with a timer. Unfortunately, the timer supplies a constant current.

That seems like the solution is a different control circuit. Probably a scheme sensing the temperature to be cooled, that switches off the cooling pump power when he temperature is adequately reduced would be a better choice.

 

Unfortunately, the timer supplies a constant current.

Is the output from the Timer a dry relay contact or 110 vac?

 

Using the N.O. contact of a DC relay with a capacitor in series with the coil will provide a short pulse. The length of the pulse depends on the capacitance, so some experimenting may be required .

 

also need a bleeder resistor so that capacitor is discharged reasonably fast.