Electrical – how to make a latching circuit with ground

latchrelay

I have a pump, represented by a lamp in my schematic, i want this pump to be running once i switch the Activate switch, and when ever an alarm(i have 2 different) is triggered (Alarms are ground) the pump should stop. That is working correctly on the schematic below, there is no complication on that.

My problem is that what i am looking for is that when an alarm is fired then the pump will deactivate and won't activate again even if the alarm goes off, for it to reactivate the activate switch should go off and on again. I have been experimenting with different latching circuits but since the signals are ground i am having a difficult time achieving the result.

schematic

simulate this circuit – Schematic created using CircuitLab

Best Answer

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Tidy up of original circuit. Note how using the ground symbol removes several lines and clarifies the schematic.

schematic

simulate this circuit

Figure 2. The revised circuit.

How it works:

  • Closing the Activate switch energises the pump via RLY1's NC contact.
  • If either alarm contact closes RLY1 is energised, the pump is disconnected and the relay latches.
  • Opening the Activate switch resets the circuit.
Related Topic