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2-Wire Control

Two wire control is usually used for a simple ON/OFF device such as a toggle switch, float switch, thermostat, or other device that would switch off of a high/low limit.  See image below for an example of 2 wire control being used to pull in a contactor to start a 3 phase motor.  When the 24VDC relay energizes, it pulls in the R1 contactor that feeds three phase power to the motor.


Trainer Exercise:

  1. Wire your trainer so that pressing Push Button 1 energizes the contactor.  Then wire one of the contacts in on the contactor to turn on Light 1 whenever the contactor energizes.  Use the above diagram to help you figure out how to wire it.