When the button is pressed the Arduino board will put pin 2 in HIGH state, meaning 5V on pin 2. This voltage is used to drive the transistor that will switch ON the relay and the load ... to introduce ...

The Barrington Model Circuit Breaker Simulator was designed to be a convenient, lightweight alternative to operating high-voltage circuit breakers while testing the operation of substation protection ...

It utilizes a current transformer, single transistor amplifier, voltage doubler detector, robust relay and capacitor limited ... some have extra space on one end for a switch, pilot light, circuit ...

Of course he could modify a refrigerator and humidifier to be controlled separately, but [Mike] decided the best course of action would be to control line voltage with an Arduino. [Mike] started ...