![]() ![]() The schematic below should let you visualize this pretty well: A Normally Closed relay opens when the electromagnet is activated, and vice versa for Normally Open relays. Relays can be designed as either Normally Closed or Normally Open. When the control board applies a low DC voltage (often 12 VDC) to the coil, it creates a magnetic field which pulls on a metal arm, actuating the switch. They use the property of electromagnetism to allow a low DC voltage to physically change the position of a switch, thereby either opening or closing a high-voltage AC circuit.ĭid you ever make an electromagnet in school by wrapping a wire around a piece of metal and connecting the wire to a battery? Well that kind of electromagnet is almost exactly the same kind used in relays. Relays: The older and simpler of these two devices, relays - more precisely called "electromechanical relays" - are very simple devices. ![]() ![]() They pull this off by using relays or triacs, devices that all of us are at least passingly familiar with.īut how do these very common control components work, exactly? And how is troubleshooting a relay different from troubleshooting a triac? That's what we'll look at today. Whether a control board in an appliance is simple or sophisticated, there's one trick it has to pull off: switching high AC voltage using low control voltage. ![]()
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