Table of Contents
Relays are mechanical switches that are controlled electrically.
- A double pole switch has 2 independent switches in it.
- Double throw switches have 2 terminals that the switch(es) alternate being switched to. Usually one is normally closed (on) while the other is normally open (off). Other switches stay in the position they were last set to.
- Applying the rated voltage to the relay coil energizes it. At that time, the common (com) terminal pole switches from the normally closed position to the normally open position. While the coil is energized, the normally open terminal is closed.
- Cutting power to the relay coil returns the com terminal pole to connected to the normally closed position from the normally open position. The coil is an inductor, which means that it won’t stop conducting current instantly. Therefore it should have diode that is parallel to it. The diode needs to be reversed biased when supply voltage/current is applied. While energized, the coil will feed current back to itself through the diode, right after power to it has just been cut off.
Relay Modules:
You don’t have to wire up a relay yourself. Prebuilt modules are easy to get and affordable. You simply screw down wires from other circuitry to them.
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