Controlling a Relay
In this project, you'll learn how to connect and control a relay. A relay is simply a switch that is capable of turning on high-power devices such as 120V AC.
A relay is a switch that is controlled by an electromagnet. When the electromagnet is energized the switch is turned on, otherwise the switch is turned off. So controlling a relay is similar to controlling an electromagnet. The switch portion of the relay consists of three connections: normally open (NO), normally close (NC), and common.
Parts needed:
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1 | The symbol for the relay is shown on the right. Notice that the left half of the symbol is the same as that for an electromagnet with the two connections for it.
If you have not already done so, you may want to first read about the electromagnet before you continue. The switch portion of the relay has three connection terminals: NC for normally closed, common, and NO for normally open. When the relay is not energized (i.e. the electromagnet is turned off) the common terminal is connected to NC, and when the relay is energized (i.e. the electromagnet is turned on) the common terminal is connected to NO. | |
2 | Making the connections for the relay electromagnet
Follow the schematic diagram shown next to connect up the relay electromagnet.
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3 | Code.
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4 | Making the connections for the relay switch
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