Common Relay Pin Configuration (Bosch-type)

Relays are widely used in electrical applications where one circuit is to be energized or turned "on" by the presence of a voltage, provided by another circuit. An example of this is when a projector turns on it has a 12V signal to let different accessories know it's on. Anywhere a switch can go in a circuit, a relay can replace it, (as long as there is a triggering voltage available to activate it).

The "switch" in a relay is more often called a solenoid or coil. A solenoid is like a piston that pushes outward when energized with electricity. This push mechanically trips the switch in the relay, completing circuit and allowing the switched voltage output.

A relay can be triggered with an electrical pulse as small as 75 milliamps. The switched output can be as high as 20 amps or more. One very useful use of a relay is to control a high current device such as a linear actuator motor with a low current signal, such as a projector or home theater controller. Another common use for relays is to separate control voltage from motor voltage. This is useful when you've got a control voltage of 12V and you want to control a linear actuator running on 36V, such as controlling the track actuators with the 4CH-RC (some wiring required)

Relay at rest

Relay energized

• 30 is the common or input voltage (or ground) to be switched.
• 87a is the normally closed connection (can be used as a switched voltage output when the relay is at rest). (This terminal offers no voltage when the relay is energized.)
• 87 is the normally open connection (switched voltage output when the relay is energized).
• 85 is connected to the ground of the triggering voltage.
• 86 is connected to the positive 12V of the triggering voltage.

Below are several common examples of how relays are commonly used:

Wiring Diagrams:

• Control an actuator with relays and a rocker switch
• Control an actuator with relays and a rocker switch and remote control