How to Wire a DPDT Switch

This is a DPDT switch. There are two movable contacts, and each contact has two possible positions.

Electrical switches come in a wide variety of configurations. The abbreviations used to describe these configurations are somewhat cryptic, and the packaging or instruction sheet that accompanies the switch is often of little help. Switches are identified by a P, or pole, number and a T, or throw, number. The pole number indicates the number of movable contacts on the switch, and the throw number indicates the number of closed positions for each switch circuit. So, a DPDT switch has two poles and two throws (D stands for double).

Instructions

1. Visualize your switch as two separate switch circuits that are controlled by the same knob. Each circuit of a DPDT switch allows you to select which of two inputs will be connected to the output.

2. Label the terminals of your switch. You can put labels directly on the switch or make a labeled drawing. The labels should be something like this: Circuit 1, Input 1; Circuit 1, Input 2; Circuit 1, Output; Circuit 2, Input 1; Circuit 2, Input 2; Circuit 2, Output. The output terminal is attached to the movable contact of the switch, and the two inputs are the terminals that the movable contact can be connected to.

3. Connect the signals you want to choose between to the two input terminals of Circuit 1, and connect the output terminal to whatever you want to control. Do the same for Circuit 2. For example, one input is connected to a 6 Volt battery and one is connected to a 12 Volt battery. The output is connected to a small light bulb. By moving the switch, you could change the brightness of the bulb, because a higher voltage will drive more current through the bulb, producing more light.

References

• University of Alabama: Mechanical Engineering: Proximity Switches
• University of Washington: Digital Input

Resources

• 1728 Software Systems: Basic Electricity Tutorial