MPN

Switches

Switches are commonly used in electronic circuits. They enable control of the circuit by switching it on/off or controlling a range of other features.

How do they work?

Electronic switches are binary devices which sit within a circuit to control the flow of electricity. They work by interrupting the flow of electrons and switching the circuit on or off.

Switches contain terminals which connect to metal contacts. When the terminal and contact are touching, the switch is closed and the current can pass through. When the terminal and contact are not touching, the switch is open and the current cannot pass through the circuit.

What are Poles and Throws?

The number of circuits controlled by a switch is referred to as "poles". The number of positions that the switch can adopt is called "throws". The combinations of these are:

SPST (Single Pole Single Throw)
SPDT (Single Pole Double Throw)
DPST (Double Pole Single Throw)
DPDT (Double Pole Double Throw)

What types of switches are there?

The type of switch you require depends on the connections you wish to make within your circuit. Switches are often grouped by the way they are operated, for example, rocker switches that rock side to side. Alternatively, they are classified by their application, for example, keypad switches are used with keypads. Here are some examples of switch types: