Toggle Switches

Toggle switches are available in various contact configurations. Each switch consists of one or more poles, where each pole is actually a separate switch.

The switch contact configurations include:

Single-pole/single-throw switch (SPST)

This is the simplest switch. It has a single set of contacts that can either open or close. Its contact configuration is illustrated below:

Single-pole/double-throw switch (SPDT)

The contact configuration of this switch is illustrated below:

The switch has a movable arm called common (c) that can connect with either contact A or B.

You can also read: Solid-state Relays (SSR) Features and Operation

Double-pole/double-throw switch (DPDT)

It consists of two electrically separate SPDT switches in one housing that operate together.

Toggle switch contacts have a maximum voltage and current ratings for AC and DC operation. A toggle switch can handle less DC voltage than AC voltage at rated current, for instance, a switch might be rated at 5A for 125 Vac or 5A for 28 Vdc. The reason for the difference is that when the contacts are just opening, the current will continue (for a short time) to arc across, which tends to burn and pit the contact surface. AC will arc less than DC for the same voltage because AC voltage is going 0 V twice each cycle. Additionally, most toggle switches have a ‘snap’ action which pulls the contacts apart rapidly to minimize arcing.

You can also read: Electromechanical Relays (EMR)