Selector switches are electrical devices with operators that are manually turned to activate electrical contacts. These types of switches are usually found in front of control panels in various domestic applications.
They are the knob on your audio devices that you turn to set the audio source to radio, Bluetooth or aux and on your blender to change the speed setting. They are also found in industrial machineries allowing users to switch between manual and automatic operation, temperature settings, primary and backup power, etc. You’ll also see them on washing machines, ovens, guitars, HVAC systems, security systems and even toys.
They can be used to set different modes, choose between different channels, select between different power sources, switch between different light settings, change speed settings, etc. It all depends on the application.
What are the components of a selector switch?
Selector switches fundamentally comprise a spindle or rotor featuring a protruding Spock. Typically, there’s a rotary knob attached to the rotor or spindle, and then a contact block holds everything together. On the inside of the contact block there are many terminals.
How a selector switch operates?
As mentioned, selector switches are typically found on control panels. They have many different potential contact combinations.
For example, a selector switch can be a basic two position switch used to turn a machine on and off or select between manual and automatic operation. In such a setup, the operator simply needs to twist the rotary knob to place the switch in the desired position. Twisting the rotary knob rotates the spindle, too, such that its protruding Spock claps onto the desired terminal changing the machine’s electrical state to on or off.
Alternatively, the switch can be three-position allowing the user to switch from an off position to a manual or automatic position. These types of switches have two contact positions, too, for manual and automatic settings. The rotary knob can be rotated such that both contacts are open (device is off), the manual contact is closed or the contact for automatic is closed.
Using truth tables to illustrate selector switch positions
One can use truth tables to illustrate contact position on selector switches. For example, there are only two contacts in a basic ON/OFF switch. The first contact can be the ON terminal, while the second contact serves as the OFF terminal.
Consequently, if the switch is set to ON the first contact is closed (X) while the second contact remains open (zero). when the knob is turned the other way the second contact is closed (X) and the first remains open (zero).
But in a three-position switch there are two contacts but three ways to set the Spock. The first contact can be the manual terminal while the second contact serves as the auto terminal. With the switch set to OFF, the Spock does not clasp any of the contacts, meaning both contacts are zero.
When the switch is set to manual, the Spock clasps onto the first contact and it remains closed (X) while the second contact remains open (zero). With the knob set to auto the first contact is open (zero) while the second contact is closed (X).
Momentary vs. maintained selector switches
Some selector switches are maintained switches such that the knob stays where you leave it and only returns by a counter-twisting motion. On the other hand, some selector switches feature spring return mechanisms for momentary operations. Momentary selector switches automatically return when let go.
You can also pick between short handle selector switches and the long handle kind. Short handle selector switches are less conspicuous while long handle selector switches are easy to handle.
Selector switches can also be illuminated or non-illuminated, with the former featuring LED indicators for the on and off position.
Selector switches are simple yet useful in setups where one needs to switch between different power sources, speed settings, temperature calibrations, audio sources, sound effects or just manual and auto operation.
If you are looking for selector switches for your electrical and electronic application, we will be happy to talk to you about our product varieties. We specialize in various switch designs for clients with unique project requirements. Let us know what you are looking for, and we’ll be happy to get it for you.