Selector Switch - Basic Properties, Terminology and Theory
What is a Selector Switch?
Selector Switch works on a general principle; they contain a simple selector switch on the front of the panel, and a broad range of potential contact combinations (via the contact blocks), on the inside of the enclosure. The major difference between the selector switch and the pushbutton is that, while a pushbutton has a plate that pushes down both contact plungers at the same time, a selector switch has a rotating cam with ridges and flats, allowing to actuate the plungers independently.
Selector switches are available in 2, 3, or 4-position versions, and are often used when more than one control option is needed. In general, the center position of the selector switch is the starting cam position. Left position presses the left plunger in the selector switch. Turning the selector switch to the right presses down the right plunger.
Selector switches use cams in combination with contact blocks to provide a wide range of circuit openings and/or closings. In the following diagram, "X" designates a closed circuit (energized or "on") for a particular selector switch position, and "O" to designate an open circuit (not energized or "off").
In the figures below, a 3-position selector switch is used to open or close two circuits, "hand" and "auto", for a pump application. It works in the following manner (reflects a left, center and right selector switch positions).
Indicating lights are part of selector switches. Setting a selector switch is how we tell machines how to operate. Indicating lights tell us what the machine is do or failing to do. When a light is connected to a machine process, and the light is on, the machine shows that it's working.
Selector switches are used when more than one control option is needed (e.g. Hand-Off-Auto). These switches are preferred when a maintained contact is needed.
Contact blocks are an integral part of selector switches. The contact block can have normally open (NO) and/or normally closed (NC) configurations. Single circuits contain a contact block of either one normally open or one normally closed circuit. For applications that need only one contact, a single circuit is an efficient, inexpensive way to get the job done. Dual circuits offer two contacts in a single contact block. The combinations include:
- 1 normally open and 1 normally closed contact
- 2 normally open contacts
- 2 normally closed contacts
- Combinations with special delayed opening or early closing contacts
Selector switches are available in a variety of styles including
illuminated, non-illuminated, and non-illuminated key operated. Styles offered range from maintained or spring return, incandescent or LED, and 3-50 amps. Work with a selector switch specialist to determine the best product for your application.