How Selector Switches Work by GalcoIndustrial


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									                                      SELECTOR SWITCHES

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").

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
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 position).

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.

Dual circuit contact blocks save space in enclosures and add twice the functionality to a switch because
one switch operates two circuits. You can add multiple contact blocks to increase functionality. For
example, you can mount 4 dual circuit blocks to a 30mm pushbutton for a total of 8 circuits.

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

More information on Selector Switches can be found at the Galco Industrial Electronics Website

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