Question

I need a contact closure for each position of my 3 position selector switch. How can I get that with the two Normally Open and two Normally Closed contacts you supply?

Answer

Most three position selector switches only activate contacts to either side, LEFT or RIGHT, and the CENTER position does not make any contacts change state. This is the case with all the brands of three position selection switches we sell. Sometimes a customer wants to have a contact for all three positions, though, LEFT, CENTER, and RIGHT positions. The traditional method of making this happen is to have four total contacts, two Normally Open (N.O.) contacts and two Normally Closed (N.C.) contacts. You mount one N.O. Contact on each side and one N.C. contact on each side. The N.O. contacts close when the knob or level is pushed to the LEFT or RIGHT side where the associated N.O. contact is and that N.O. contact will close. That satisfies the requirement for a contact for the LEFT and RIGHT positions.

To get a contact for the CENTER position, you wire the two N.C. contacts in series and use the two contacts wired in series as a single contact for the CENTER position. If the knob or lever is in either the LEFT or RIGHT position, the N.C. contact for that side will be open, so there will be no current path between the two contacts wired in series. If the knob is in the CENTER position, however, both N.C. contacts will be closed so there is a current path through the two N.C. contacts wired in series, so you have a closed contact for the CENTER position. Note this wiring scheme works regardless of whether you have four discrete contact blocks, or two combo blocks that have one N.C. and one N.O. contact per block, like our E22 series of switches have.

	Left Side Contacts			Right Side Contacts
Selector position	NO Contact	NC Contact		NC Contact	NO Contact
Left	C	O		O	O
Center	O	C		C	O
Right	O	O		O	C

C = Contact is closed
O = Contact is open

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FAQ Subcategory: None

This item was last updated on 2021-03-02
Document ID: 1378

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