Cam-action switches

Aug. 4, 2005
Cam-action switches are often candidates for uses where several moderate to high-current connections must switch in various configurations with one turn of a knob.

are often candidates for uses where several moderate to high-current connections must switch in various configurations with one turn of a knob. These switches are high-volume industrial devices generally constructed in sections or decks, each of which contain one or more sets of contacts (poles). Manufacturers can gang decks together as necessary to get the right number of contacts. The upper limit is about 12 decks.

The contacts sit on a spring-loaded cam follower. The cam follower rides on a specially configured cam. The cam is affixed on a shaft that connects to the front knob of the switch assembly. The shaft can be metal or plastic. Each cam also contains at least one notch. When the spring-loaded cam follower falls into the notch, the corresponding contacts close to complete the circuit. Otherwise, the cam holds the contacts open. Thus the cam controls the switching action, and it is possible to devise a number of switching scenarios through clever design of the cam profile.

also typically have a separate detent assembly that gives the switch tactile feedback and holds the switch in place at various rotation angles. The detent mechanism ensures that the switch holds its position even if there are no spring-loaded contacts in a detent at that particular point on the dial. Detent wheels typically provide 45°detents as standard as well as 30, 60, or 90° detenting as options. Detent assemblies also contain stop arms that limit the angular rotation to the desired number and location of positions.

Typical ratings for these switches are 24 A at 600 V with interrupt ratings of 3 A/125 Vdc or 20 A/600 Vac. Manufacturers also offer numerous options such as slip contacts for alarm and indicator circuits, pull-to-lock handles for safety lockout, lighted switches, indicator LEDs, and various connection styles.

Electroswitch Corp. ( information for this article.

About the Author

Robert Repas

Robert serves as Associate Editor - 6 years of service. B.S. Electrical Engineering, Cleveland State University.

Work experience: 18 years teaching electronics, industrial controls, and instrumentation systems at the Nord Advanced Technologies Center, Lorain County Community College. 5 years designing control systems for industrial and agricultural equipment. Primary editor for electrical and motion control.

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