Rotary Switches

Rotary switches move in a circle and can stop in several positions. There are two basic styles: single-deck and multi-deck. Both types of rotary switches can be actuated with a bare or knobbed shaft, a flush actuator, or a key. Angle between positions, mechanical life, number of poles, number of decks, and number of poles per deck are important physical switch specifications to consider. Measured in degrees, the angular distance between positions determines the number of switch positions. For example, a 4-position rotary switch has a 90° angle of throw. For a 100-position rotary switch, the angle of throw is 3.6° degrees. Mechanical life represents the maximum life expectancy for rotary switches. The number of poles is the number of separate circuits that can be activated at any given time. The number of decks is the maximum number of decks that can be attached to a common, actuated shaft. The number of poles per deck is the number of separate circuits that can be activated through a rotary switch per deck.  

Rotary switches are usually made of plastic or metallic materials. Parameters include stop style, contact style, and actuator features. Rotary switches with an adjustable or continuous stop are commonly available. There are two basic contact styles for rotary switches: shorting and non-shorting. Shorting or make-before-break switches prevent arcing during position changing since the next position is connected before the previous position is disconnected. Non-shorting or break-before-make switches open the preceding circuit before closing the next. Some rotary switches use actuator detents, mechanisms that hold the switch in a given position after the actuating force is removed. Others use a potentiometer. Tease-proof mechanisms prevent a rotary switch from staying between positions after force is removed. Rotary switches with a guarded position require a special action, such as pushing or pulling the shaft, in order to change switch position. Keylocking toggles are used to prevent unauthorized personnel from accidentally shutting off the power, or tampering with the switching or the branch circuit load. 

Terminal type, approvals, and features are additional parameters for rotary switches. PCB pins, screw terminals, solder terminals, and wire leads are common terminal types. The European Union, Canadian Standards Association (CSA), and Underwriters Laboratories (UL) usually provide approvals and certifications. In terms of features, some rotary switches are dustproof or include self-cleaning wiping contacts. Others can be configured to provide binary coded decimal (BCD) or octal outputs. Rotary switches with a momentary-on feature can maintain a position during positive loading or actuating.

• Rotary Switches
  Available in configurations up to four throw, illuminated/non-illuminated, 10A and 20A. Compact, with a very positive detent action, and snap-on knobs. Sealed to IP-53 for protection against dust and...
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• 50-Amp Rotary Switch for Forward/Reverse Applications
  Responding to demand, Cole Hersee now offers a 50A DPDT switch with heavy duty components that deliver continued reliability. Constructed with heavy gauge (3/32" thick) terminals and silver-laminated...
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• Making Switches Watertight on Water-Resistant-Failsafe Ohmmeters/Digital Ignition Testers
  Situation: AMPTEC RESEARCH of Austin, Texas manufactures safety ordnance test instrumentation for missile rocket motors, detonators and warheads for the U.S. aerospace industry. The U.S. Navy wanted a...
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Part Numbers for Rotary Switches