Machine Design

DIP rotary switches

It is no secret that numerous functions once handled with circuitry are migrating to software.

The trend has given a larger role. These devices are used to generate binary or hexadecimal logic signals that depend on the switch position. They serve as a means of providing information to software about settings, preferences, or other userspecified parameters.

The switches typically have four output pins which generate binary patterns for either decimal 0 through 9 or hexadecimal 0 through F. Their moving component is a plastic rotor which turns in the plastic switch body. On the under side of the rotor are cam lobes that force movable contacts down onto fixed contacts at each stop position. This cam action prevents logic errors that might otherwise be caused by dragging of the movable contacts on the fixed contacts.

Molded onto the top of the rotor are peaks and valleys. A corrugated circular spring rides over these peaks and valleys. The high points of the corrugated spring drop into the valleys of the rotor and provide positive tactile feel and stops at each switch position.

Modern switches are assembled with fully automated methods. The molding-in of fixed contacts allows for extremely low profiles that permit close stacking of PC boards.

Electrical switching capacity of these devices is typically 100 mA at 5 Vdc, and the nonswitching rating is 100 mA at 50 Vdc. Recently released devices also are heat resistant and compatible with lead-free solder directives.

NKK Switches provided information for this article, www.nkkswitches.com.

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