Switches - Naval Sea Systems Command

[Pages:12]Switches

Introduction

Switches are available over a large range of different sizes, packaging styles, and quality levels. They range from miniature pushbuttons to large power conductors. In fact, so many switch styles are available it is often difficult to select the most appropriate.

Like relays, switches contain moving parts. This makes them sensitive to wearout failure mechanisms. Moving parts also cause switches to have relatively high failure rates, although these high failure rates are often due to misapplication of the part rather than inherent problems with the switch itself. Switch selection often does not receive sufficient attention during the design or parts selection process because switches are not considered high priority items.

This is intended to be a guide to aid the designer in the selection of an appropriate switch for the intended application. More detailed information is available from vendors and MIL-STD-1132, Selection and Use of Switches and Associated Hardware. A further source of information and complete listings of all military specifications are available from DSCC (Defense Supply Center Columbus) 3990 E. Broad St., Columbus, Ohio, 43216-5000.

Packaging

Switches are available in a variety of package styles, especially among the commercial types. Many are unique to particular applications e.g., pushbuttons, momentary tact, thumbwheel, lever types, slide switches, rocker, key (or switchlock), toggle, rotary, DIP switches, among others. In addition, keypads and keyboards are also considered switches. It is beyond the scope of this document to give a detailed description of every switch type; Tables 1 and Figure 1 give an overview of switch types.

Figure 1. Factors Affecting the Selection of Switches

Table 1. Military Switch Styles and Applications

Switch Type

Switch, Push-Button, Illuminated

MIL-SPEC MIL-S-22885

Switches and Switch

MIL-S-8805

Assemblies, Sensitive and

Push (Snap Action)

Switches, Multi-Station, push-button (Illuminated and Non-Illuminated

Switches, Pressure

MIL-S-24317 MIL-S-9395

Switches, Rotary

MIL-S-3786

Switches, Rotary Selector Power

Switches, Rotary (Printed Circuit), (Thumbwheel, Inline, and push-button)

MIL-S-6807 MIL-S-22710

Switches, Thermostatic (Metallic and Bimetallic)

MIL-S-24236

Switches, Thermostatic (Volatile Liquid), Hermetically Sealed

Switches, Toggle Environmentally Sealed

Switches, Toggle, Positive Break

MIL-S-28827 MIL-S-3950 MIL-S-8834

Switches, Air and Liquid Flow

Switches, Reed

MIL-S-28788 MIL-S-55433

Switches, Rotary, Snap Action

MIL-S-15291

Intended Application

Intended for panel displays and switching devices in AC and DC applications. Panel displays include various combinations of colors and legends.

Intended for AC and DC applications, where predetermined small and accurately controlled characteristics are required. Various means of actuating by toggle levers, push buttons, cams, and other light pressure devices. These switches have snap-action, which eliminates teasing.

Intended as panel displays and switching devices in AC and DC applications.

Intended primarily to detect changes in pressure, liquid and gas applications.

Intended primarily for low power, AC or DC switching applications (capable of making and breaking a resistive load of ................
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