Pushwheel switches are operated by a rotating wheel or dual buttons and are activated by a rotating shaft with several stop positions. They are made of thermoplastic or metallic materials and are available in standard, miniature and subminiature sizes. Some pushwheel switches are mounted on printed circuit boards (PCBs) in order to control the behavior of electronic devices. Changing the position of the rotating shaft generates a circuit code in binary, octal, or hexadecimal format. Binary coded decimal (BCD) circuit codes represent each decimal digit with a four-bit binary number. Octal systems represent quantities with eight digits: 0, 1, 2, 3, 4, 5, 6 and 7. Hexadecimal systems represent quantities with 16 symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F. Binary, octal, and hexadecimal complements are also available. Some pushwheel switches use Gray code, a non-arithmetic circuit code that does not assign specific weights to bit positions.
Pushwheel switches rotate continuously or stop between positions. Performance specifications include maximum current rating, maximum AC voltage rating, maximum DC voltage rating, and maximum mechanical life. Terminal type defines the electrical connection. Insulated wire leads are permanently attached to pushwheel switches. By contrast, solder terminals are semi-permanent while screw terminals are temporary. Other terminal types for pushwheel switches include quick-connect blades and plugs; straight, right-angle, and side pins; and surface mount technology (SMT). Unlike other mounting methods, SMT adds components to a PCB by soldering component leads or terminals to the top surface of the board. Surface mounted components are usually smaller than equivalent through-hole leaded devices and, in some cases, are also less expensive.
Special Features and Applications
Pushwheel switches offer a variety of special features and can be used in numerous applications. Some devices have imprinted indicators such as ON/OFF or HI/LOW. Others include audible indicators for position intervals and self-cleaning features to reduce mechanical wear. Many pushwheel switches are listed with Underwriters Laboratories (UL), certified by the Canadian Standards Association (CSA), or feature the European Union’s CE Mark. Dustproof, weather-resistant, and waterproof models are commonly available. Applications for pushwheel switches include navigation and communication equipment for the avionics industry, precision measurement equipment, gaging, test and measuring equipment, commercial sound mixing, military voice and data communications, radios, and transmitters and receivers.