Como funcionam alguns tipos de chaves eletrônica
Autor: Flávio Fabrício Ventura de Melo Ferreira | Publicado: 2011-04-29T14:32:00-07:00

  Switches: A switch is an electromechanical device which is used to open  or close an electrical circuit. They are available in a number of  configurations. For now, we will only discuss a simple single pole  double throw switch (spdt). The number of 'poles' indicates how many  completely independent circuits are controlled by the switch. The number  of 'throws' indicates the number of positions that will result in an  electrical connection. The diagram below shows some of the internal  components of a spdt toggle switch. This is not a real switch, it is  only an example.                The switch below is a double pole double throw (DPDT)  slider switch. This switch has 2 independant circuits. The sliding  contact connects 2 of the 3 terminals for each half of the switch. The  position of the slider determines which 2 terminals are connected. This  diagram is a cut away view of the slide switch.      And this is the real thing.         This diagram is a cut away view of a normally open push button switch.      The real thing.      The demo below shows a system with multiple ways to control  the amplifiers and fan. The top amplifier is controlled solely by the  head unit's status (on or off). The head unit's remote output controls  the relay. The relay's output terminal (terminal 30 in this case) is  connected to the top amplifier's remote input. When the head unit is  turned on, the relay is energized and power is sent to the top amp's  remote turn-on terminal. When the relay is energized, power is also sent  to both of the toggle switches. If the toggle switch is in one  position, the amp or fan will be off. If the switch is in the opposite  position, the amp or fan will turn on/run. When the head unit is  switched off, the relay is switched off and everything goes off. To  toggle the switch position, click on either side of the handle.               Click HERE to make the demo fill this window.       This diagram shows the wiring for lighted rocker switches. The white wire is the supply wire from the  battery. It MUST  be fused at the battery. The proper fuse size is determined by the size  of the supply wire. For 14g use a 15 amp fuse. For 12g wire, use a 20  amp fuse. The individual fuses for each circuit should be the minimum  size possible. If the neon (or any other accessory) pulls 2 amps of  current, use a 3 amp fuse. If it pulls 3-4 amps, use a 5 amp fuse. There  is no advantage of using a fuse that's significantly larger than  necessary. This diagram may not be correct for all rocker switches.  Refer to your switch's wiring diagram for the correct wiring diagram.       In the following demo, you can open and close the switch.  For the normal connection, the internal lamp (could be an LED) lights  only when the external lamp is powered (when the switch is closed). For  the alternate connection, the internal lamp is always powered. The  external lamp is lit when the rocker switch is in the closed position.               Note: The lighted switches in the previous diagrams were SPST  models. I recently bought some lighted switches that could not be wired  as shown in the 'alternate connection' above. The switch was a modified  SPDT. This means that the power source would be connected to ground if  connected as in the 'alternate connection'. If you're unsure about your  switch, you can check it with an ohm meter. If you find that the  resistance between the center terminal and the ground terminal is near  zero ohms in either switch position, the switch is a SPDT and can be  wired only one way (light on only when load is connected to power).   Fonte:http://www.bcae1.com/switches.htm