Switches

Switches

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Switches

  • Similar to pushbuttons, switches open or close a circuit
  • Pushbuttons are momentary switches because they close (complete) a circuit only while the button is pressed
  • We are going to look at maintained switches that continue to close or open a circuit indefinitely
  • We will typically just call these components “switches”

Terminology

  • Poles: The number of distinct circuits that can be controlled by using the switch
    • e.g. “single pole” (SP) or “double pole” (DP)
  • Throws: The number of positions the switch allows the circuit to connect to
    • e.g. “single throw” (ST) or “double throw” (DT)

Poles and Throws Explained

SPST - Single Pole, Single Throw

  • There is one single circuit (single pole)
  • The input 1P is either connected to output 1T or to nothing (single throw)
  • Notice there there are two connectors on the switch (input and output)

Poles and Throws Explained

SPDT - Single Pole, Double Throw (This is what you have in your kit)

https://cdn.sparkfun.com/assets/2/7/c/c/c/517edaface395f581d000001.png

  • There is one single circuit (single pole)
  • The input (1P) is either connected to output 1T or output 2T (double throw)
  • Notice there there are three connectors on the switch (1 input and 2 output)

Poles and Throws Explained

DPDT - Double Pole, Double Throw

https://cdn.sparkfun.com/assets/6/e/d/9/0/517edbabce395fd51d000000.png

  • There are two circuit (double pole)
  • Input 1P is either connected to output 1T or output 2T (double throw)
  • Input 2P is either connected to output 1T or output 2T (double throw)
  • Notice there there are six connectors on the switch (2 input and 4 output)

SPDT - Single Pole, Double Throw

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Exercise

  1. Connect switch to 3.3v, A5, and gnd
  2. Use serial monitor to read and display switch value

Credit

  • Sparkfun has some great illustrations on this for a deep dive into switches
  • Images created with Fritzing

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