Wednesday 29 March 2017

switches - Integrating momentary switch with a Raspberry Pi


Please note: Although my question involves a Raspberry Pi, this is a pure electronics question at heart.




I'm trying to figure out how I can wire this illuminated momentary switch to my Raspberry Pi 1 Model A (hereafter RPi) such that:



  • The switch is normally open


  • When pushed down: it closes the circuit, lights up and fires a HIGH signal to a GPIO input pin (GPIO 04 in my case)

  • If needed, I can make the GPIO 07 pin an output pin and make it available to help run the light/LED inside the switch, but not sure if that's needed


I will be setting the RPi's internal resistor on this pin, so I don't think I need a resistor for the switch, but I believe I still need one for the switch's LED/light (please confirm!). I will also be working out a "debouncing algorithm" at the software layer if needed.


But I'm stuck trying to figure out how to wire the dang thing to my RPi:


enter image description here


According to page 15 of that switch's datasheet:


enter image description here


So I'm not sure:




  • What GPIO 04 on the RPi is supposed to connect to on the switch; and

  • What I'm supposed to do with Pins 1 and 2 on the switch; and

  • What I'm supposed to do with Pins X1 and X2 on the switch; and

  • What I'm supposed to wire GPIO 07 up to (if anything)


Can anyone nudge me in the right direction here?



Answer



From page 16:



• A current-limiting resistor is built into the LED Lamp, so external resistance is not required.




You have the A22NZ-BNM-TWA model, so 6VDC is needed.


enter image description here


I'm assuming that since you are using this button you have 6VDC available. Since you can't drive 6VDC and any significant current with the RPis GPIO, you could do the following:


schematic


simulate this circuit – Schematic created using CircuitLab


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