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I intend to buy CH340G USB Microcontroller Board Arduino UNO R3 ATmega328P Development Module

I want to use it and a MOSFET or whatever needed to act as a button for a TRRS wire I already have home made to act as a call button. I know it has to be 0ohm when activated but im not sure if this can be done and with what and how.

I was hoping to have a key on my computer activate the code from the arduino which I dont mind figuring out later but I just need to get an idea on what to use for the button and how I would activate it after wiring.

Andrew Gravlin
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  • most (all?) MOSFETs have a diode across source to drain, so that won't work very well with an AC signal like music. You could use a reed relay. The only other non-polar switch i know if is a CDS, but those might have too high a resistance here. – dandavis Jun 04 '20 at 20:01
  • Its not being used for music just to activate like if I took a standard momentary push button from mic to gnd on the TRRS plug. But I wanna do it from Arduino so I can control it on hotkey or mouse button. – Andrew Gravlin Jun 04 '20 at 20:06
  • you could likely use an nchan fet wired source to gnd, drain to the other side of the button, whatever that's connected to. – dandavis Jun 04 '20 at 20:08
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    Better to use an opto isolator or a small reed relay to keep everything isolated. – Majenko Jun 04 '20 at 20:09
  • If you are trying to answer phone calls, bear in mind that the ring signal is something like 90VAC. (For historical reasons it is enough voltage and current tp ring an electromechanical bell. I've gotten a pretty unpleasant shock before when I was working on phone wiring when a call came in.

    That's a problem for 2 reasons: It's too much voltage for all CMOS circuits and most transistors, and transistors can't switch AC. You should isolate the TRRS pins from your digital circuitry, and use a "digital" relay to close the circuit.

     – Duncan C Jun 04 '20 at 20:13
  • DuncanC: This is for a Cell Phone TRRS 3.5mm Audio cable. I dont think its rated that high..

    @Majenko: That actually looks like a neat idea. I just need to figure out how that works with a switch that should be off to start.

     – Andrew Gravlin Jun 04 '20 at 21:05
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    a reed relay has normally open contacts – jsotola Jun 04 '20 at 22:53
  • For this a reed relay would be my ideal choice. When you're working with audio signals adding anything in there that's not 100% passive could corrupt the audio signal. – Majenko Jun 05 '20 at 08:55

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