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Is there some reasonable means by which to detect activity in a circuit using a Raspberry Pi?

For example, say some device has a buzzer that goes off when it's done doing what it's doing and I want to detect this buzzer going off and then use software on the RasPi to send a text or an email. The software part I can handle but I have no clue how I would go about detecting the buzzer, I'm assuming there's a circuit inside the device that activates when the buzzer goes off and if I could physically locate this I could add some of my own hardware to the circuit for detection but I'm a software guy not an EE so I'm not really sure where to start.

Any ideas? Help would be greatly appreciated.

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  • I'd start by looking through copies of the Magpi to find projects which look similar.
    – joan
    Commented Jul 29, 2016 at 14:21

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This could be done. You can use any number of 'hardware' devices to monitor the circuit. One could use an audio detector like: https://www.sparkfun.com/products/12642 , however on a rpi you would need to step down the input voltage... actually not a bad idea. With this chip you could find the amplitude of the buzzer from precisely where this chip is located, and once the amplitude exceeds the "normal" range, send a text. That's the route I would take.

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  • "With this chip you could find the amplitude of the buzzer..." -> Not via the pi you can't. That's explicitly an analog aspect of the sensor, and the pi has no analog inputs. All you could do is detect the presence/absence of sound via the digital output, and something arbitrary along the same lines if you connected the analog output to one of the pi's digital GPIOs. Unless you mean exploiting the fact that "gain can be adjusted with a through-hole resistor, to change the threshold of the binary (gate) output pin" (which there's no explanation of here).
    – goldilocks ♦
    Commented Aug 2, 2016 at 14:51
  • That's correct. Thanks for pointing that out. I still think that's the route I would take, unless you have a better idea?
    – Jakob Vendegna
    Commented Aug 2, 2016 at 16:20
  • No, although using an ADC or an audio sensor with one built in might be easier and more flexible than the resistor method (I imagine there are some I2C based options around). Except the OP does mention the opportunity to hack the buzzer electronics directly, which would be more bulletproof -- but there isn't enough information to say much about that and it is probably something more suited to Electrical Engineering.
    – goldilocks ♦
    Commented Aug 2, 2016 at 17:28
  • Or use my trick of setting up the Pi with a serial connection to an Arduino Nano that can handle the sensing. I set up the Arduino IDE on the Pi and access it remotely via RDP/WiFi. Pi/Nano make a great pair. Communicating via serial is trivial, and it allows the IDE programmer to work without moving any wires. Just use the regular Arduino Nano programming cable and it shows up as /dev/ttyUSB0 on the Rpi.
    – SDsolar
    Commented Apr 2, 2017 at 21:44

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