In autumn 2018, I was making a sound installation where I needed a system that keeps microphone closed as long as no-one is near it. Only when a visitor walks in front of the mic the line should be opened automatically. Inspired by Optogate, I decided to go for a distance-based mute switch. However, instead of purchasing a commercial solution I thought that why not build a version of my own!
My device uses a Time-of-Flight (ToF) sensor to detect the proximity. Since ToF sensor is based on infrared laser, and the gadget turned out to look quite retro, I named it futuristically Lasergate 2000. An Arduino-compatible board reads the sensor and operates a relay that connects/disconnects the microphone signal as well as controls the indication LED's (that can be switched off in an installation setup).
The Lasergate 2000 turned out to work surprisingly well with normal dynamic and condenser microphones. However, when plugging it into a wireless transmitter (Sennheiser SKP 100 G3), it induced a loud rhythmic interference to the signal. So something to work on still! Also, unlike Optogate, my gadget doesn't run on phantom power, but instead with a 9V battery. Perhaps next model...
This was a nice project to design and build. Since a device like this may be useful for others, too, I thought it may be cool to share it with you even after some years. You'll find the circuit diagram and Arduino sketches here on my github. Feel free to use them for your own purposes. However, if you come up with any improvements, please let me know!