Controlling a TENS with an Arduino

[Miner]

Does anyone have any experience controlling a TENS unit with an Arduino? What about simply cutting one of the wires and inserting a relay to turn the voltage on and off? Or maybe two relays in series for safety just in case the contacts stick? Of course they would be normally open relays to accommodate power failures. Any thoughts?

[sweh]

Check out Simone Giertz... https://www.youtube.com/watch?v=nQLFesz9O1g

[ruru67]

Yep, that works. I've used really small relays to switch TENS leads on & off, as these can run directly from the Arduino without a driver circuit (you do need a flyback diode though). The duty cycle on relays small enough to be directly driven isn't great. But adding a simple NPN driver is pretty easy too - or buy a relay module that just takes +5V power, ground and a signal line, and wire it directly to your Arduino.

Relays do isolate your hardware from the nasty voltages you'll find in the TENS unit. You only need to switch one side of each channel, assuming it's a genuine, fully isolated, two-channel machine (and bot just a single channel with two leads on each channel).