Safety levels for passing electricity through humans


I would like to build a circuit that controls a switch. To turn the switch on I want it to require a minimum of two people holding hands and touching a terminal each (potentially some sort of handle), the charge should pass through them to complete the circuit.

What are the voltage/current levels that I would require to make the circuit work well but be 100% safe. 5v? 12v? Can you advise me on other safety issues I need to consider.


by Kilmo
December 11, 2019

2 Answers

Answer by Foxx

I did some work on this many years ago while working on a masters degree in electrical engineering. We found that the things you're asking vary all over the map from person to person, from time to time for the same person and with the current path. We found that a very very general rule is that some people, by no means all, can feel 1 ma and most people, again by no means all consider 10 ma painful. We did not experiment further with this but I have read that 100 ma may be fatal depending on the current path. As for voltage, again, the voltage to cause any given current may vary all over the map because the skin resistance may vary from a few hundred ohms or less to 20000 ohms or more and in some people with dry, work hardened skin it can be 100000 ohms or more. I have investigated electrical accidents and I had one where a child was killed by 110 volts and another where a workman was not killed by a 110000 volt shock from a power transmission line although he did receive a bad burn. Based on my experience my advice is do not deliberately shock people as the risk of unintended consequences is too high.

+1 vote
by Foxx
December 11, 2019

Thanks Foxx. Good advice based on decent research by the sounds of it. I would never dream of using 110 volts! I was wondering if a 5v less than 1ma system would work. I have seen circuits that require a human touch on a terminal or sensor to make the circuit live (thinking modular synthesisers), these units are either 5 or 12 v, do you know how systems like that work? And could that be adapted to what I am trying to do? Or should I just scrap the idea!!? Ive seen it done before, but maybe they were being careless.

by Kilmo
December 11, 2019

Its capacity isnt it. Maybe I can build a system using an arduino that detects the electrical capacitance change that occurs from the human hand contact, but adjust the threshold to try to detect 2 humans worth?

by Kilmo
December 11, 2019

There's always the old schoolboy trick of charging up a capacitor to 100--200 volts then leave it on the workbench and wait for someone to pick it up.--- 5 or 12 volts will not normally cause a shock; we work with it all the time without a worry because our skin resistance is too high to allow any appreciable current to flow.

by Foxx
December 12, 2019

Answer by Kilmo

I’m not trying to shock anyone!!

+1 vote
by Kilmo
December 12, 2019

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