[Noisebridge-discuss] how much current can you put through skin (comfortably)?

[Rachel McConnell]

Are you planning to use the skin to complete a circuit, or just so that
the jewelry 'knows' it's being worn so it can turn itself on?  If the
latter, you might be able to use a capacitance sensor, which is what
touch screens & so forth use and is entirely non-dangerous.  It even
works through small amounts of glass, plastic, fur, etc -- basically
anything non-conductive.  I've done some work in the past with a QProx
chip, which was very easy to work with.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=427-1138-1-ND

If I ever showed you my orange/black stripy purring thing (it vibrates
when you pet it), I used that chip in it.

Rachel

Mikolaj Habryn wrote:
> We did some experiments on this at sensebridge -
> https://www.noisebridge.net/wiki/NBC_2009August2 - and from memory,
> our rough conclusions were:
> 
> DC is bad news - common theme was feeling nothing as voltage was
> gradually turned up, and then having a small sensation that rapidly
> escalated into significant pain without needing the voltage to
> increase - theory goes that once it starts to hurt, your skin does
> something (like sweat) which improves conductivity and it hurts more -
> lather, rinse, repeat.
> 
> AC is interesting - 1mA seems to be a good upper bound for current,
> and we experimented with a voltage range of about 5 - 20 (don't recall
> if that's RMS or peak, though). If you make a current source that's
> capped at 0.5mA or so, without being able to go above 15V, I'd imagine
> you'd get good results.
> 
> m.
> 
> On Wed, Jan 6, 2010 at 1:15 PM, Joel Jaeggli <joelja at bogus.com> wrote:
>> As little as 50ma can stop your heart, but I don't imagine you're
>> planning on using your trunk section to complete the circuit or as a
>> path to ground. of course that also presupposes enough voltage to drive
>> it which is why we distinguish between high and low voltage.
>>
>> There are components for making switches for this purpose rather than
>> just using your finger to complete the circuit...
>>
>> http://en.wikipedia.org/wiki/Touch_switch
>>
>> meredith scheff wrote:
>>> I want to make some jewlery with embeded circuits where they activate
>>> with touch..but how much can i put through skin and have it be, well, OK?
>>> mer
>>>
>>> --
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>>> David Thoreau
>>>
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