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So a few years back, my teacher had this toy chick, that had two contacts on the bottom. When you touched both, it chirped. Whn you touched one, and you touched a friend who touched the other, it chirped. So if electricity can run through you like that, why cant the same thing work with a battery and something that takes that battery? (leave the +side in, touching the - side, and then touching the contact for the - side)

## 6 Replies

lemonie (author)2007-03-26

The toy would have had a battery, but the current flow (through flesh) would have been very low. Perhaps there was a capacitor discharge involved somewhere? I'm not quite sure what you're asking in your last question, could you expand? L

Weissensteinburg (author)2007-03-26

I was pretty much just asking why it doesnt work to have electricity from a battery flow through you to the battery contact.

lemonie (author)2007-03-27

It does work, but you wouln't notice it (low curent). However, if you'd like to put your tongue across the terminals of a 9v battery you would (classic for school-kids)

LasVegas (author)2007-03-27

The chick audio circuit was triggered by your body's capacitance, not conductance. Any change in the capacitance between the contact point would trigger the chirp circuit. You can find all sorts of capacitance triggered circuits on the net. Try Google.

Weissensteinburg (author)2007-03-27

Ohh, alright, thanks for explaining that.

opqdan (author)2007-03-26

The body has way too much resistance (500K-2M Ohms) to be able to power anything from a battery using you as a wire.

I imagine the device uses a simple Op Amp comparator to compare to ground and cause the chirp off of the reference voltage.

For example, take this simple comparator, connect V2 to ground and V1 to the + battery with the open circuit in between. When ANY voltage greater than Vref (0 in this case) comes into V1, Vout will jump up the maximum supplied voltage (I suppose -V in this case, although you could easily make it +V) without having to actually pass through the bodies.

Disclaimer: I am not an electrical engineer (but I am a computer engineer) and I haven't dealt with op amps since freshman year of college. I make no guarantees that this will work, but the concepts should be mostly correct.