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This could sound ridiculous to someone with an ounce of experience, but I'm just getting started, so here we go ;) Full question is 3 parts...

First, what is the lowest amperage needed to light an LED? I think there are blue LEDs that can light up at 5 mA. 10 mA is where shocks begin to get painful.

Second, in a circuit with a battery, is there any scenario where that low voltage of a battery could deliver a painful or harmful shock if something went wrong?

Third, could you power that LED with a bare copper wire touching your skin, such as wire jewelry, or would that circuit short on your skin or provide an electric shock?

Simply, I'm trying to figure out if it's possible to wear a bare copper wire around your neck or wrist that powers an LED, or does that wire need to be insulated?

My instinct is to say no, but I'm also thinking maybe your skin would provide enough resistance to both prevent shock and force the current to continue down the wire.

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First, what is the lowest amperage needed to light an LED? I think there are blue LEDs that can light up at 5 mA. 10 mA is where shocks begin to get painful.

This is roughly correct. However it's very easy to design a circuit that can deliver 5 mA to an LED but wouldn't be able to deliver more than a couple microamps to a human body, because of the much higher resistance of a body.

in a circuit with a battery, is there any scenario where that low voltage of a battery could deliver a painful or harmful shock if something went wrong?

For a ~1.5 V battery, it's pretty difficult to detect them in my experience.

As a kid, we used to test 9 V batteries by touching the two terminals to our tongues. It gives a pretty noticeable tingle. It might be dangerous for somebody with a heart condition or an implanted medical device.

could you power that LED with a bare copper wire touching your skin, such as wire jewelry, or would that circuit short on your skin or provide an electric shock?

If you are not "at risk" (i.e., heart condition or implanted medical device) this will probably work fine.

You would need to separate the "to" and "from" wires from each other so they don't short to each other.

I'm trying to figure out of it's possible to wear a bare copper wire around your neck or wrist that powers an LED, or does that wire need to be insulated?

FWIW, there are kinds of insulation that almost look like they're not there. Clear varnish or clear plastic. These might be more practical for a wearable application.

Also remember that copper can stain your skin in some circumstances. This is probably more likely if you sweat while wearing it. Of course this applies to any copper jewelry, and isn't related to whether you are using the copper in an electric circuit.

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  • \$\begingroup\$ Yeah, I just edited because it occurred to me about the resistance (last line of post). It also occurred to me there might be a suitable coating or that I could encase a very thin insulated wire in thin decorative metal "beads". But the science of it was still worth asking about so the response is appreciated :) I couldn't understand why people making LED pendants always had ugly plastic coated "chains" and it's all cheap toy looking. So much potential for wearable LED jewelry if made with some class. \$\endgroup\$ – Path Sep 7 at 3:00
  • \$\begingroup\$ If wearable jewelry is what you want - some of the reflective / luminous stuff as the massive advantage of not needing a power supply... \$\endgroup\$ – Solar Mike Sep 7 at 3:55
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Any working voltage below 60V is considered ‘touch safe’, that is, it’s low enough that it poses almost no shock hazard. (60V will be an uncomfortable tingle, but not enough to hurt you.)

LEDs will light at voltages much lower than that, between 1.7 to 3.5V or so depending on the color. Using, say, a 3V battery for power poses no shock risk and could be worn safely.

Notice I haven’t mentioned current yet. Why? Because current by itself isn’t the actual hazard for shock. Something has to push that current, which is voltage.

LEDs can light on very low currents. A small LED typically will take 2-10mA to make useable brightness - this value again depends on color and LED type.

On the other hand the the body has relatively high resistance compared to an LED, so the low voltage used for an LED drive couldn’t put any more than tens of micro amps into your body, even if you touch two fingers directly across it.

So, low current, very low voltage. Quite safe, really.

Except...

Now, there is a hazard to consider: a wiring short. A thin wire shorted across the battery can heat up and burn, even with a smallish battery like an alkaline AA. You will want to prevent that by insulating the bare wire to prevent shorting out. A lacquer coating can do that, or even better use ‘magnet wire’ which has clear insulation to make your pieces.

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  • \$\begingroup\$ The burn risk is serious. If a short does occur and the battery can supply enough current to make the wire very hot it will burn through the skin. I did it myself holding a wire between my thumb and finger. Doing it around a person's neck could leave a permanent scar. \$\endgroup\$ – Transistor Sep 7 at 9:16
  • \$\begingroup\$ The heat can be prevented with a 10 mA fuse. The fuse couldn't stop a sudden shock, but heat it can stop. \$\endgroup\$ – Path Sep 8 at 7:47

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