WS2812B LED-strips are ran at 5V, and can consume up to 60mA per LED. This can quickly add up to a few amperes.

Image of WS2812B LED strip

Would I receive a chock if I'd touch the connections between each LED while the strip is powered up? I'd guess so, since the current flows between the points -- however I've seen videos of people touching the strip while powered up.

Is it safe to touch the connection points while the strip is powered up?

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    \$\begingroup\$ With your tongue, yes. Otherwise, not likely. youtube.com/watch?v=hp97GjuULX8 and youtube.com/watch?v=XDf2nhfxVzg \$\endgroup\$ – Fizz Oct 26 '15 at 10:41
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    \$\begingroup\$ Very very very unlikely, because the 5V that you will touch together with the 1Meg resistance of your fingers will result in I = U/R = 5/1meg= 5 uA. Not harmfull in any way! \$\endgroup\$ – Weaverworm Oct 26 '15 at 10:54
  • \$\begingroup\$ The current in the LED circuit is irrelevant. The circuit that you would feel a shock from involves your skin and body. Dry skin has a high resistance, ohms law applies I=V/R Not many V's lots of R's = very low I's \$\endgroup\$ – Icy Oct 26 '15 at 10:56
  • \$\begingroup\$ @Weaverworm. Resistance of skin is between 5-100 Kohm. What you say is in dirty and oily skin. \$\endgroup\$ – HOPE Oct 26 '15 at 10:59
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    \$\begingroup\$ @Weaverworm.See this : ncbi.nlm.nih.gov/pmc/articles/PMC2763825 . It says : A calloused, dry hand may have more than 100,000 Ω because of a thick outer layer of dead cells in the stratum corneum. The internal body resistance is about 300 Ω, being related to the wet, relatively salty tissues beneath the skin. Then I will come up to 100K, at last :) \$\endgroup\$ – HOPE Oct 26 '15 at 12:19

When your skin is sufficiently wet and clear of any oil or dirt, in best situation its resistance is about 3 K Ohm . When your supply is 5volt , assume you touch directly power pins. Current through your body will be :

I = V / R

I = 5.0 / 3K = 1.67 mA

If we refer to Wiki- Electricity Shock we can determine how much current in how much time cause damage to body.

enter image description here

As you see in case of this current you are always in green part of diagram.

If you touch your tongue, it's resistance will be hundred of ohms. then it's current will be tens of mA. According to this figure if you hold it for more than a second, it will cause you an AS-3 kind of damage, that it's not so serious indeed.

---Edited : According to our discussion in comments I prefer illustrate the Skin model here :

This is Anatomy of skin :

enter image description here

and it's equivalent circuit for this :

enter image description here

According to McAdams , there have been several observations of regional differences of skin impedance in the low-frequency range, which is dominated by Re. Therefore, variations of skin impedance between sites and subjects tend to be due to large variations of Re. Reference

Then as illustrated in this article too, skin resistance has imaginary and real part that in a DC situation only real part will be considered. In This situations skin resistance will vary depending on lots of conditions but at last it will vary from 100K to 500 Ohm in different situations for a normal skin without dirt.

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  • \$\begingroup\$ I'm not sure how relevant that diagram is since he's asking about DC. \$\endgroup\$ – Fizz Oct 26 '15 at 11:19
  • \$\begingroup\$ @RespawnedFluff : If you read the article, it say an AC current harm more than a DC one. DC current sides effect is between 2 to 10 times less than a AC current according to mentioned source. Then I attach a high risky diagram that was included in article, since it cover DC current stimulus also. \$\endgroup\$ – HOPE Oct 26 '15 at 11:25
  • \$\begingroup\$ I also think you've used the dry skin condition as 3K but incorrectly labelled as wet. For wet it's about 500 ohms. See page 5 in bme.ccny.cuny.edu/faculty/mbikson/BiksonMSafeVoltageReview.pdf \$\endgroup\$ – Fizz Oct 26 '15 at 12:18
  • \$\begingroup\$ @RespawnedFluff. I refered to ncbi.nlm.nih.gov/pmc/articles/PMC2763825 . It says a dry skin is 100K and internal part of body is 500R. Through practical sitations that we study in neurology it's stated that for electrode placement on a skin in best situation we can reach 1K to 3k of resistance. \$\endgroup\$ – HOPE Oct 26 '15 at 12:21
  • \$\begingroup\$ Probably because electrode area is small in neurology. I've read that TENS machines are designed for 500 ohm loads... can't remember where right now. \$\endgroup\$ – Fizz Oct 26 '15 at 12:25

Short answer: it's fine to touch them.

Longer answer:

Roughtly speaking the current through the body depends on three things. The open circuit voltage of the power supply. The source impedance of the power supply and the impedance of the human body.

The impedance of the human body varies a lot depending on contact area, presense of moisture on the skin etc and this makes it difficult to have hard and fast rules on what is safe but the general rule of thumb is that 50V is about the point where you need to start seriously worrying about electric shock risk. 5V is an order of magnitude lower than that.

A lot of people seem to think that high current supplies are more of a shock risk than low current ones. This is true if we are talking about extremely low current supplies but there is going to be negligable difference in tissue current between touching a 5V 100ma supply and a 5V 100A supply. In both cases the source impedance of the supply will be negligable in comparision to the impedance of the body.

Having said that while high current 5V supplies aren't a shock risk under normal conditions they can be a fire and burn risk. IIRC people have had serious burns when jewlery has shorted out high current supplies. If you are deploying large numbers of these LEDs I would suggest splitting their power supply into groups with each group fused at no more than a few amps.

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