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This question already has an answer here:

According to various sources something as little as 0.01A = 10mA can be painful, at 0.1A = 100mA you can expierence *

  1. "ventricular fibrillation of the heart".
  2. "an uncoordinated twitching of the walls of the heart's ventricles which result in death".
  3. "As well as other painful things such as extreme breathing difficulties, Severe Shock, Muscular paralysis ...". *

How is that true? I've worked with an arduino and LEDs, LED Strips etc for quite a while yet never heard that 10mA can be painful let alone 50-100mA deadly.

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marked as duplicate by laptop2d, JRE, Harry Svensson, Bort, pipe Nov 4 '18 at 13:03

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  • \$\begingroup\$ the mentioned question is similar / same topic but still not similar enough to be called a dupplicate as my question revolves around micro-controllers and the dangers of mA while working with LED's / diodes etc... \$\endgroup\$ – StellarEquilibrium Oct 31 '18 at 19:19
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    \$\begingroup\$ Your microcontroller can't force enough current through your body to hurt you. Get an ohmmeter. Measure the resistance between your two hands. Use Ohm's law to calculate the current given 5volts and the measured resistance. \$\endgroup\$ – JRE Oct 31 '18 at 19:25
  • \$\begingroup\$ Your body is a resistor, and an Arduino does not have any voltages present that can cause that much current to flow in your body. I tried to dig out some hard numbers for you, and instead found that it'll take a LOT of digging (or one person who knows the applicable standard). As far as I can remember (and don't use this for design!) something around 60VDC is generally considered "safe", but I don't know if that applies if you're standing in salty water. 5V is safe as houses. \$\endgroup\$ – TimWescott Oct 31 '18 at 19:35
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First off, its voltage not current that kills (because you have to bypass the skin). The actual mechanism is current once you get under the skin.

The minimum current a human can feel depends on the current type (AC or DC) as well as frequency for AC. A person can feel at least 1 mA (rms) of AC at 60 Hz, while at least 5 mA for DC. At around 10 milliamperes, AC current passing through the arm of a 68-kilogram (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object.[11] This is known as the "let go threshold" and is a criterion for shock hazard in electrical regulations.

Source: https://en.wikipedia.org/wiki/Electrical_injury

Your not getting 10mA through your heart when you are playing around with electronics or low voltage <60V. Skin is more than 10k (as much as 100k), to get 10mA through 10k is at least 100V. If you have dry skin, it is much higher.

Per IEC directives Low voltage is lower than 50V

In the European Union, the Low Voltage Directive defines low voltage starting from 50 V AC, and 75 V DC. The directive only covers electrical equipment and not voltages appearing inside equipment or voltages in electrical components. IEC 60364 defines it as 50 V AC and 120 V DC.

Source: https://en.wikipedia.org/wiki/Extra-low_voltage

The body has resistance to current flow. More than 99% of the body's resistance to electric current flow is at the skin. Resistance is measured in ohms. 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. The skin resistance can be effectively bypassed if there is skin breakdown from high voltage, a cut, a deep abrasion, or immersion in water (Table ​(Table2).2). The skin acts like an electrical device such as a capacitor in that it allows more current to flow if a voltage is changing rapidly. A rapidly changing voltage will be applied to the palm and fingers of one's hand if it is holding a metal tool that suddenly touches a voltage source. This type of contact will give a much greater current amplitude in the body than would otherwise occur.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/

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  • \$\begingroup\$ +1; visualized in a nice video: Afrotechmods: "It's not the volts that kill you, it's the amps" \$\endgroup\$ – anrieff Oct 31 '18 at 20:05
  • \$\begingroup\$ I think I got it. So it depends on the voltage thus my experiments with µController components like LEDs, Diodes, motors are completely harmless since we are playing around with voltages <5V \$\endgroup\$ – StellarEquilibrium Nov 1 '18 at 12:55
  • \$\begingroup\$ Yep, voltages under 120V DC are considered safe. 5V is definitely safe. \$\endgroup\$ – laptop2d Nov 1 '18 at 14:40
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A circuit that is drawing 10mA or 50-100mA is quite a bit different than a circuit that could push that much current through you.

Figure out what the resistance of the human body is, then calculate how much voltage you would need to force that much current through that resistance. You will quickly see how your arduino is incapable of forcing even 1mA through your body.

Remember, just because something can source 10mA, doesn't mean that it can force that current into anything.

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  • \$\begingroup\$ the human body has a resistance ranging from 1kOhm (skin) to 100kOhm (heart) \$\endgroup\$ – StellarEquilibrium Oct 31 '18 at 19:39
  • \$\begingroup\$ @evildemonic "doesn't mean that it can force that current into anything" unless it is a charged inductor, that is... \$\endgroup\$ – Edgar Brown Oct 31 '18 at 19:44
  • \$\begingroup\$ @EdgarBrown Good point. In the case with a charged inductor we would have to see how high the voltage can get, and also see if the inductor can store enough energy to harm. You would need some way to quickly interrupt the current through the conductor, so the collapsing field raises the voltage, then connect this voltage across the body. Very much an edge case. \$\endgroup\$ – evildemonic Oct 31 '18 at 20:50
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    \$\begingroup\$ Not really. A flyback transformer (any transformer really) is just an "inductor with two coils" ;) Nobody said that you have to be grabbing the same set of wires that are charging the transformer. The core is what is holding the "charge." \$\endgroup\$ – Edgar Brown Oct 31 '18 at 20:55
  • \$\begingroup\$ Point taken. +1 \$\endgroup\$ – evildemonic Oct 31 '18 at 21:34
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To answer your question, you should be safe for most electronic work, but it is good safety practices to respect all electric circuits and take fundamental safety precautions.

The amount of current a person can handle depends upon many factors. Current quantity, current type, body mass, broken skin, path and length of contact time, etc.

Many similar charts exist. From Science online - Benefits and dangers of electricity

Electricity's Effects

The only scientific study I know of is Charles Dalziel, 1961 (Inventor of the GCFI). Ultimately, this is where the 100mA 60Hz AC and 500mA DC comes from.

Effect of current on human body

As can be seen from the chart DC levels are 3-5 times safer than 60Hz AC.

The first 5 rows are based upon human tests (check out pictures at end of report), while the last is estimated from experiments on dogs. It would be highly unethical to do these tests today.

Fibrillation (100mA-200mA) can be deadly because it sets the muscles of the heart pumping randomly requiring defibrillation as the only way to restart the heart. A higher current will cause serious injuries but the heart/lungs may start once the person is removed from the shock hazard.

Even currents as low as 16mA 60Hz AC and 76mA DC can cause unconsciousness and death if the exposure is long enough as the individual is frozen to the circuit. Your brain, hearts and lungs work, but you cannot let go. All of the muscles of your body are contracted. Think really, really good frozen tag.

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  • \$\begingroup\$ I'm gasterflaterd.I don't understand, I always worked with arduino components like LEDs and motors yet here I am, still alive. What am I missing? \$\endgroup\$ – StellarEquilibrium Nov 1 '18 at 12:52
  • \$\begingroup\$ Remember the charts you are referencing are ac not DC. DC is 3-5 times safer than ac at the same current level. Your body resistance can vary from 500 ohms (broken skin - cold sores, cut) to 50000 ohms. Do Ohm's Law on 5V at 500 ohms and it's only 10mA. Well below safety issues. I've worked 40+ years on electronics (<15V), with no major concern for safety. I've also worked on AC motors (>120V), where safety is a concern. Lock out, tag out, probe contacts before touching, etc. But fundamentally the same practices I use for DC are strictly followed. \$\endgroup\$ – StainlessSteelRat Nov 1 '18 at 15:48

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