I’ve just bought ARDUINO UNO R3 and I heard a lot that it’s was safe because of low voltage, I having a hard time trying to figure out why !
As far as safety to humans, anything below 50V is generally considered safe.
Most regulations require anything above 50V to be insulated/isolated so you can’t touch it. (That’s for “consumer products”… For example, you can buy a high voltage power supply with exposed terminals but in the “final design” you’re supposed to enclose the thing and insulate the wires/connections.)
That’s voltage… Current (Amps or milliamps) depends on voltage and resistance ([u]Ohm’s Law[/u]).
Resistance means the “resistance to the flow of current”.
Your body has very-high resistance so for example, you can touch a 12V car battery that’s capable of hundreds of amps and it’s safe. (An inductive load or spark plug coil in a car can generate enough voltage to shock you.) With nothing connected to the battery, no current flows. If you connect a regular little LED to a car battery with the appropriate current-limiting resistor, you’ll get 10 or 20mA. Turn on your headlights and a lot more current flows (though the lights).
Same thing with the Arduino’s 3.3V connection. With nothing connected no current flows out. If you connect an LED (with the proper resistor) you’ll get 10 or 20mA. If you connect 10 LEDs, you’ll get excess current… The voltage will drop and you might damage the Arduino.
If I take body_R = 1kohm it makes
If your body measures 1K your meter is broken!
or above 10mA it can be dangerous and 50mA is deadly. So, where is the mistake ?
The spec actually says 50mA maximum so above 50mA it could be “deadly” to the Arduino, but NOT to you! (because that current isn’t flowing through your body.)
The most “dangerous” thing about touching an Arduino (or any PC board) is a[u]static discharge[/u] from your body. …You know when you touch something like and get a spark and sometimes a little shock? If you have a charge on your body and you touch a circuit board you can kill it! …Sometimes the discharge is too small to feel, but then your chip dies “for no reason”.