Any electric shock risk ?

Hi everyone. I have an Uno and i do simple led button projects. Im curious that is there any risk of shocked by electric while Arduino is connected to the PC and touching, moving pins,cables on the breadboard. Its hard to plug in/out the usb everytime. I touched the resistors couple of times, i didnt notice something but im not sure if it is %100 safe. Thanks.

Absolutely no problem from a USB or anything below 24 volts. You have to get above around 40 volts before you have potential problems (excuse the pun)

Some useful information at http://www.mpoweruk.com/shock.htm

jackrae:
Absolutely no problem from a USB or anything below 24 volts. You have to get above around 40 volts before you have potential problems (excuse the pun)

Some useful information at http://www.mpoweruk.com/shock.htm

Thanks for your answer. The table in the website says that 20mA will make a painful shock but i already used 5V and 220 ohm resistor with a led and didnt notice anything. Whats the reason for this, am i calculating wrong ?

Hi,
The 20mA has to flow though you body, and using Ohms Law, 5V across many 100K ohms will not produce 20mA.

Tom... :slight_smile:

Yes. The computer usb only provide 5 volt and 50 to 100 mA current.
But make sure your AC power line is properly grounded ?. MCB is installed at your working place ?.

The IEC requirement for installing shock protection shielding is 30 volts.

I learned this years ago when I was designing a system needing loads of control panels distributed around a big televison studio and wanted to use 'open frame' contruction to reduce costs.

Mains power supplies would require expensive metal casings, and distruting 5v dc would require thick wires, so I installed a big 24v toroidal transformer in the central controller, and distributed that ( individually fused) along with the control signals to each panel, which had a 24-7v step down transformer and a linear psu to get 5v.

In the late 70's switchers were not freely available and wall warts didn't exist..

Saved loads of money.

Allan.

I dont have knowledge about grounding the AC line or installing MCB. Some people says its safe other says its unsafe. How do you work on your Arduino ?

allanhurst:
The IEC requirement for installing shock protection shielding is 30 volts.

I learned this years ago when I was designing a system needing loads of control panels distributed around a big televison studio and wanted to use 'open frame' contruction to reduce costs.

Mains power supplies would require expensive metal casings, and distruting 5v dc would require thick wires, so I installed a big 24v toroidal transformer in the central controller, and distributed that ( individually fused) along with the control signals to each panel, which had a 24-7v step down transformer and a linear psu to get 5v.

In the late 70's switchers were not freely available and wall warts didn't exist..

Saved loads of money.

Allan.

So, you mean it's safe to touch conductives up to 30 volts ? Thanks.

Think about it, have you seen a child's electric train set or a scalextric racing set. Raw 12V all over the place and no sign of anyone ever getting a shock.

I dont have knowledge about grounding the AC line

You don't have to, a wall wart is isolated from the mains, there is no need to ground anything.

Grumpy_Mike:
Think about it, have you seen a child's electric train set or a scalextric racing set. Raw 12V all over the place and no sign of anyone ever getting a shock.
You don't have to, a wall wart is isolated from the mains, there is no need to ground anything.

Is it about the current or volt and also i use a laptop to power(sometimes on battery) should i ground something ?

Is it about the current or volt

Both.
But a 5V 1A power supply presents exactly the same risk as a 5V 40A power supply. Many beginners think a 40A power supply will drive 40A through anything. It only drives the current that can flow from 5V divided by the resistance between the positive and negative of the supply. This is called ohms law, although it should be called Ohm's law.

You need the voltage to drive the current through the body.
With a low voltage ( in Europe less than 50V is considers low ) you can't drive any significant current through your body unless you have electrodes made of thumb tacks and push them in your wrists.

Grumpy_Mike:
Both.
But a 5V 1A power supply presents exactly the same risk as a 5V 40A power supply. . .

To be more clear, a 5V 1A power supply presents exactly the same shock risk as a 5V 40A power supply since the current is limited by your body's electrical resistance to something considerably less than 1A.

If a low resistance short is accidentally presented across these two power supplies then the 40A power supply has considerably more potential to melt wires and such. For this reason it is generally recommended to wear eye protection when working on circuits with high current potential.

They say amps kill you not volts. Don’t think of it that way. In order to get any amperage to flow through you, you need sufficient voltage to overcome the electrical resistance of your body.

Some bodies are 100 ohms under the right conditions, when the path is right across your chest and you’re soaked in salty perspiration. Other bodies are 1000 ohms or more. This means the voltage needed to pass a given amount of current through your vital organs varies from body to body and also varies with the electrical pathway (from one leg to another? Leg to opposite hand? Armpit to armpit?). To complicate things further, unbroken skin tends to dissipate most electrical current flowing through you so even electrocution that you can feel won’t necessarily kill you because very little of it goes inside your body instead of passing over the surface.

Generally, <50V you’re probably not at risk in most cases. Above that, start taking precautions. An Arduino may be capable of passing 40mA within itself (because it’s made of conductive metals) but that 40mA will never pass into you no matter how hard you try because it’s not 40mA anymore when it touches your high resistance body. The voltage that made the 40mA was only 5V and that could never electrocute you.

Just curiosity - does anybody know what voltage/current and pulselength a pacemaker generates?

Not my field....

Allan

allanhurst:
Just curiosity - does anybody know what voltage/current and pulselength a pacemaker generates?

Not my field....

Allan

I don't know, but I had a tens unit that could put your arm into seizures. It had a warning about putting it across your chest. I'm not sure if it could reach in far enough to damage your heart, but I wasn't going to be the dummy to prove it one way or the other

Don't know about the pacemaker but defib kits can deliver up to 360 Joules in the form of a monophasic or biphasic pulse ranging from 10 to 40 amps (varies based on design). The numbers change significantly if you're delivering the shock from inside the body.

Hi,

https://galileo.seas.harvard.edu/images/material/3794/1321/CardiacPacemakerdesign.pdf

Looks like its mV due to the intimate contact with the heart nerves.

Tom... :slight_smile:

Sigh ... You guys! :wink:

Kalender:
Hi everyone. I have an Uno and i do simple led button projects. Im curious that is there any risk of shocked by electric while Arduino is connected to the PC and touching, moving pins,cables on the breadboard. Its hard to plug in/out the usb everytime. I touched the resistors couple of times, i didnt notice something but im not sure if it is %100 safe. Thanks.

The bottom line is that no, with your Arduino connected to a computer, there is absolutely no danger from electrical shock.

There IS a danger, but it is to the components on your board, say if you accidentally connect a pin that is high to a ground, you will exceed the current the pin can carry, and burn it out. But you? You are safe - plug and unplug with confidence!

ChrisTenone:
Sigh ... You guys! :wink:

The bottom line is that no, with your Arduino connected to a computer, there is absolutely no danger from electrical shock.

There IS a danger, but it is to the components on your board, say if you accidentally connect a pin that is high to a ground, you will exceed the current the pin can carry, and burn it out. But you? You are safe - plug and unplug with confidence!

Hi. Do you mean that the board of the Arduino will burn or the computer ?

Old apprentice saying "It's the volts that jolts but the mills that kills"

We used to have a TV repair man in our workshop who regularly tested the output of a monitor's line-output transformer (in the days of valves / tubes) by drawing an HT spark ( several thousand volts) with his finger. It did indeed 'tingle' but the current available was too low to cause damage.

I shouldn't admit to this but I regularly 'test' the classic PP3 sized 9volt battery using my tongue :confused: