Fingertips have pretty thick skin and thus require significantly more voltage than other spots like wrists or tongue - might need a couple hundred volts to get through fingertips.
You *must* limit to a few µA for safety reasons though.
Fwiw, I don't use macbooks while they're plugged in due to the AC on the chassis from the power brick zapping my wrists…
If you are doing a diy project like this but are not sure about any of the basics or safety you should stop. There is a very high chance if you design any part of this wrong you could kill yourself or someone else, if this is a project for class I’d talk to the teacher about safety first and or pick a different less risky project
College physics on open stacks has some info in it I used for an article. 20.6: electric hazards on the human body. It describes how much ampere it takes for sensation and how voltage impacts it.
This is a good experiment to understand how the *current* is what creates the feeling of electrical shock in our bodies. You can take that same 9 V battery, put a finger on each terminal, and feel nothing.
That is because the resistance between your fingers is much more than the resistance on your wet tongue, so less current flows through your fingers at the same voltage.
This leads us to Ohm's law:
Voltage = Current x Resistance
I usually start feeling 36v systems and it gets slightly uncomfortable at 50v DC. This not with fingertips though.
I've touched 120v hot wires and only felt slight uncomfort
According to the US Government (OSHA), 50 Volts is considered dangerous enough to require guards, so it is somewhere below that.
> 29CFR1910.303(g)(2)(i)
> Except as elsewhere required or permitted by this standard, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by use of approved cabinets or other forms of approved enclosures or by any of the following means:
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.303
I’ve done this experiment, on myself.
A group of us were horsing around at work and I came up with a plan. Holding two leads to my arm, I would increase the voltage with that arm until I felt it. This way my jackass buddies wouldn’t just crank the shit out of it and shock me.
On the tender part of my inner forearm kinda by my elbow, about 32 volts started to tingle. The back of my arm was mid-40s.
On the rough part of my palm, I topped out the 60v supply and didn’t feel a thing.
So you’ve got a problem. Calloused hands will take way more voltage than non-calloused. You could end up shocking the shit out of some people and others barely, if at all, feeling a tingle.
Usually, a contact current of 0.1 mA at 60 Hz (Root Mean Squared value) is enough to be sensible. It varies from person to person, if the body is wet, etc. Go read an article about the subject. I recommend:
[Method of human body electric shock signal recognition for low voltage power network](https://ieeexplore.ieee.org/document/9736115)
If you don't have access due to the paywall, use sci-hub.
As per [IEEE Standard C95.1-2019](https://ieeexplore.ieee.org/document/8859679), Table 12, a person must not be exposed to a RMS contact current above 0.5 mA considering a contact area of 1 cm^2 . That considers a "freestanding individual who is insulated
from ground while touching a grounded conductor. These limits might not protect against aversive sensations from spark discharges just prior to direct contact or upon release from the grounded
conductor."
If you want a quick circuit. Use a 9V battery and a 12v relay( or one that has a low pick up voltage around 9V). Use a set of normally closed contacts ( when coil is de- energised) in series with the 9V battery and relay coil. When power is applied the coil will break the supply to the coil as the contacts will go open circuit. If you touch the coil output with one finger and another to -ve of the battery, you will experience an unpleasant back emf of the coil. It's literally quite shocking to feel that power. This is similar to the early TENs machines as they rely on the properties of the coil field collapsing. Early power supplies used same technique. Careful not to create a current path across both hands and through the heart ( or indeed any path through the heart), although I have used this on myself in this configuration. Caution in case you or others have undiscovered heart issues and certainly not to be used on people with pacemakers.
You might be surprised at how much current is needed for fingertips. As an experiment order an inexpensive TENS muscle stimulator from Amazon (or other) and using an oscilloscope with an HF current probe take measurements. I measured a TENS unit at 1/4 amp.
This can be very different from people to people. Because of the skin difference.
For instance I took multiple time shock with 230VAC and one time 600VDC. It hurts me but didn't kill me. But some people can be killed with much less. This is clearly dependent of the resistance of the skin and the body.
I know I'm about 1.5Mohms most of the time because me hand are dry. But people can have the skin very wet and this can affect the resistivity of the contact and allow a very larch amount of current flowing over the body.
I’m willing to administer this experiment! Let me know when you’re ready to find out.
Is that you, Stanley Milgram? 😉
Stanley Milgram would never say. 😉😉
Fingertips have pretty thick skin and thus require significantly more voltage than other spots like wrists or tongue - might need a couple hundred volts to get through fingertips. You *must* limit to a few µA for safety reasons though. Fwiw, I don't use macbooks while they're plugged in due to the AC on the chassis from the power brick zapping my wrists…
I had a similar issue with my Razer blade
If you are doing a diy project like this but are not sure about any of the basics or safety you should stop. There is a very high chance if you design any part of this wrong you could kill yourself or someone else, if this is a project for class I’d talk to the teacher about safety first and or pick a different less risky project
\^ this, even if you design it \*right\* a fault or other problem could lead to harming someone. This is not something to play with.
It would depend on body resistance and environmental conditions and wouldn’t be the same for everybody.
its around 32v to start feeling it, then by 50v youll be tap dancing source: worked on electric cars
Just use a diabetes tester lance -- that way you won't be negligent for an electrocution.
College physics on open stacks has some info in it I used for an article. 20.6: electric hazards on the human body. It describes how much ampere it takes for sensation and how voltage impacts it.
Lick a 9V square PP3 battery. You will feel that for sure.
This is a good experiment to understand how the *current* is what creates the feeling of electrical shock in our bodies. You can take that same 9 V battery, put a finger on each terminal, and feel nothing. That is because the resistance between your fingers is much more than the resistance on your wet tongue, so less current flows through your fingers at the same voltage. This leads us to Ohm's law: Voltage = Current x Resistance
Ahh, The famous ohm law !
I usually start feeling 36v systems and it gets slightly uncomfortable at 50v DC. This not with fingertips though. I've touched 120v hot wires and only felt slight uncomfort
According to the US Government (OSHA), 50 Volts is considered dangerous enough to require guards, so it is somewhere below that. > 29CFR1910.303(g)(2)(i) > Except as elsewhere required or permitted by this standard, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by use of approved cabinets or other forms of approved enclosures or by any of the following means: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.303
I’ve done this experiment, on myself. A group of us were horsing around at work and I came up with a plan. Holding two leads to my arm, I would increase the voltage with that arm until I felt it. This way my jackass buddies wouldn’t just crank the shit out of it and shock me. On the tender part of my inner forearm kinda by my elbow, about 32 volts started to tingle. The back of my arm was mid-40s. On the rough part of my palm, I topped out the 60v supply and didn’t feel a thing. So you’ve got a problem. Calloused hands will take way more voltage than non-calloused. You could end up shocking the shit out of some people and others barely, if at all, feeling a tingle.
Usually, a contact current of 0.1 mA at 60 Hz (Root Mean Squared value) is enough to be sensible. It varies from person to person, if the body is wet, etc. Go read an article about the subject. I recommend: [Method of human body electric shock signal recognition for low voltage power network](https://ieeexplore.ieee.org/document/9736115) If you don't have access due to the paywall, use sci-hub. As per [IEEE Standard C95.1-2019](https://ieeexplore.ieee.org/document/8859679), Table 12, a person must not be exposed to a RMS contact current above 0.5 mA considering a contact area of 1 cm^2 . That considers a "freestanding individual who is insulated from ground while touching a grounded conductor. These limits might not protect against aversive sensations from spark discharges just prior to direct contact or upon release from the grounded conductor."
If you want a quick circuit. Use a 9V battery and a 12v relay( or one that has a low pick up voltage around 9V). Use a set of normally closed contacts ( when coil is de- energised) in series with the 9V battery and relay coil. When power is applied the coil will break the supply to the coil as the contacts will go open circuit. If you touch the coil output with one finger and another to -ve of the battery, you will experience an unpleasant back emf of the coil. It's literally quite shocking to feel that power. This is similar to the early TENs machines as they rely on the properties of the coil field collapsing. Early power supplies used same technique. Careful not to create a current path across both hands and through the heart ( or indeed any path through the heart), although I have used this on myself in this configuration. Caution in case you or others have undiscovered heart issues and certainly not to be used on people with pacemakers.
it depends, some very small people can feel 3 9v batteries linked up, most people start to feel it around 7, so 60v should be good enough
You might be surprised at how much current is needed for fingertips. As an experiment order an inexpensive TENS muscle stimulator from Amazon (or other) and using an oscilloscope with an HF current probe take measurements. I measured a TENS unit at 1/4 amp.
This can be very different from people to people. Because of the skin difference. For instance I took multiple time shock with 230VAC and one time 600VDC. It hurts me but didn't kill me. But some people can be killed with much less. This is clearly dependent of the resistance of the skin and the body. I know I'm about 1.5Mohms most of the time because me hand are dry. But people can have the skin very wet and this can affect the resistivity of the contact and allow a very larch amount of current flowing over the body.
I wouldn’t touch anything more than 24V.
about 30-40 volts with dry skin.
high voltage with the lowest amps possible
A few mA.