Tesla coil safety questions, risk analysis quantified

[Michelle_]

Hi, I'm looking for specific information about how dangerous different types of tesla coils are. Apparently you can touch some of the arcs no problem, but other arcs will kill you.

Imagine there is a matrix of danger where a 1 is minimal or no risk to a 10 is immediate death.

Lets then say the other side of the matrix ranges from zapping to burning with A (only a shock) B (shock and burn) C (only burn)

How do things like Voltage, Frequency, and current play into these levels of threat (specific ranges and values would be helpful)

What is the difference between "lightning arcs" and "plasma flames"?

Furthermore are there generalizations of TYPES of tesla coils that lend themselves to particular ranges of danger, e.g. a spark gap, SSTC, etc...?

I also understand that there's a relationship between output voltage and arc lengths, but not sure about current.


THANK YOU if you take the time to spell this out for me! It might also help someone else that searches. Please don't tell me "they can all be dangerous" I'm looking for more specific information.

[MRMILSTAR]

The answers to that question are wide-ranging and would encompass an entire academic study which has never been done. In general, I would advise the following.

I wouldn't touch any Tesla coil streamer if it has an output power of more than a few watts. Those small Tesla coils which you see on E-Bay and plasma globes are OK. Even for larger coils, you may not feel much but the current is passing through your body. You don't have much sensation of pain because nerve cells do not respond very well to high frequency current. The current will also follow the paths of least resistance such as blood vessels and nerve fibers. Don't believe the skin effect myth that you may read about. The skin effect is only significant for excellent conductors such as copper. For a poor conductor such as the human body, the skin depth essentially extends through your entire body. The current flowing through your body heats internal organs, with the heating depending on the power level.

In my opinion, its just not worth risking your health just to demonstrate that streamers can strike your hand with no apparent effect. You are essentially experimenting with yourself. Would you feel comfortable with using your body as a wire? In effect, that is what you would be doing. Nerve damage can take years to manifest itself.

[Michelle_]

The answers to that question are wide-ranging and would encompass an entire academic study which has never been done. In general, I would advise the following.

I wouldn't touch any Tesla coil streamer if it has an output power of more than a few watts. Those small Tesla coils which you see on E-Bay and plasma globes are OK. Even for larger coils, you may not feel much but the current is passing through your body. You don't have much sensation of pain because nerve cells do not respond very well to high frequency current. The current will also follow the paths of least resistance such as blood vessels and nerve fibers. Don't believe the skin effect myth that you may read about. The skin effect is only significant for excellent conductors such as copper. For a poor conductor such as the human body, the skin depth essentially extends through your entire body. The current flowing through your body heats internal organs, with the heating depending on the power level.

In my opinion, its just not worth risking your health just to demonstrate that streamers can strike your hand with no apparent effect. You are essentially experimenting with yourself. Would you feel comfortable with using your body as a wire? In effect, that is what you would be doing. Nerve damage can take years to manifest itself.

I'm not trying to touch them or show off, "small tesla coil probably ok, big one bad" yes I already know this. I'm trying to make sense of comments from people such as electroboom on youtube saying it will burn you at X frequency or it only hurts at Y frequency, etc... Also I don't know how to estimate the output wattage of a tesla coil but apparently everyone else already knows all of this stuff.

I hate asking these kinds of questions. I'm not an idiot or a showoff, I know people know generalized answers to everything I asked. I'm not here to be patronized by experts just because I'm a beginner trying to understand something.

[Mads Barnkob]

I usually refer to this Tesla Coil safety guide: https://www.pupman.com/safety.htm

[alan sailer]

Michelle,

Your questions are all valid questions but as MRMISTAR says, no-one really has all the answers.

For one thing, try and imagine how a study could be done to determine the risk of various voltages and currents and frequencies.
On people? No ethicist would consider such a study. I'll bet that all the information we have is based on unfortunate accidents and
measurements of what happened could only be done after the fact.

Tesla coils, in addition, are a very, very fringe section of the worlds electrical hazards. No government agency is going to get
into tesla coil safety. That leaves coilers themselves to answer these questions. And coilers run the range from highly competent
electrical engineers to total nutcases. Align your auras with my biogenic tesla coil? Free zero point energy? :-)

Another factor is that people vary in their hearts sensitivity to currents. In addition variations in internal anatomy might mean
that in one person a deadly current passes through their heart and in another person that same current passes a few inches to
one side leaving them hurt but alive.

I've watched a few do the volts kill or does the current kill YouTube stuff. Besides being a basically ridiculous click-baity statement whenever
I watch such a video at some point I end up doubting some of what is being said. They are entertaining but I would not take any one
of them as all truth. Incidentally, this does not mean that I know the truth :-)

On a side topic, a few years ago I found about a terrifying effect known as arc flash. I was looking into voltmeters and found out that
they were rated for what kind of circuit they were safe to work with. It all has to do with the internal fuses of the voltmeter and what
levels of current the fuse works with. Use the wrong voltmeter and you can die from arc flash.

https://www.fluke.com/en-us/learn/blog/safety/arc-flash-vs-arc-blast

Cheers.

P.S. I enjoy ElectroBoom and his videos are really interesting. But his running joke of "electrocuting" himself at some point in each video makes
me cringe. The idea of shocking yourself for someones else's entertainment is just dumb. I can only hope no-one out there is attempting to imitate him...

[Michelle_]

Thanks for the links.

I actually know all about arc flashes and safety of industrial electronics. I’ve designed and built panels as well as trained technicians about safety. I’m actually an engineering manager now and I always go through arc flash hazard stuff with people, and regularly stop people that are building machines from trying to turn on the disconnect with the panel door open.

Like I said I’m not a random idiot trying to shock myself with a Tesla coil.

What I want to know is why is a “small” Tesla coil safe to touch and a big one not. I realize that the issue is complicated but I was hoping for some generalizations because apparently some people have a really great sense of what is too dangerous to mess with and what isn’t. Say what you will about electroboom but he is an electrical engineer and understands very well what he is doing. He stages every single one of his videos for entertainment and calculates every risk, with the exception of the time his Jacob’s ladder fell on him.

Other YouTubers ready start touching their Tesla coils. I know there are some parameters or thresholds that will spook some people and I’m trying to figure out what they are instead of getting typical hand wavey answers about not touching arcs which believe me I already know and again im not trying to do that.


Anyways i guess this was a bad question to ask and ill just have to do research on my own to have some perspective about how powerful of a Tesla coil is remotely safe to operate nearby, indoors, etc…

[alan sailer]

At the risk of sounding dumb, a small tesla coil say one of those Chinese tabletop units runs at about 50 watts.
Say the output voltage is 50kV. Assuming 100% efficiency then the output current is 1mA. The accepted threshold
for heart stopping is 50mA.

Take another coil Brodin. Puts out 15 foot arcs. Runs 40kW. I have no idea what it's output voltage is but lets say 100kV.
Now the output current is 400mA. Nice death number.

There is also another arc flash type situation that can occur in tesla coils. Say you are running a medium sized tesla coil with
300 volts on the primary. Say it's running 2kW input power and 70kV output voltage. So 28mA on the secondary. Not quite deadly.
But you are taking that arc and doing fine. Then the secondary makes a strike to the primary winding, the one with 300 volts
and lots of amps. then the coil changes its mind and sends an arc back to you. But now that ionized arc channels that was
connected to 300 volts is connected to you. And instead of getting the secondary current you are now getting the primary
current of nearly 10 amps average.

All these numbers are wild guesses and mix up peak and average like crazy. But the bottom line is a bigger coil uses more wattage.
And that wattage makes it more dangerous.

I will also say that labeling your question a bad question is just not right. It's a very difficult (I'd guess impossible) question to answer
but that does not make it bad.

Cheers.

PS You will note I have nothing bad to say about ElectroBooms competence. He knows more than I know about electricity. I just dislike
his shock stuff.  I simply don't like making electrocution into a joke.

PPS When I was starting out in electronics a long, long time ago one of the sayings was "Tarry not among those who engage in intentional
electrical shocks, for they are not long to this world."

[Michelle_]

At the risk of sounding dumb, a small tesla coil say one of those Chinese tabletop units runs at about 50 watts.
Say the output voltage is 50kV. Assuming 100% efficiency then the output current is 1mA. The accepted threshold
for heart stopping is 50mA.

Take another coil Brodin. Puts out 15 foot arcs. Runs 40kW. I have no idea what it's output voltage is but lets say 100kV.
Now the output current is 400mA. Nice death number.

There is also another arc flash type situation that can occur in tesla coils. Say you are running a medium sized tesla coil with
300 volts on the primary. Say it's running 2kW input power and 70kV output voltage. So 28mA on the secondary. Not quite deadly.
But you are taking that arc and doing fine. Then the secondary makes a strike to the primary winding, the one with 300 volts
and lots of amps. then the coil changes its mind and sends an arc back to you. But now that ionized arc channels that was
connected to 300 volts is connected to you. And instead of getting the secondary current you are now getting the primary
current of nearly 10 amps average.

All these numbers are wild guesses and mix up peak and average like crazy. But the bottom line is a bigger coil uses more wattage.
And that wattage makes it more dangerous.

I will also say that labeling your question a bad question is just not right. It's a very difficult (I'd guess impossible) question to answer
but that does not make it bad.

Cheers.

PS You will note I have nothing bad to say about ElectroBooms competence. He knows more than I know about electricity. I just dislike
his shock stuff.  I simply don't like making electrocution into a joke.

PPS When I was starting out in electronics a long, long time ago one of the sayings was "Tarry not among those who engage in intentional
electrical shocks, for they are not long to this world."

No risk of sounding dumb. I realize there are a lot of factors and you are generalizing but your reply is very helpful. I agree that electrocution is not a joke and that's why I made this thread, because before I mess with anything more powerful than my tiny slayer exciter I wanted to have a more intuitive sense of what's going on. All of this is VERY different than working on a three phase panel. (un)funny story, one time I got a call from a production lab and a technician said one of our 480v panels had an arc flash. I told them to shut down all the breakers and I went over there immediately expecting to find a fire and or burn injuries. What actually happened was there were just sparks coming from a 24v power supply, and nobody understood why I was so pissed off about that lol (but also relieved).

So anyway how I understand it, is to make relatively safe tesla coils that can be used indoors or near people, the important thing is quantifying the input wattage, estimating the output voltage; and then the output current.

That's a good point about the primary voltage jumping to the secondary. Also I've gotten a chance to look more closely at the link above and it kinda addresses most of the stuff I was wondering about.

I'm not trying to put on a lightning show and I'm not quite ready to die yet, so I'm going to stick to pretty reasonable DC voltages for what I'm building. I just wasn't sure where to draw the line or quantify how "powerful"  a tesla coil is besides how big it is (can't always judge things by their size) or "seems like".

Thank you!

M

[alan sailer]

I have noticed that you are interested in the plasma toroid also. Low enough power not much danger. However, the node at the connection between the output inductor and the 100pF (usually) capacitor has some high voltage >1kV. It would painful if touched but should not be deadly.

I had a scope probe body touch that node when looking at the circuit waveforms recently. The result was small smoke and flame, AKA "An ElectroBoom".

I was not amused...

Cheers.

[Michelle_]

I have noticed that you are interested in the plasma toroid also. Low enough power not much danger. However, the node at the connection between the output inductor and the 100pF (usually) capacitor has some high voltage >1kV. It would painful if touched but should not be deadly.

I had a scope probe body touch that node when looking at the circuit waveforms recently. The result was small smoke and flame, AKA "An ElectroBoom".

I was not amused...

Cheers.

Thanks for the heads up. I'll definitely be probing that circuit and I really truly don't want any explosions or to damage my scope.

[sky-guided]

I have noticed that you are interested in the plasma toroid also. Low enough power not much danger. However, the node at the connection between the output inductor and the 100pF (usually) capacitor has some high voltage >1kV. It would painful if touched but should not be deadly.

I had a scope probe body touch that node when looking at the circuit waveforms recently. The result was small smoke and flame, AKA "An ElectroBoom".

I was not amused...

Cheers.

Funny story that's exactly how I learned the hard way what a (thankfully very minor) HV-RF burn feels like. Super weird now it takes a couple days for the injury to really develop.

Smoked a scope probe too.