static electric generator safety questions - Page 1
Forum section: electronics / projects

author: djf123
author_rank: Newbie
timestamp: January 18, 2021, 01:34:36 am
content: So I saw this cool youtube video about a static electric generator somebody made, and so I decided to try to make one myself.I was concerned though about the safety as it seemed pretty ballsy of the guy to just make it and touch it without first knowing all of the circuit component's values. My question though is, How would you go about measuring the discharge current to make sure it was safe to touch? What instrument would you use to to do so and what settings would you use on the instrument to do so? And what maximum current would be unsafe?Also, I was looking at the video and the little cheap electronic ionizer device has a high voltage wire way far away from the ground. So I didn't understand how the device could possibly cause any air ionization to begin with because I thought you needed something like 3 million volts per meter. For some reason the device just had these black hairlike brushes on the high voltage wire that is like 3 inches from the ground. Does this device even work to ionize the air or is it a scam?

author: bob91343
author_rank: Super Contributor
timestamp: January 18, 2021, 01:41:49 am
content: While your questions seem reasonable, unfortunately they relate to a rather complex situation. High voltage, ionization, personal safety are all intermingled and there is no clear answer.The worst thing with high voltage is excessive current through the heart, sustained long enough to cause its muscles to spasm. How that can happen isn't an easy determination.Look at lightning for an example of a big spark across a great distance. When you have a very strong charge, molecules in the vicinity turn in a particular direction that can spread the ionization region over a large volume.Rather than elaborate (on a subject with which I am less than familiar) I refer you to textbooks and googles on this phenomenon, although here is a classic case of needing substantiation of any statements you read.The above paragraphs are a fancy way of saying that I don't know.

author: djf123
author_rank: Newbie
timestamp: January 18, 2021, 01:53:48 am
content: I was just assuming that with a device like the guy made that when you were connected to it and touched ground creating a spark there would be a sudden spike in the current and then an exponential decay to zero current. And that if the maximum current of the spike was too high it would be unsafe.What I was interested in was knowing what device could be used to measure that suddenly changing current and thus the maximum current. Would it be some sort of special type of multimeter or a type of oscilloscope or some other electronic instrument I am unfamiliar with? Would a high voltage probe be needed?There must be a standard way to verify the safety of circuits like these.

author: helius
author_rank: Super Contributor
timestamp: January 18, 2021, 03:20:49 am
content: The safety of any line-powered device is a function of its insulation resistance. So-called "Hi-pot" testers are used to verify the insulation holds up to a test voltage around 4–5 kV. Higher voltages are used to test transmission wiring.For the specific situation of a Van de Graaf generator, the charge available is rather low, since it must all be on the outside surface of the dome. Demonstrations of static electricity with these devices are (or were) common in grade schools. For the accumulation of charge to work, the dome must be very well insulated from the line side: so you could say that they are intrinsically safe.A high voltage probe will let you measure the voltage between the dome and ground—however, commonly available probes are limited to around 50kV and won't withstand the higher voltage on a fully charged Van de Graaf generator. If its rated voltage is exceeded, the probe can break down (spark) internally and become damaged, which can also damage the attached meter. For measuring these types of equipment the best instrument is a static locator, which can read the electric field from a distance (based on air ionization).

author: bob91343
author_rank: Super Contributor
timestamp: January 18, 2021, 06:36:17 am
content: An exponential decay to zero current is an oxymoron. Exponential means it never reaches zero but gets closer and closer, more and more slowly.There are electrostatic voltmeters capable of measuring high voltage. In this case it's very true that measuring something changes it. An electrostatic voltmeter has infinite resistance but since it's a motor, will draw current while the pointer is moving. So measuring a static charge will draw off some of the charge.This is a popular subject because it can be very showy with sparks and crackles, mostly with limited control.The real answer to the safety question lies in the amount of charge involved. If capacitance is low, as it usually is in these demonstration equipments, there isn't enough energy to cause bodily harm, even at very high voltages. The energy in Joules is 0.5*C*V^2 if I remember correctly. How many Joules can cause harm? I don't know. It certainly depends on the time frame; you can withstand many Joules if the time involved is long.

author: jonpaul
author_rank: Super Contributor
timestamp: January 18, 2021, 09:42:27 am
content: Bonjour, This is an inverter and transformer driving a 4 stage Cockcroft-Walton multiplier,https://en.wikipedia.org/wiki/Cockcroft–Walton_generatorThe 4 SMD HV caps are likely ~ 1 nF.A spark might not do damage, BUT the reaction to the shock can cause a fall or other reaction.HEART PACEMAKER USERS BEWARE OF DEATH! STAY AWAY!You can be sure that safety is not a concern of the Chinese manufacturers, just to sell their junk to us and make money.Bon Chance,Jon