What guage wire?

[Kissmabass]

Hi everyone,

I'm making my first spud cannon and I have a couple of questions. First off, I am using the VIPERTEK VTS-979 as my ignition source. I was wondering what gauge wire I should use? It claims it is 19,000,000 volts which I am not sure is true, and I have no idea what gauge wire to use.

Also, any recommendations on how to connect the wire to the diode? I was thinking electric crimps.

Thanks everyone for your help!

[jrrdw]

Use the same guage as the out put. I myself prefer to solder but crimps work well.

[mark.f]

Gauge has nothing to do with the insulation on the wire. That being said, most wire will work with moderate separation, and wire like the kind used on multimeter test leads is usually plenty sufficient.

[Technician1002]

19 thousand or 19 million? High tension lines strung from towers are rarely over 1 million becasue the air will break down and it leaks away. Most high voltage power lines (the big ones) are typically 1/2 megavolt maximum. Linked is an example of what less than 1 megavolt will do.

Your module will not produce this high current, so it won't be as pretty.
The line in the video is a 500KV line.



A claim of 19 Million volts in air in a gap under 3 feet is fantisy, not reality.

[DYI]

1. Apart from concern about the field gradient inducing breakdown in the surrounding air and insulation (which would be a major concern at 19MV), the diameter of the wire has nothing to do with the voltage. I get the feeling that you may be conflating the voltage difference between the wire and the air with the resistive heating caused by running a high current through the wire, which is the limiting factor on wire diameter in most cases.

2. The device you mention is not physically large enough to generate a 19MV potential difference within its body - there do not exist materials with sufficient dielectric strength, regardless of any other limiting factors. 50kV perhaps, which would be more than adequate for any self defense purposes (all it needs to do is break down an air gap of at most the distance between the prongs, maybe 1.5 inches).

With those points of confusion out of the way: choose a high voltage wire class sufficient to hold off the maximum voltage that will be developed between the two stungun leads, which will be on the order of 50kV (if your total spark gap is 2" wide and operating at atmospheric pressure in something resembling air). This ensures that your design won't experience ignition failure due to unwanted arcing elsewhere in the system. It tends to be easier to use shorter gaps and thus lower voltage - I use a 30kV source for all my HV ignition needs, which reduces the cost of the requisite high voltage wire.

[Kissmabass]

Yeah I thought that the 19 million volts was ridiculous. I read that Amps determines what gauge wire to use for wiring, not volts. I saw a chart that said anything under 9 amps and 4 ft long, 12 gauge wire is fine. I also read all stun guns just have 4-5 milliamps because 1 amp can easily kill.

DYI: do you have a brand that makes high voltage wire?

[Technician1002]

Yeah I thought that the 19 million volts was ridiculous. I read that Amps determines what gauge wire to use for wiring, not volts. I saw a chart that said anything under 9 amps and 4 ft long, 12 gauge wire is fine. I also read all stun guns just have 4-5 milliamps because 1 amp can easily kill.

DYI: do you have a brand that makes high voltage wire?

12 gauge is too big to be pratical. Larger diameter wire has higher capacitance per foot and will impact your voltage over longer distance. For the voltage, you will want proper insulation. Household wire in the US is typpically listed for up to 600V. For your application, you will want either ignition wire (automotive spark plugs) or Neon sign wire. They can be obtained from an auto parts store or sign shop.

Note that most ignition wire does not have a metal wire in it, but a carbon or other high resistance core to suppress ringing that causes lots of static on the radio. Solid wire can sometimes be found as a racing wire for higher current applications. If you use normal ignition wire, you will need to use and modify the spark plug ends for it as the core can not be treated as a normal metal wire under any stretch of the immagination.

[jimmy101]

For a 50KV spark system the gauge of the wires is really pretty irrelevant. 10G would work. 30G would work (and be more flexible and cheaper). Insulation is important but at 50KV a plastic sheath really won't do much unless it is absurdly thick. As a practical matter "insulation" in high voltage systems is often just a large air gap between the wires.

A "50KV" ignition system really doesn't operate at that voltage. The maximum voltage the system will generate is determined by the spark gap. If the spark gap brakes down (sparks) to 10KV then the ignition system's voltage never exceeds 10KV. A HV system can only really generate its maximum voltage in cases where it doesn't actually spark.

[Kissmabass]

Well I finally got everything wired up and it was working perfectly. Until this morning when the stun gun decided to stop working. It still is turns on and everything, it is just not arcing across the gap. It makes a high pitched noise when I press the engage button, but no arc. I read that could be a internal arc that is occurring, but I have no idea how to find the internal arc. I am thinking I will just cover all the connections with liquid electric tape on the inside, and hope it stops the internal arc.

Any suggestions?

[jimmy101]

The stun gun is supposed to have an internal arc, that's part of the HV circuit. It may have developed an arc where there isn't supposed to be one, or the one that is supposed to be there has failed and the high pitch tone you hear is just the oscillator.

Cheapo stun guns really aren't designed to ever be fired. They die pretty quick with use. Take it apart and (carefully) look for the internal spark gap, often it is just two pieces of sheet metal that cross each other with a small gap in between.

Based on the photos of that stun gun on the web it looks like it is actually in the range of 10KV to 30KV since the back-up gap is only about one centimeter.

Will it still spark across a gap shorter than the normal back-up gap?

[Kissmabass]

No it won't spark across no matter what. I contacted the company and they are sending me another free of charge, i'll see what happens. When I get the new one would it be possible to coat the whole inside with liquid electric tape, so there is no chance a stray gap can form?

"Take it apart and (carefully) look for the internal spark gap, often it is just two pieces of sheet metal that cross each other with a small gap in between."

I took it apart and couldn't find anything like this part described, I know what it looks like because I saw a picture of an internal spark gap online for another stun gun.

[jimmy101]

Post a picture or two of the guts. It is always nice to have more examples of the wide range of stun gun designs. And, perhaps someone can spot the problem.

I don't think coating the guts with "liquid electrical tape" will do much. If the internal gap isn't the problem then it is likely a burned out capacitor, coil or transistor. Electronics really don't like operating at tens of kilovolts. It is possible to make robust and reliable circuits for that voltage range but not for $10.