dischargeschematicssparkvoltage
I recently got into eletronics, and there are some concepts I am having a hard time understanding. I was looking around youtube and saw this video of a small EMP generator, I understand the basics of it, the magnetic field inducts a current thus frying electronics, but what I'm interested in is why there is a spark gap in the schematics. What does it do ?
Maybe you could use a Shockley diode or DIAC model (NOT a Schottky diode). A Shockley diode turns on when the voltage across it reaches its breakdown voltage and doesn't turn off until the current though it falls below a minimum holding current level.
Here's a site that goes through creating a SPICE model: http://www.beigebag.com/case_shockley.htm
Usually cheap arc welders have difficulty being set to very low current.
Spot/resistance welders -there are good machines with specs like these (Miyachi):
This kind of machine is very expensive- probably $5-10K, and worth it for high tech manufacturing (we use them for making superconducting junctions).
There are very cheap welders sold from China for making battery packs, and some can be used with tungsten handheld probes. Not sure about well they work, however, caveat emptor. It's easy to find them, and you may recognize the type you saw.
Edit: Okay, John, that's a great video. Such dexterity- working with both hands simultaneously during the orientation phase of the operation! The 5mm spark you saw may be "HF" = High Frequency which is used to initiate the arc. Conceptually, there is a series choke which conducts the main arc well, but presents a high impedance to high frequencies allowing a high voltage to be superimposed on the low voltage welding supply. I think the operation shown in the video would not be very healthy if the solder was not RoHS- the temperatures in an arc could result in a lot of lead vapor compared to a soldering iron. Very fast though. As a buyer/factory inspector- plenty of places for human error in that process- at least the worker is wearing finger cots. You can expect the odd intermittent joint to slip through even with 100% testing. Ask them what their fallout rate is at testing and verify by looking at the size of the piles of reject units vs. production rates.
Best Answer
Presumably the high voltage converter is rectified and put through a multiplier, otherwise this circuit wouldn't work. The capacitors in the multiplier are charged up by the DC and when the voltage becomes high enough to jump the spark gap, all of the energy stored in the capacitor(s) is dumped into the coil, thus producing a powerful EMP. You can think of the setup as building up pressure until it reaches a certain point, and suddenly releases all of that pressure all at once. You can see how that would be much more powerful than simply passing the current through the coil.