Here are some of the highlights of high voltage spark photos. For a gallery of Tesla sparks go to Tesla sparks.

           

Above left photo shows a 5 inch (12 cm) arc from a mobile x-ray supply. It is DC about 100 kV with a large capacitor but goes through a large HV resistor within the white tube. There is a large convoluted power arc that last about 1/2 second. The right photo shows a 26 inch arc from another larger x-ray transformer running about 40 kV. It only jumps just over an inch but like a Jacobs ladder just grew and kept rising.
Alternatively one can use SIDAC’s. This very simple circuit uses the transformer, capacitor and diode out of a microwave oven to supply 2000 VDC. Once the voltage rises to 2000 V the SIDAC’s fire dumping the energy into two ignition coils to give sparks of easily 5 cm. I am using 9 SIDAC’s each rated at 240 V 1 A RMS and 20 A pulse. Each is shunted with a 1 Mohm resistor to give more even voltage division. There is a 10 Kohm 10 W resistor used for these shots but power draw is triggering a 10A cutout and there is sufficient heating of resistor, diode and SIDAC’s to only allow short runs. 50 Kohm will allow about 4 sparks per second.

Unfortunately this is very hard on the ignition coil’s insulation. I have lost one coil but the remaining one still puts out 3 inches and also about 10 inches of surface tracking (below).

MOT supply in a MO. (Microwave oven transformer) 2004

The sparks when viewed end on are interesting. Or even when viewed close up….

                 

The left photo with the safety glasses was to get the reflection. My normal glasses have an efficient anti reflection filter. The right photo was a lot harder to arrange than I thought. To get a close up of a face and sparks in one shot with a reflection in an eye means a long exposure and F stop backed off all the way to 32. Almost a pinhole camera. The virtual distance of the reflected spark is so far away that it will be really out of focus and also so much smaller and fainter due to the convexity of the eyeball. So it meant a lot of sparks to get a blue blur on the corneal reflection. Without the reflection it looks photoshopped. I have to hold my eye open and be absolutely still for 10 seconds while loud IC sparks fire off in front of my line of vision.

The set up to have sparks in front of my eye. Having the spark closer is helpful but you can’t get a 2 inch spark closer than 2 inches to your nose. I was also a little worried about cumulative UV exposure to my eye with the many takes.

This is a standard screwdriver. It is interesting how the arc bends around it. This is because the hot arc channel is a low resistance but the air just next to the screwdriver is cold (or at least not not ionised and would have to be “jumped” by a sufficient voltage for it to connect. This only happens with stable pulsed DC or AC arcs. One could make up a bit of a pseudo-explanation for this and indeed I have on the 4HV community.

Related pages

External links

Try something else

Photo Date