Instructables

Cheap and portable >12V >10A PSU for small tesla coil? any good topload sugestions?

I am currently planning a small tesla coil (15 inches high, hopefully 5-12 inch sparks) I would like to make the unit small (desktop size). I decided to build the coil around a ZVS-driven flyback transformer rather than a standard NST or Oil burner transformer due to several advantages the ZVS circuit can offer: battery operation, smaller size, simpler math, no requirement to "match" the capacitance with the transformer, and since I have almost all the parts necessary to build another ZVS driver, why not!?

The ZVS driver drive a DC flyback at approximately 15KV, which will then charge a homemade capacitor (I will not invest in a true MMC because it will put stress on the capacitors and connections, not mentioning the price of better quality film capacitors.) I have determined the dielectric breakdown of a few household items (plastic wrap, lids, lunch bags, etc. I assume they are low-density polyethylene) with my ZVS singing arc assumed to be at 8-10KV, and figured one layer of 5x7 inch compressed between 8 layers of plastic wrap gives an approximate capacitance of 0.7nF (sitting flat on a table with a few books to compress the plates closer together) to 1.44nF (after being rolled up very tightly. However, the breakdown voltage of this may be too low. I have yet to test this with my singing arc project) 

The Capacitor will be several layers of plastic wrap sandwiched between layers of aluminum foil, which will be cut 3/4 inch shorter on all 4 sides, and after approximately 8-15 layers have been added, the capacitor will be sandwiched between 2 wooden boards with bolts on all 4 sides to permanently compress the capacitor to achieve approximately 10nF +- 5nF. This compression method might even help me fine-tune my tesla coil!  the aluminum plates will be tabbed, so that when they are stacked, the tabs will face opposite directions.  I might even submerge the capacitor in oil and pull a vacuum on it if I feel it will be necessary. However, I have not constructed a HV capacitor before, so I do not know how well this design will work. Does anyone have some experience in this matter?

And lastly, my Power supply section to power the project: Has anyone built a ZVS-based tesla coil here? I see them all over youtube, with outputs ranging from millimeters (similar to my slayer exciter project)  to over a foot long! However, they never state what their PSU is rated for, or use 12 Lead Acid batteries, which I feel would be a bit impractical.

So my question is: To get the output I desire, how many volts and amps should my power supply be rated for? I am thinking either a 24V 10A Switchmode supply from amazon, with the voltage adjust maxed out, or a 28V 10.8A SMPS, or a cheaper 24V 15A. SMPS. I thought about making a unregulated supply with a large transformer and a high-amperage full-wave bridge rectifier, but this cost more, and I cant be certain on it's quality. Can SMPS be used? can the amperage be below 10A? most importantly, does anyone have good data on current draw @ given voltages @ given # of turns on the inductor and flyback?

iceng8 months ago
Gorilla glass could be your capacitor insulator.

There has to be a dead iPhone4 that you could remove and test the breakdown voltage
of the back panel.

BTW Apple is setting up a huge sapphire glass plant in AR
Mayne that can be your future capacitor insulator separator.

A
-max- (author)  iceng8 months ago
Nice idea, but I think it would be overly expensive (many broken iphones cost more than plastic wrap or wax paper) Also, it would be too thick and small to achieve a reasonable capacitance, I had a hard time achieving 0.1nF with a thick plastic from a plastic container for food, surely, the Iphone screens are far to thick, and many would be required.