Tesla coil and DRSSTC frequently asked questions

Frequently asked questions

How to make a DRSSTC?

If you have never build a DRSSTC before, the best practice is to copy someone else’s proven design. There are many pits to fall in doing design, construction and testing that can be avoided by building a replicate of a working machine.

The experience gained from building a DRSSTC from a proven design can be used to build another later, where you can make changes to the design, use different parts, add other features etc.

The experience you now have after building a couple of DRSSTCs is enough to start designing your own from scratch, you now know enough of the founding ideas, what works and what does not, how to build optimized parts of the system and what it takes to push electronics beyond their rated limits.

 

Which skills do you need to make a DRSSTC?

Basic electronic knowledge is enough and the more advanced subjects can be learned along the way of reading, designing and building. Forums like http://www.4hv.org is a great place to ask for help. If you show interest, have done your research and ask for help on specific problems, there is all the help you could ever dream of.

You can use your hands and tools. Soldering is necessary and knowledge about using a oscilloscope. It is again skills that can be learned.

Be realistic about the time, money, space and power supply available to power a DRSSTC.

 

Which tools do you need to make a DRSSTC?

Regular tools: Screw drivers, pliers, cutter, hammer, saw etc.

Electronics tools: Soldering iron, multimeter and oscilloscope.

Nice to have: differential probe for isolated measurements with the oscilloscope, isolation transformer to be able to ground the negative rail of the power circuit when testing, industrial wideband current monitor to monitor primary current wave form.

 

How to tune a DRSSTC?

The best way to tune a DRSSTC is setting up exactly at the turn number that can be calculated with the wonderful calculator JavaTC.

To find the sweet spot, where sparks are the longest at full input voltage, detuning of the primary is used. When a spark of a certain length is flying output from the topload, this presents a load with a capacitance, this lowers the resonant frequency of the secondary coil. By tuning the primary circuit for a lower frequency than then secondary, the purpose is to find a lower resonant frequency of the primary circuit that corresponds to the loaded resonant frequency of the secondary circuit.

This topic is described in much more detail in the DRSSTC design guide chapter on tuning.

 

How big is a DRSSTC?

One thing that can come as a surprise is how large a DRSSTC system is when it is put together. It can all seem very handy when you are working on the different parts, but once it is assembled it can seem much bigger. Another practical issue with size and weight is if you can handle to put it together with just one person, maybe you need to be two to rise the secondary and mount topload and perhaps it is even needed to use lifting equipment for heavy weights.

  Small Medium Large XLarge
Power 400 W 2500 W 10 kW 25 kW
Peak current 280 A 800 A 2000 A 5000 A
Frequency 327 kHz 70 kHz 38 kHz 35 kHz
Weight 2 kg 30 kg 120 kg
Height 0.45 meter 1.2 meter 2.8 meter

 

How much does it cost to make a DRSSTC?

It all depends on how long you want to wait to find a specific part a good price. The listed prices in these tables are mostly second hand used items for the electronics and new for the mechanical parts. A good example is how I got a good deal on the CM600 IGBTs and not as good a deal on the CM300, they actually cost me more per brick.

Most of the listed parts below are found over a long period of time, so obtain parts at the best price possible.

Enclosure Scrap plexi
Cost: Free
Wood and wheels
Cost: 45 Euro
Wood and wheels
Cost: 120 Euro
         
Rectifier 1x 25A bridge
Cost: 2 Euro
2x 25A bridge
Cost: 4 Euro
3x 200A double modules
Cost: 10 Euro
Filter capacitor Scrap capacitors
Cost: Free
2x BHC 3300uF / 450V
Cost: 4 Euro
4x Siemens 6000uF / 350V
Cost: 10 Euro
 
Heat sink Scrap heat sink
Cost: Free
Small heat sink
Cost: 5 Euro
Large heat sink
Cost: 15 Euro
Switches 2x IXGN60N60
Cost: 28 Euro
2x CM300HA-24H
Cost: 100 Euro
2x CM600FA-24H
Cost: 62 Euro
8x MBI800-120
Cost:
Busbar 2,5 mm2 solid copper wire
Cost: 1 Euro
40 mm2 from 1,5 mm copper sheet
Cost: 12 Euro
300 mm2 from 10×30 mm copper
Cost: 25 Euro
Wiring PCB and wire
Cost: 1 Euro
6 mm2 wire
Cost: 10 Euro
3×35 mm2 wire
Cost: 30 Euro
         
Secondary wire 0.127 mm, 0.1 kg spool
Cost: 10 Euro
0.25 mm, 2.5 kg spool
Cost: 30 Euro
0.7 mm, 10 kg spool
Cost: 200 Euro
Secondary form 50×500 mm grey PVC
Cost: 3 Euro
160×1000 mm orange PVC
Cost: 31 Euro
315×3000 mm orange PVC
Cost: 200 Euro
Varnish Spray varnish
Cost: 10 Euro
0.5L varnish and brush
Cost: 33 Euro
0.75L varnish
Cost: 25 Euro
         
Topload Styrofoam and aluminium tape
Cost: 10 Euro
Wood, 127 mm alu ducting and alu tape
Cost: 40 Euro
6x laser cut alu holders, 7x rings of 25 mm coax cable
Cost: 340 Euro
         
Primary coil 2.5 mm2 solid copper wire
Cost: 2 Euro
10 meter of 10 mm copper tubing
Cost: 24 Euro
14 meter of 10 mm copper tubing
Cost: 34 Euro
MMC 2x 942C
Cost: 5 Euro
12x 942C
Cost: 32 Euro
5x 4uF/3kV GTO snubber capacitor
Cost: 266 Euro
         
Driver Universal driver 1.3
Cost: 15 Euro
Universal driver 1.3
Cost: 15 Euro
Universal driver 2.1
Cost: 25 Euro
GDT 1x ring core
Cost: 5 Euro
1x ring core
Cost: 5 Euro
2x ring core
Cost: 20 Euro
CT 2x ring core
Cost: 10 Euro
2x ring core
Cost: 10 Euro
2x ring core
Cost: 10 Euro
         
Total cost 103 Euro 400 Euro 1404 Euro

 

Where to find parts to build a DRSSTC?

Ebay is the best source of exotic parts like large IGBT bricks, large pulse power capacitors, electrolytic filter capacitors and snubber capacitors.

Look in your area for metal scrap yards, here you can often buy new materials that have been thrown out for reuse, at scrap metal price. This is a good place to source copper clad, busbar, copper tubing and other metal parts for construction.

You should also look for local HAM markets, those are flea markets by and for radio amateurs. Here you can usually find cheap power supplies, oscilloscopes and small parts. With a bit of luck you can also find power electronics and filter capacitors.

Varnished copper wire for the secondary coil can be found locally at motor or transformer winding companies. It can also be bought from electronic stores and ebay. Prices are about the same in all places due to it mostly being copper and is governed by the metal prices.

Secondary tubes, pipes and forms can be found in home depot shops ranging from 40 mm diameter to 160 mm diameter. Some times up to 200 mm can be found in the same places. 315 mm diameter pipe and large is usually only to be found through construction companies, wholesale or ordering online.

 

What does the different DRSSTC abbreviations mean?

DRSSTC – Dual Resonant Solid State Tesla Coil

MMC – Multi Mini Capacitor

BPS – Bangs Per Second

GDT – Gate Drive Transformer

CT – Current Transformer

FRES – Resonant frequency

 

 

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