Jingle Bell Rock, on a Musical Tesla Coil

Jingle Bell Rock played on my own musical Tesla Coil, the Kaizer DRSSTC 2 Tesla Coil using the USB MIDI Stick interrupter. “Jingle Bell Rock” …

Musical Tesla Coil with Tmax USB MIDI Stick

TMAX YouTube: https://www.youtube.com/channel/UCjzHB0f_nxv_XY8Z9P1BklQ TMAX website: https://tmax-electronics.de/projects/ GitHub: https://github.com/TMaxElectronics Not a paid promotion! I bought these from my own money. 1-2 channel Compact USB MIDI Stick: …

Portal – Still Alive, on a Musical Tesla Coil

Played on my own DRSSTC2 Tesla Coil: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-ii/ Learn how to build your own DRSSTC to play music: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/ MIDI/Music interrupters you can build yourself: …

Star Wars – Imperial Death March, on a Musical Tesla Coil

Played on my own DRSSTC2 Tesla Coil: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-ii/ Learn how to build your own DRSSTC to play music: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/ MIDI/Music interrupters you can build yourself: …

Doom 2 – Readme, on a Musical Tesla Coil

Played on my own DRSSTC2 Tesla Coil: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-ii/ Learn how to build your own DRSSTC to play music: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/ MIDI/Music interrupters you can build yourself: …

3 new MIDI videos with Kaizer DRSSTC1

Ghostbusters theme “Ghostbusters” is a song written by Ray Parker Jr. as the theme to the film of the same name starring Bill Murray, Dan Aykroyd, Harold Ramis, and Ernie Hudson. The Buggles …

3x MIDI videos from DRSSTC1 demonstration

3 well-known classic songs are played with lightning on my medium sized Tesla coil, if you want to play these songs yourself you can find …

24 kV Marx generator

Introduction

This was my first high voltage circuit that eventually led me into building other high voltage generators, supplies and Tesla coils.

A Marx generator works by the principle of charging up a number of capacitors in parallel and when the voltage is high enough to break down the spark gaps, the capacitors will be discharged in series. When a Marx generator fires, it is said to be erected.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

Considerations

A Marx generator can work as a electromagnetic pulse generator, at high energy levels, if it is not shielded and grounded correctly. You can risk damaging electronic equipment if this circuit is not constructed or operated in a safe manner with these precautions in mind.

In the construction of the Marx generator it is very important to give great thought to distances that works as insulation between stages and components. An advantage against spark gap jitter can be achieved easily and for free by designing all the spark gap in one line where they can see each other. The UV light from the first spark gap will help break down the following spark gap and so forth.

The ideal Marx generator circuit will deliver n times the input voltage with n stages. So with a 4 kV supply and 6 stages, ideally I should have 24 kV output.

Each stage of 1 nF is charged to 4 kV and gives me 0.008 Joule energy per stage. With all 6 stages in series the capacitance is now 1/6 and the voltage is 6 times higher. So the erected capacitance is now 167 pF with 24 kV across it resulting in 0.048 Joule discharge energy.

 

Specifications

Voltage supply 4 kV at 20 mA / 20 kHz from a solid state neon sign transformer.
Stage design 6 stages of 2x 1M5 3500 V charging resistors and 1 nF 7500V capacitors
Discharge 24 kV at 0.048 Joule
Longest arc 20 mm sparks

Schematic

 

Construction

14th April 2008

The 4 kV supply used is a solid state neon sign transformer that delivers 20 mA. The output comes at 20 kHz from the switching and normally is no problem for a neon tube, but I need to rectify it to use it in the Marx generator as DC supply is needed. A string of 10 1N4007 diodes are used for a 10 kV rectifying diode.

3500V 1M5 metal-oxide resistors were used with two in series for each stage and 1 nF 7500V ceramic capacitors, this gave a good head room for a 4 kV stage voltage.

The long leads on the capacitors were used as the spark gap by soldering them to the string of resistors as far up the legs as possible and then bending them into forming spark gaps.

 

Conclusion

A Marx generator in this size and level of supply voltage is a very forgiving and hard to break circuit. This makes it perfect as a entry level circuit for high voltage experiments.

The few number of components makes it cheap and it is easy to source the high voltage capacitors on Ebay.

The sparks generated from the Marx generator is very loud and it is easy to gain higher voltages and thus longer sparks by just adding more stages. A circuit that is easy to upscale just by adding more stages and where output is quickly calculated with number of stages.

Definitely a must-build circuit for everyone with a interest in high voltage generation and experimentation.

 

Demonstration

28th April 2008

4000 Joule capacitor bank

Introduction

The idea behind a capacitor bank is to charge up as much energy as possible to short circuit that energy through small coils, aluminium paper, steel wool, wire and a lot of other things that can conduct a electric current. The short circuit current is enormous for a very short time and that big amount of energy can turn the conducting paths material into vapour.

To get an idea about how much energy 4000 Joule is, here is a couple of examples.

A human heart consumes 1 Joule of energy per heartbeat.

4000 Joule could lit up a 60W light bulb for 66 seconds, using a low energy 11W bulb it could be lit for 6 minutes.

4000 Joule is just enough for cooking 50 gram of water, to bring it from 20 degree Celsius to 100 degree Celsius.

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

DANGER!: High energy discharges can be lethal, the amount of energy released overwhelms what a human limp or life can withstand.

Considerations

A long time have passed since I built my first capacitor bank, the 333 Joule microwave oven capacitor bank. Since then I wanted to build a larger, but these large capacitors does not turn up often at a reasonable price. Patience was all I needed before picking up a Maxwell energy discharge capacitor from ebay at 40 Euro. It is not a pulse discharge capacitor, but will be well up for the little wear it will see in this use.

When discharging a capacitor into a circuit with a inductance, which could also just be its own equivalent inductance, the voltage will ring between the capacitor and the inductive part of the circuit, resulting in voltage reversal which can be very harmful for the capacitor. There are many ways to counter this and some of them are complex and expensive, for now I will ensure that a part of the circuit will be a thinner wire, that will always explode, and thus cutting the circuit.

Wear and tear on spark gaps is highly dependent on the energy transfer taking place. It is not as much affected by very high peak currents or energy levels, but the charge in Coulombs. Using the capacitor energy calculator on this site shows you both values and you will quickly discover that a high capacity low voltage bank will have a high stored charge versus a low capacity high voltage bank, despite they have the same energy stored, the factor in stored charge is 10 times higher for the high capacity bank.

 

Specifications

High voltage supply 776 to 1855 VDC from two transformers in step up setup and a voltage doubler.
Capacity 2423uF
Full charge voltage 1800 VDC.
Stored energy 4050 Joule.
Stored charge 4.5 Coulombs.
Trigger mechanism Spring loaded spark gap switch.

Schematic

 

Calculations

Having a capacitor bank with a large capacitance, I found it attractive to be able to charge it to different energy levels without being forced to use a variac. Knowing the exact energy stored will also make analysis of the discharges more precise.

By using the multiply input voltage taps on the step down transformer with an input voltage of 230VAC I get a varying output that I put into a step up transformer where I use the 656VAC output tap. Doing this I get a output voltage range from the voltage doubler from 776 volt to 1855 Volt.

Voltage² (Volt) • capacity (Farad) • 0,5 = energy (Joule)

1855² • 0,002423 • 0,5 = 4168 joule

In the following table I have all the charge possibilities listed.

Voltage Energy Terminals
776 Volt 729 Joule 1 and 7
813 Volt 800 Joule 2 and 7
854 Volt 883 Joule 3 and 7
889 Volt 957 Joule 1 and 6
928 Volt 1043 Joule 2 and 6
970 Volt 1139 Joule 3 and 6
1028 Volt 1280 Joule 1 and 5
1067 Volt 1379 Joule 2 and 5
1123 Volt 1527 Joule 3 and 5
1855 Volt 4168 Joule 2 and 4

Construction

I wanted to as many of the parts I have already at hand and focus on using parts that are odd and will have a hard time to find a place in other projects. The first focus of this was on the power supply, looking through my stack of transformers I found two that could be used for a step up transformer arrangement with the possibility of lowering the charge voltage as described above under calculations.

Capacitors and diodes for the voltage doubler is all salvaged from old electronic equipment and is right about on the edge of their ratings. Each string of diodes can withstand 2400 volt and the capacitors can withstand 1800 volt. I hope my decision about the capacitors is good enough, I did it to use a minimum of components and still maintain a capacity large enough to smooth the DC properly.

The spring loaded spark gap switch and charger switch is a copy of the switch I built for the 333 joule capacitor bank. I was a little worried that the rather small construction was not good enough for roughly 12 times the energy. I reinforced the switch with some heavy copper pieces and larger gauge wires and mesh. The biggest advantage of this switch is that I avoid making a protective circuit for the charger as its completely disconnected when the capacitor discharges.

 

Shot record

In order to keep track of capacitor lifespan, here is a list of the different shots that have been made with it.

100 Joule 3x steel wool + 1 Ohm resistor
300 Joule 2x steel wool + 1 Ohm resistor
700 Joule 2x 10 strands of AWG40
1000 Joule 8x steel wool
1x 200cm 0.25mm copper wire
4000 Joule 4x steel wool
1x iPod
1x C10A miniature breaker

Crushed cans, sparks and explosions

Steel wool

5th August 2012

The was the first test shot, 1 kJ into a small twist of steel wool.

 

11th August 2012

The current measurements was done with a Pearson current monitor model 101 connected to a 10x probe and a Rigol DS1052e oscilloscope. Attenuation on the oscilloscope was set to 1x. So numbers should be multiplied by 10.

Current measurements of steel wool, 60 mm length, 10 mm diameter, with 1 kJ energy discharged. Measured peak current 13 kA.

 

Current measurements of steel wool, 60 mm length, 10 mm diameter, with 4 kJ energy discharged. Measured peak current 29 kA.

 

A close up of the trigger spark gap doing a shot and the wear caused to it from about 10 high energy shots.

 

Conclusion

Having only fired the capacitor bank once, at 1 kJ, it is a little early to draw any other conclusions than it works as planned and its an ear deafening loud blast when it fires.

Having now conducted a 4 kJ shot, I can only say that it is a far as one should go with energy discharges in a small room. Feeling the pressure wave from the blast is the point where this continues outside.

Having measured 29 kA through a piece of steel wool makes me very satisfied with this capacitor, it is around 3 times more than I expected from this. Further measurements of short circuits through heavy conductors show level of around 25kA to 30kA.

 

Demonstration

5th August 2012 – 1 kJ shot into steel wool

19th October 2014 – 4kJ shot into steel wool

19th October 2014 – 1kJ shot into 200 cm 0.25 mm copper wire

19th October 2014 – 4kJ shot into a iPod

19th October 2014 – 4kJ shot through a Mini circuit breaker (SEKO DZ47-63 C10 1P+N)

Kaizer SGTC I

Introduction

This Tesla coil is my first and was build without any expenses worth mentioning, its the prototype from which I learned a lot about Spark Gap Tesla Coils, high voltage and where to find components in household items and trash.

In the development the first version was more of a proof-of-concept model build only from old microwave ovens, televisions and cable.

Mathematics and theory was not the leading part of this project in the start, but as optimizing went on I learned about tuning the Tesla coil for a better output, resulting in longer sparks.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

There is no protection against RF spikes going back into the High voltage supply and destroying it. 

The secondary coil is limited by the amount of copper wire I had available from the cooling fan motor from a microwave oven. The diameter / height ratio of the secondary is far from optimal.

I used my flyback transformer as the power supply, it have a very limited current at about 1mA at 20kV, roughly estimated.

In the start I used home made salt water capacitors which are far from optimal.

 

Specifications

High voltage supply20 kV from a flyback transformer
Primary capacitor
8 nF MICA
Primary coilinner 45 mm, outer 90 mm diameter, 1.78 mm diameter isolated copper wire, 6.6 turns.
Secondary coil50 mm diameter, 113 mm long, 800 windings, 0.127 mm enamelled copper wire.
Resonant frequencyTuned at around 655 kHz.
Topload60 mm diameter sphere, tennis ball wrapped in aluminium foil.
Input powerAround 20 – 30 Watt
Spark lengthup to 105 mm long sparks.

 

Schematic

 

Construction

10th May 2008

The secondary coil was wound on a plastic tube, 50mm in diameter and 160mm in height. Its bottom was conical so practically there could only be wound wire on 110mm of the height.

The copper wire had a diameter of 0.127mm, varnished its diameter is 0.14mm, this very thin wire made it hard to wound nicely without overlaps.

It took me 2 days to wound the secondary coil, it was hard on the eye, arms and hand to do in one stretch. The plastic tube was mounted on a gear motor controlled by a frequency inverter so I could control the speed by a potentiometer.

11th May 2008

To keep the windings in place and insulate the coil it was varnished with common ship varnish, it was given a layer in the morning and one more in the evening.

12th May 2008

As the power supply I used my 20kV flyback transformer driver at 12Vdc input, the capacitor is a home made salt water capacitor with a capacitance of 2.7nF. The primary coil was wound of ordinary 2.5mm2 wire around a cut up soda bottle.

The topload is a sphere made of bobble wrap, tape and aluminium foil.

Spark gap is just 2 copper wires.

In the first test I could get 4-5mm sparks to a grounded object, the biggest problem was the too tight coupling between primary and secondary. Too tight coupling resulted in alot of racing sparks on the secondary coil, these are dangerous as they can destroy the thin wire on the secondary coil.

Here is a picture of some racing sparks I provoked to get a picture of it.

The primary coil was wound in a bundle and by adjusting the height of it, the coupling could be changed. It was now possible for 40mm sparks to jump to a fluorescent light hold in my hand.

15th May 2008

varnish, varnish, varnish, varnish, glue, glue and more capacitance…

The flyback transformer driver runs at 12Vdc input.

I made another salt water capacitor and installed it in parallel with the other, the total capacitance was now 5.9nF.

As it can be seen in the pictures there is sparks or just “violet light” coming from other parts than the topload of the Tesla coil, its corona loss and decreases the spark length.

To isolate the secondary coil further it was given 4 more layers of varnish and the top of it was glued all over with hot glue. The metal cap was the new topload and 54mm sparks could be achieved.

28th May 2008

The flyback transformer driver runs at 17Vdc input.

85mm sparks can now jump to my fluorescent light.

The bottom from a beer can is the new topload, it results in some spectacular pictures, the higher voltage on the flyback transformer driver is the best improvement towards longer sparks, but also racing sparks on the secondary starts reappearing.

As it can be seen in the picture taken in the dark, there is still corona losses, and with this particular coil it will be impossible to avoid it at these driver input voltages. It is not easy to insulate 100kV. The following picture is taken with long exposure to show the corona around the coil itself, unfortunately its not as clear in the picture as seeing it live. The violet field around the coil is faint, but can be seen in the picture.

This picture is taken directly above the Tesla coils topload.

21st June 2008

I bought 10 old high voltage capacitors at 150 dkr (25$) for the lot, a real bargain in Denmark compared to the joy it has brought me. I only use one of them instead of the 2 salt water capacitors. Its a Fribourg Condensateurs from 1961, 8nF rated for 20kV pulse driving at maximum 2MHz.

A new topload was made from a tennis ball wrapped in aluminium foil, its not as smooth a surface as it should be, but it works.

The spark gap now consists of 2x WT20 tungsten welding electrodes, these are able of withstanding high temperatures without vaporizing as the copper wires were likely to do over time. There is still room for improvement on the spark gap as its still just a single jump static spark gap.

By calculating the Tesla coil in JAVATC I tuned the circuits to theoretically be in resonance, but its only approximating as the construction is far from precise.

With the new improvements 105mm sparks will jump to a grounded wire.

I took a series of pictures with different exposure times. Sparks are about 90mm long.

In the next picture racing sparks can be seen at the top of the secondary windings, without a breakout point or something to jump to, the energy build up is too large for the coil and its under a huge stress.

 

Conclusion

This small project started as a proof-of-concept model, to see if the theory I had learned would work in practice. It has come a long way since I started on it almost 2 months ago.

I learned a lot more about the theory of the Spark Gap Tesla Coil, the maths behind tuning the circuits and the importance of planning the design before building. This is no surprise. So there have been spend a lot of time trying to optimize a Tesla coil build around a badly designed secondary coil, so the result will never be near optimal.

Despite all this, I am very satisfied with the results of 105mm sparks. There are several things to optimize in a final version of the Kaizer SGTC I, it would be a better spark gap, shorter and more suitable wires, shape of the primary coil and its coupling to the secondary and a topload with a smoother surface.

Demonstration

Kaizer SSTC III

Introduction

The idea was to build a very small and compact Tesla coil as a gift for my mother that works in various science classes for the lower grades in public school.

This driver circuit is very similar to the one used in Kaizer SSTC I. This time I have made a PCB containing both driver circuit and bridge.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

I knew this would get claustrophobic with so little space for a complete interrupter, driver and bridge.

Using the enclosure as the heat sink is the reason why a low break rate is chosen, to avoid excessive heating.

 

Specifications

Bridge2x IRFP460 MOSFETs in a half bridge configuration
Bridge supply230VAC directly from the wall, 4A rectifier bridge and 330uF smoothing capacitor
Primary coilRev 1: 55 mm diameter, 1.38 mm diameter isolated copper wire, 10 windings.Rev 2: 80 mm diameter, 1.38 mm diameter isolated copper wire, 10 windings.
Secondary coilRev 1: 50 mm diameter, 200 mm long, 1430 windings, 0.127 mm enamelled copper wire.Rev 2: 75 mm diameter, 165 mm long, 1500 windings, 0.1 mm enamelled copper wire.
Resonant frequencyRev 1: Self tuning at around 470kHz.Rev 2: Self tuning at around 180 kHz.
ToploadRev 1: Made of two bottoms from beer cans, 65mm diameter and 30mm in height.Rev 2: 45 x 152 mm turned aluminium toroid.
Input powerInterrupted mode: ?W at 230VAC input voltage.
Spark lengthRev 1: up to 140 mm long sparks.Rev 2: up to 250 mm long sparks.

 

Schematic and PCB files

PCB file for ExpressPCB

 

Construction

21st July 2009

I designed a compact single sided PCB that contains both driver and bridge section on a mere 65 x 75mm board. Here is newly etched board, traces are a bit shaky as I have drawn them all by hand.

The MOSFETs uses the enclosure as a heat sink, I sanded down the paint for metal contact and use pads to isolate between MOSFETs and enclosure.

BPS is kept low, but can be varied from 4 to 20 BPS, to avoid excessive heating as the enclosure is not an optimal heat sink.

In the bottom of the following picture you can see the bridge rectifier mounted to the enclosure and the input filter for 230VAC in. The red wires lead to the 330uF/400V smoothing capacitor and the 100nF/1600V Rifa capacitor is the DC blocking capacitor in the primary circuit.

The coil is connected directly to 230VAC without any kind of voltage regulation and also requires a external 12VDC supply for the driver.

Antenna and primary coil connections are temporary solutions for the sake of demonstrating the Tesla coil in working order. A fold out antenna from a small radio or such will be added later. Some kind of support with banana jacks with a secondary and primary coil mounted on will be added, to avoid wrong phasing of the primary coil.

Here the complete setup is size compared to a 330ml beer can

 

Sparks

Here is one of the more spectacular spark pictures I have taken, in my eyes it looks like a demon waving its arms over the head which also have a distinct face with glowing eyes and a open mouth, or maybe I am just seeing things from inhaling too much ozone 😀

24th July 2009

I borrowed a expensive macro lens for my Canon 350D camera and took some pictures with great details of the sparks, very sharp pictures!

 

Revision 2

1st August 2009

Doing a short demonstration I adjusted the antenna with my hand while the coil was running, this resulted in unstable oscillations and the bridge was short circuited. I am now replacing the destroyed MOSFETs and here I can feel the disadvantage of servicing on a compact design.

A new secondary coil is in the making, it is wider, shorter and have half the resonant frequency of the first. It will be fitted nicely on a piece of acrylic for a complete look.

19th August 2009

The new secondary is finished, it took me about 8 days to do the winding as it is very intensive to wind with such a thin wire. Keeping the wire tight, windings close to each other, not pulling the wire too hard from the spool, watch for jams and overlaps and it all have to be done with a bright light very close to get a good view.

It uses the topload from my VTTC I, a 45 x 152 mm aluminium toroid, with this it have a new resonant frequency around 180 kHz.

Top of secondary was filled with epoxy to insulate the brass bolt from the inside of the secondary and the bottom earth connection is fastened with a nylon bolt.

It is all fitted onto a piece of acrylic with additional protection around the primary connections so it no longer possible to touch any conducting part of the primary circuit.

 

Audio modulation

I use a audio modulator made by the user Reaching (Martin Ebbefeld) from 4hv.org.

For sound input I use a cheap children’s keyboard from a toy store, its far from perfect for the job, especially because its waveform is highly distorted and its not clean tones but seems to involve a lot of modulation inside it to simulate different instruments. But its cheap and expendable.

Watch the film and look at the schematics for more about the audio modulation.

Conclusion

I am very satisfied with the final result, that I got to fit everything and use the enclosure as a heat sink turned out real good. Heating is not a problem with run times at about 2-3 minutes which is also the durations its been built to be demonstrated for.

Enclosure dimensions are 125W x 80D x 50H mm.

Revision 2 looks even better, performs better but was also a lot of work to wind the new secondary with such a thin wire.

Demonstration

Revision 1

Revision 2

Mazilli ZVS flyback driver

Introduction

The Mazilli ZVS flyback driver is well-known throughout the high voltage community for its simplicity and ability to deliver 20-50 kV at high currents for a flyback transformer.

I build this circuit almost a year ago on a vero board, but it kept blowing the thin traces due to high currents flowing. I eventually put the project in a box and forgot all about it.

Inspired by the point to point soldered designs Myke from the 4hv.org forums often uses, I tried to make something in that manner, not as pretty as his work though.

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

Considerations

The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150 mΩ

5 + 5 primary windings are suitable for voltages between 10 to 40 VDC, at higher voltages additional windings will be needed. Experiment with the number of windings to improve performance. Too few windings will result in excessive heating and too many will result in reduced power output.

A MMC is made from 6 capacitors to avoid excessive heating in a single capacitor.

This driver will push as much power as it can, so be sure to use flyback transformers that can handle the abuse if you want it to live.

 

Specifications

Voltage supply 35 VDC from a rewound microwave oven transformer.
MMC 0.66 uF from series string of 3x 2 275VAC MKP X2 capacitors in parallel .
Power consumption 400 Watt.
Longest arc 100 – 110 mm long white arcs

Schematic

Construction

15th may 2009

I have now rebuild the driver using 2.5mm² / 14AWG wire for a good current ability, larger heat sinks and a MMC to avoid as much heating as possible.

Sparks

16th may 2009

I found 4 different flyback transformers from my collection, among these are a 1980’s Bang & Ollufsen television flyback. A small flyback from a photocopier. A  flyback from a 1990’s portable television, it is without screen and focus resistor networks. A flyback with rectifier tube from a black & white 1950’s television.

The pictures with long arcs about the size of  100 – 110 mm was made with the 1980’s Bang & Ollufsen flyback transformer.

Conclusion

It was well worth it to rebuild this driver. It can now handle long run times with little heating despite pushing out around 400 Watt  of power!

Demonstration

Kaizer SSTC II

Introduction

This is a modified version of the first SSTC I built, the Kaizer SSTC I. It uses the same secondary, topload and driver board. New things is a full bridge of IRFP460 MOSFETs, audio modulation, shielded drivers and a new casing.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

In the quest for longer sparks I decided to use a full bridge to take advantage of the full voltage on the bridge.

The MOSFETs will be mounted on top of a heat sink so its easy to change them by only removing the secondary platform and solder them off.

The drivers will be shielded in order to avoid the EM field generated by the Tesla coil itself to inject noise into the drivers.

 

Specifications

Bridge 4x IRFP460 MOSFETs in a full bridge configuration.
Bridge supply 0 – 260 VAC from a variac, 8 A rectifier bridge and 1500 uF smoothing capacitor.0 – 365 VDC on the bridge.
Primary coil 115 mm diameter, 1.78 mm diameter isolated copper wire, 8 windings.
Secondary coil 110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire.
Resonant frequency Self tuning at around 250 kHz.
Topload 100 mm small diameter, 240 mm large diameter, toroid.
Input power Continues Wave mode: 2000 – 4000 Watt at 200 VAC input voltage.
Interrupted mode: 100 – 2000 Watt at 260 VAC input voltage.
Audio modulated mode: 300 – 400 Watt at 150 VAC input voltage.
Spark length up to 475  mm long sparks.

 

Schematic

The UCC3732X are MOSFET driver ICs, one non-inverted output and the other inverted, in order to get a push-pull drive of the gate drive transformer. A gate driver IC can deliver the high peak currents needed to drive MOSFETs efficiently.

The 74HC14 is a inverting hex schmitt trigger, it is used to get a proper solid 0-5V square wave signal from signals that are not perfectly square, the antenna feedback can vary a lot in waveform and amplitude, the 74HC14 converts this to a clean drive signal for the MOSFET drivers.

All unused input pins of a 74HC14 has to be tied to ground, floating inputs and a noisy environment is a recipe for trouble. The noise can couple between the gates internally and make the whole IC not work properly.

The music modulator works by amplifying the audio signal in the LM741 and at the BC547 transistors. The 555 timer ensures that the signal length of the generated square wave is much shorter than the audio signal, in order to not have too long on-time and thus damage the MOSFETs / IGBTs from over-current.

 

Construction

15th March 2009

I took apart a 19″ LCD monitor and a 24″ CRT monitor, from these respective computer parts I salvaged a good piece of acrylic from the LCD monitor and a fairly sized heat sink from the CRT. I cut the acrylic in half for a 2 level platform and the heat sink was cut in 4, its necessary to isolate the MOSFETs from each other as their housing is also a conductor.

19th March 2009

Driver electronics and audio modulator are installed under a metal casing from the CRT monitor to shield it from the heavy EM field surrounding the Tesla coil, this is to avoid problems with the driver being interrupted by its own EM field.

The bridge is made out of four IRFP460 MOSFETs, four MUR1560 diodes, four 5R resistors. The power supply is a 8 A rectifier bridge with a BHC 1500 uF/450 V smoothing capacitor, a 27K 7W bleeder resistor is added in the final build.

The audio in jack was later removed due to it making a short through its metal housing to the ground rail, I had overlooked that the audio in negative was not common with the ground rail, but there is a capacitor inbetween.

The secondary is held in place by a crate for ventilation on houses, its an easy and quick way of taking the coil apart for transport or storage, and it holds the secondary firm and tight.

A acrylic tube is added to support the antenna, in this way it is possible to adjust the coupling of the antenna to the secondary simply by pulling the wire.

The new shielding of the audio in signal is made from a piece of shielding from a industrial cable pulled over it and grounded.

The secondary with terminations. 110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire.

The complete coil looks, except maybe the electrical tape used to hold the topload together.

 

Sparks

Interrupted mode

At 250 VAC input voltage, 350 VDC on the bridge, it was possible to reach 475 mm long sparks, in interrupted mode, to a grounded object.

More pictures of sparks in interrupted mode, it is running at about 4 – 5 BPS.

3rd May 2009

Continues Wave mode

At 200 VAC input voltage, 280 VDC on the bridge and a power consumption around 10 A, peaking at 20 A, the coil was drawing somewhere in between 2000 to 4000 Watt. This resulted in very hot, thick white arcs punishing the dead iPod shuffle which remarkably left the player relatively unharmed considered what had just taken place.

These flame like sparks are 250 mm in length.

18th August 2009

I constructed a new topload from two cheap aluminium frying pans from Ikea. With handles cut off and screw from it grinded away it had a smooth surface and was fixed with a long screw through both of them.

6th September 2009

During a run of CW at full input voltage, the full bridge blew apart completely, with a loud bang.

 

Audio modulation

I use a audio modulator made by the user Reaching (Martin Ebbefeld) from 4hv.org.

For sound input I use a cheap children’s keyboard from a toy store, its far from perfect for the job, especially because its waveform is highly distorted and its not clean tones but seems to involve a lot of modulation inside it to simulate different instruments. But its cheap and expendable.

Watch the film and look at the schematics for more about the audio modulation.

 

Conclusion

Upgrading the SSTC I with a full bridge was a absolute must. It is small changes compared to the better performance and the driver have no problems at all driving four MOSFETs instead of just two.

Getting sparks at 475 mm length in interrupted mode and white power arcs at 250 mm length is truly satisfying for this little coil, the secondary winding itself is only 275 mm in height in comparison.

Enjoy the demonstration.

 

Demonstration

Demonstration of different modes.

New topload, running in interrupted mode.

New topload, running in CW mode.

New topload, running in interrupted mode and closeup of sparks.

Kaizer SSTC I

Introduction

This is my first solid state Tesla coil, so I went with a sturdy and proven schematic made by Steve Ward. A lot of other coilers have replicated this circuit with great success and therefore it is easy to find information how it works and how to troubleshoot it.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

One of the differences from the original circuit is that I use 230VAC input instead of 115VAC. So capacitors and MOSFETs have a higher voltage rating.

The interrupter will be changed to go down to a very low break rate.

 

Specifications

Bridge 2x IRFP460s MOSFETs in a half bridge configuration
Bridge supply 0 – 230VAC from a variac, 8A rectifier bridge and 330uF smoothing capacitor0 – 325VDC on the bridge.
Primary coil 115 mm diameter, 1.78 mm diameter isolated copper wire, 10 windings.
Secondary coil 110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire.
Resonant frequency Self tuning at around 250 kHz.
Topload 100 mm small diameter, 240 mm large diameter, toroid.
Input power Continues Wave mode: 1000 W at 230VAC input voltage.
Spark length up to 250 mm long sparks running interrupted.

 

Schematic

All unused input pins of a 74HC14 has to be tied to ground, floating inputs and a noisy environment is a recipe for trouble. The noise can couple between the gates internally and make the whole IC not work properly.

 

Construction

22nd January 2009

I began the construction of the half bridge circuit in a small plastic box, the heat sinks are a Pentium II heat sink cut in half. The bridge is made from copper wire size 2.5mm² / AWG14.

The bridge is made from a 8A bridge rectifier with 330uF 450V smoothing capacitor, two IRFP460 MOSFETs with MUR1560 diodes, two 0.68 uF 400VAC film capacitors for the voltage splitter and 10R gate resistors.

The driver circuit is made on vero board with a external 12VDC power supply.

 

Troubleshooting

23rd January 2009

When I first tried to run the driver circuit separately to test the driver before connecting it to the MOSFETs, it only resulted in the MOSFET driver chips (UCC37321/UCC37322) catching fire and burning up like a small volcano. This did of course upset me when it happened once more when I had changed the chips. This led me to seek help and I learned that running the driver chips unloaded, without a MOSFET or GDT connected to the outputs, the chips will oscillate into oblivion and burn them self down.

With the complete circuit put together it all worked except the primary coil was phased wrong, but it was no problem since I used banana plugs for the primary connections.

I ran the coil as CW (Continues Wave, non interrupted so its switching at its resonant frequency) to stress it to its maximum, which also did result in failures at 230VAC in, drawing around 4 to 5A.

The secondary coil was grounded to the mains ground in my house, but by accident I were using a plug without a earth connection in, so the secondary earth was arcing to the phase and neutral in my power bar. Pushing around 1 kW into this rather small circuit with passive cooling became enough combined with HF noise on the phase and neutral and one of the MOSFETs exploded violently and the other died silently. Here I discovered my design did not make it easy to change the MOSFETs, a important thing to consider in future constructions.

For the next couple of days I could not get the coil to work again. Everything in the driver circuit was changed and measured with a oscilloscope without finding anything out of order. It was first when I by accident measured short circuit connections with a DMM that I discovered one of the secondary windings on the GDT was not connected to the MOSFET, it was because the gate resistor was destroyed from the short circuit of the MOSFETs. Changing the 10R resistor made the whole thing work like a charm again.

 

Sparks

Here are some pictures from the first light, input power is from 30VAC to 230VAC at up to 5A.

 

Audio modulation

I use a audio modulator made by the user Reaching (Martin Ebbefeld) from 4hv.org.

For sound input I use a cheap children’s keyboard from a toy store, its far from perfect for the job, especially because its waveform is highly distorted and its not clean tones but seems to involve a lot of modulation inside it to simulate different instruments. But its cheap and expendable.

Watch the film and look at the schematics for more about the audio modulation.

 

Conclusion

Building this clone of Steve Wards SSTC5 was a great introduction to solid state Tesla coils, I now have a understanding of how it works from interrupter to driver to bridge.

Further projects with this circuit will be a complete rebuild with audio modulator and a full bridge of MOSFETs, this will be a separate project.

 

Demonstration

In thew following videos, the SSTC I is playing music from the interrupter shown in schematic for the SSTC II.

333 Joule MOC capacitor bank

Introduction

The idea behind a capacitor bank is to charge up as much energy as possible to short circuit that energy through small coils, aluminium paper, steel wool, wire and a lot of other things that can conduct a electric current. The short circuit current is enormous for a very short time and that big amount of energy can turn the conducting paths material into vapour.

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

DANGER!: Microwave oven transformers are a high voltage supply without current limiting.

Considerations

Microwave oven capacitors capacity is relatively low for their voltage rating, but they are designed to be applied around 300% of their rated DC voltage for 60 seconds. Most are rated 2100VAC at about 0,8 to 1 uF capacity.

A typical data sheet for a common microwave oven capacitor is as follow.

Technical Specifications Values
Capacitance 0.8 ~ 1.2 uF. +/-3%
Rated Voltage 2,100 VAC
Frequency 50/60 Hz.
Dissipation Factor 0.0035 maximum
Operating Temperature =”-10 ~ +85 C.”
Insulation Resistance : T- C 1,000 MOhms
Test Voltage: T – T T – T: 9,030 VDC for 60 seconds
Test Voltage: T – C T – C: 9000 VAC 10seconds

Microwave oven capacitors got a built in bleeder resistor which discharges the capacitor fast, which is why its important to discharge the bank as fast as possible when the wanted voltage is stored over the bank. On the other hand its a good safety feature that the bank will discharge itself within 30 seconds and that might save your life.

The amount of microwave ovens needed to build this bank is over the edge, but as they can be obtained for free from containers its still worth the time for the sake of the experiments.

All the critical parts in this project comes from microwave ovens and therefore it can be build with very little spend on materials.

Microwave oven capacitors are not build to sustain these hard short circuits, so they will take damage for each short circuit in the form of lowered capacity as the dielectric material in the capacitor is damaged, this might end fatal with a shorted capacitor that in the worst case will happen with a violent explosion. Take care to shield off the capacitors as they are housed in a metal can, fragments from these is not something you want flying around you if there is a failing capacitor.

Wear and tear on spark gaps is highly dependent on the energy transfer taking place. It is not as much affected by very high peak currents or energy levels, but the charge in Coulombs. Using the capacitor energy calculator on this site shows you both values and you will quickly discover that a high capacity low voltage bank will have a high stored charge versus a low capacity high voltage bank, despite they have the same energy stored, the factor in stored charge is 10 times higher for the high capacity bank.

 

Specifications

High voltage supply 6500 VDC from a single microwave oven transformer with a full wave voltage doubler.
Capacity 18.5 uF combined from 21 microwave oven capacitors in parallel.
Full charge voltage 6000 VDC.
Stored energy 333 Joule.
Stored charge 0.111 Coulombs.
Trigger mechanism Spring loaded spark gap trigger.

Schematic

Calculations

With the knowledge of the capacitors being designed to work with voltages 300% higher than their ratings for shorter periods of time, I have chosen to charge them to 6000 VDC as its convenient to build a charger for this voltage. This voltage can be achieved with a microwave transformer with a full-wave voltage doubler on the secondary side. The transformer delivers 2300VAC RMS.

2300Vac • √2 • 2 = 6505 VDC

The bleeder resistors in the capacitors loads the transformers and brings the voltage down to 6000VDC when its charging on the 21 capacitors my bank consists of.

The 21 capacitors are not the same make or capacity, but varies from 0,85 to 1 uF. I have measured the the capacity of the bank to be 18,5 uF with a LCR meter, the stored energy in the bank is then.

Voltage² (Volt) • capacity (Farad) • 0,5 = energy (Joule)

6000² • 0,0000185 • 0,5 = 333 joule

Construction

The capacitors are split into 3 strings with 7 capacitors in each. I soldered 4mm² copper wire between the terminals of the 7 capacitors and the 3 strings are connected with 6mm² wire bringing all 21 capacitors into a parallel coupling. Heavy gauge wire is used to ensure that it can withstand the huge current doing the short circuit and it gradually gets heavier the further into the connection towards the short circuit point we get. All connections are intended to be as round as possible to avoid corona losses when working with voltage into the kV range.

I build a wooden case that is split into 3 sections to separate the capacitors, charging circuit and dis- / charge mechanism.

As mentioned the capacitors got a built in bleed resistor which makes it crucial that the discharges happens very fast after charging is over. A solution could be to keep charging while discharging, but this poses new problems where we have to protect the charger circuit against the ringing current when the capacitors are short circuited.

I chose to make a spring loaded trigger that is pulled to the charger and when I let it go it springs to a brass plate where it short circuits the capacitors into the coil, look at the picture underneath and the schematics to get a better understanding.

 

Crushed cans, sparks and explosions

Now that everything is put together and calculations have been done to some extend, its time to harvest the sweet fruits in the shape of wonderful bangs, sparks and explosions. To get fully rewarded it is necessary to have some means of filming / take pictures of the sparks and explosions. A DSLR camera is by far the best for taking pictures with long exposure but there are great alternatives for Canon camera’s, its called CHDK. CHDK is a third party software that unlocks the power of the powerful processors in most of Canons digital compact cameras. Read more about CHDK.

Crushed cans

Winding a small coil with 3 windings of 2.5mm² hard copper wire, wound to fit a beer can tight, will make us able to crush a can with the very powerful and intense magnetic field that is generated when the capacitor bank is short circuited through the coil.

Aluminium paper

Short circuiting the capacitor bank through a small piece of aluminium paper will make it vaporize in a loud bang and very bright flash, it is hard to capture this properly as the light from the explosion is very bright and the aluminium paper burns up almost instantly.

Steel wool

The procedure is the same for steel wool as for aluminium paper, but steel burns slower than aluminium. It is possible to see the sparks with the naked eye, but the pictures of this is absolutely remarkable!

Water and fruit

You can see discharges primarily in water which results in loud explosions from the instantly vaporized water, the amount of steam developed expands very fast and that makes it so loud.

 

Conclusion

I am satisfied with the results I have achieved with a capacitor bank that was constructed almost for free as all materials come from things that were thrown out.

The steel wool sparks makes it worth all the work put into this project, and the dis- / charge mechanism turned out to be simple and effective.

Future improvements could count a higher charging voltage, if its raised to 8000VDC the bank would gain about 200j of energy.

Its important to use a work coil with large enough distance or isolation to avoid flash overs, this picture clearly shows what happens if this is not taken into consideration.

 

Demonstration

Kaizer VTTC I

Introduction

A VTTC is a Vacuum Tube Tesla Coil and it uses vacuum tubes / valves for the oscillator that is self biasing from a grid leak circuit.

I chose to build a VTTC because the operation and components were simple and few. It did turn out to be hard to find all the required components at a reasonable price in Denmark.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

After spending many evenings reading about vacuum tube Tesla coils and comparing tubes, I chose to build a Tesla coil utilizing two 811A transmitter tubes. These tubes have been used by others with great success, they are fairly cheap and have a moderate output power for a tabletop size Tesla coil.

Having studied and read about all the VTTCs I could find on the internet, it became clear to me that there are no pre written text book example on how to design your own VTTC from the bottom, as there do for other types of Tesla coils. Its about finding the old radio amateur books and manuals and combine some of the theory from those about oscillators and the knowledge gained by those who have build VTTCs.

The schematics for this dual 811A VTTC are by most people recognized as Steve Wards, but they do in fact go way back to a article from the magazine “Science Experimenter” fall 1963 issue, which are the drawings most dual 811A VTTCs are based on. I have not been able to find earlier material about this Tesla coil design.

I will build a Tesla coil that resembles the one Steve Ward build, in order to be able to compare the two coils. He succeeded in producing 180mm long sparks, due to it being his first VTTC he wrote there was room for improvement. I have tried to correct some of the issues he described and my goal was to achieve at least 200 mm long sparks. A major limitation to this project is money, so its being designed around components I have already available.

Here are some of the things I want to improve.

The high voltage supply needs to be able to exceed the maximum ratings of the tubes. For very short run times the tubes can be driven at a higher voltage / current than they are rated at, in order to achieve longer sparks.

The secondary coil will be bigger, from the unconfirmed theory saying that larger secondary coils gives longer sparks at the same power input in a VTTC.

Adding a Staccato controller to be able to adjust the break rate of the sparks, this will make me able to apply a higher voltage without excessive heating of the tuber, longer sparks can be achieved this way.

 

Specifications

Tubes 2x RCA 811A transmitter tubes
High voltage supply 230 / 2300VAC MOT with voltage doubler.
Supplied with 160VAC through a variac for 3200V.
Primary coil 180 mm diameter, 1.78 mm diameter copper wire, 26 windings, tapped at 22 windings.
Capacitor tank 4 nF Fribourg capacitor 20kV pulse rated.
Secondary coil 75 mm diameter, 440 mm long, 1600 windings, 0.25 mm enamelled copper wire.
Topload 45 mm small diameter, 152 mm large diameter, John Freud toroid.
Resonant frequency Around 300kHz.
Grid leak circuit 19 windings feedback coil, 1 nF capacitor and 500R to 2K5 grid leak resistor.
Input power 300W at 150V.
900W at 180V.
50W for the tubes heating.
Spark length up to 330mm long sparks.

 

Schematic

Here is the schematic with all the component values. Here is a few notes on choosing some of the components.

Tesla Coil circuit schematic

All ground connections are made at the same ground rail. R2 is a wire wound resistor with L4 wound around it, one for each tube. C4 is a decoupling capacitor mounted directly under the socket, one for each tube. R1 needs a high wattage rating, bigger is better, or supply sufficient cooling.

Staccato controller schematic. There are slight changes from the original schematics. I do not use a center-tapped transformer and have removed the polarity switch.

Here is the layout for a veroboard, green traces are the traces of the veroboard, remember to cut them where they do not join. Red traces are copper wire jumpers on the component side of the board. Notice that the red jumper next to D2 is connected to 14VAC in N along its way, this is the only jumper that does.

The ExpressPCB files for the PCB layout, however made for veroboard, can be downloaded here:

http://www.kaizerpowerelectronics.dk/wp-content/files/staccato.pcb

http://www.kaizerpowerelectronics.dk/wp-content/files/staccato_ver2.pcb

 

Calculations

Nearly all the following equations is originated from John Freau and is to be found in Steve Wards VTTC FAQ, there is a link at the end of this article. These calculations are not exact and will only work as a guide to building a system that is easier to tweak into good performance.

My goal with these calculations are to determine a Q value and a value for my tank capacitor.

First I will calculate the load impedance for my two 811A tubes. This equation is for class C amps supplied with AC or pulsed DC. If you want to calculate the tube impedance for a filtered DC supply use R = V / (2 * I) instead.

The maximum ICAS plate current rating for my RCA 811A tubes are 175 mA each.

R = V / (4 * I)

R = 3200 / (4 * 0.350) = 2285 Ohm

Next I want to find the primary reactance, f is my resonant frequency in Hertz and L is the primary inductance in Henry.

X = 2 * π * f * L

X = 2 * π * 300000 * (102 * 10^-6) = 192 Ohm

Now the Q value can be determined

Q = R / X

Q = 2285 / 192 = 11.72

Generally a Q of 10 to 20 is ideal. Lower Q gives less tube efficiency, more difficult coupling, but less tank losses. Higher Q gives higher tube efficiency, easier coupling, but more tank losses.

Now I can calculate the capacitance needed for my tank capacitor to work at the desired Q for the tubes I use. Result will be in nF.

C = (Q / (2 * π * f * R)) * 10^9

C = (11.72 / (2 * π * 300000 * 2285)) * 10^9 = 2.72 nF

The closest value capacitor suited for this high frequency and current was three 10 nF capacitors in series for 3.33 nF. The resulting Q for this tank capacitor value is as follows.

Q = 2 * π * f * R * C

Q = 2 * π * 300000 * 2285 * (3.33 * 10^-9) = 14.34

For my final tank capacitor I ended up using a 4 nF capacitor to only have one capacitor instead of a series connection of other types, this capacitor is intended for use in radio oscillators so it can handle the frequency and current, the losses are despite the higher Q value not enough to heat the tank capacitor. The resulting Q value for the 4 nF tank capacitor is as follows.

Q = 2 * π * 300000 * 2285 * (4 * 10^-9) = 17.23

 

Construction

14th July 2008 to 6th  August 2008

It takes its time to find all the special and at times rare components and materials at a price where I feel its worth it. It would take 1½ month to have found all the things that I needed.

The two 811A vacuum tubes are imported from USA through Ebay. Sockets and terminals are imported from England through Ebay. Heater transformer is bought from a private person in Denmark. The high voltage supply are from old microwave ovens with their capacitors and rectifiers. The rest of the components and materials are mostly thrown out stuff from various industry and private persons.

9th August 2008

The staccato controller is assembled on a breadboard and tested.

12th August 2008

The  staccato controller is build on a vero board.

30 – 31st August 2008

The secondary coil is wound and enamelled with 3 layers of varnish.

75 mm drainpipe with 1600 windings of 0.25 mm enamelled copper wire. End terminations are made from brass bolt and brass nut.

5th September 2008

A test setup have been build to experiment with the optimal number of windings on the primary and feedback coils, adjustable from 18 to 26 windings. With these options I can adjust the systems efficiency, frequency and coupling. In the first nights of testing 80 mm long sparks are achieved.

6th September 2008

The Tesla coil is tuned and adjusted

2300V high voltage supply, 1K/1nF grid leak circuit, 24 primary coil windings, capacitor tank 3.33nF.

160mm long sparks are achieved.

This is where I discover that my vacuum tubes are not conducting evenly, which they should as they were bought as a matched pair. I solved this problem by driving the weaker tube with 1 winding less on the grid leak coil, that was enough to adjust the screen voltage to a level where the tubes would conduct very close to matched conditions.

20th September 2008

A voltage doubler is added to the high voltage supply.

3200V high voltage supply, 3K/1 nF grid leak circuit, 24 primary coil windings, capacitor tank 3.33 nF.

260 mm long sparks are achieved.

3rd October 2008

3200V high voltage supply, 0.5K/1 nF grid leak circuit, 22 primary coil windings, capacitor tank 4 nF.

280 mm long sparks are achieved.

15th October 2008

The staccato controller is connected to the Tesla coil and it is now a completely different world, to modulate the sparks. It can vary the number of sparks per second from 1 to 50 outbreaks, the sound and shape of the sparks changes all the way through that scale.

Up to 330 mm long sparks can now be achieved through over driving the tubes further with a lower break rate.

27th October 2008

New clear PVC have been bought along with nylon supports for the primary, screws, shoes and fittings.

1st November 2008

Removing the isolation from 15 meters of 1.78 mm hard copper wire took a real long time as I need it to stay in its circle form. It did cost me a deep and violently bleeding cut to my thumb because I did not pay enough attention when cutting off the isolation. But I got the job done in all my bandages.

A platform was build from thrown out wood and clear PVC, that does not mean its not in good condition.

High voltage, filament and 12VDC transformers are placed on the platform, the capacitor is for the high voltage doubler.

All wiring is done, staccato controller added and the grid leak circuit is in place, everything is in its place.

 

Sparks

The complete coil in all its beauty, the blue and purple sparks go very well with the warm soft glow of the tubes.

This series of close up pictures really show the thin sword like sparks that are characteristic for a VTTC.

 

Demonstration

Running in CW mode.

Running in interrupted mode

Conclusion

The most important goal was to achieve at least 200 mm sparks and I went through the roof with sparks leaping out to 330mm.

I had assumed that the grid leak voltage would be so low that the coil could be wound on top of its own layers, but eventually it burned through and I had to find a place for the new grid leak coil wound in one layer. The 3 positions I had made for the grid leak coil in the nylon supports were no longer of any use unless I took the whole primary support apart and remade them, which I decided not to do.

The new grid leak coil is still made from 0.5 mm diameter enamelled copper wire, this is not optimal as its isolation is not thick enough, ideally normal wire with PVC isolation would be to prefer.

A higher Q value seems to be preferred if you have a tank capacitor that is able to withstand the heavier load.

Too much of the construction was not drawn in hand before building, that is a sure way to run into problems, but I built most of it from my head and took the battles along its construction, something that I do not advice others to do and I will try to avoid this in the future. 2D/3D CAD drawings would have been a great help, so for the future this will be standard in bigger projects.

 

Further reading

http://stevehv.4hv.org/VTTCindex.htm Steve Ward have documented 5 of his VTTCs, the staccato controller and written a good FAQ that is a must for anyone wanting to build a VTTC.

http://drspark.org/ Christopher Hooper have documented 3 of his VTTCs.

http://www.mif.pg.gda.pl/homepages/frank/vs.html Vacuum tube database, almost any tube data sheet can be found here.