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STOP PRESS  This is my old site last updated June 2005.  Enjoy the pics here but it is best to shift direct to the new site. Looks the same but lots more stuff and regularly updated.  The full size pictures  are only available there.

CLICK HERE to go to tesladownunder.com index page


My public displays include:

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Tesla coil (Scitech 2003) (on this page)

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Original coil

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Upgraded coil

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Specifications (original)

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Specifications (upgraded)

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Future plans

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Big Day Out (Syd Klinge's coil on tour in Australia Jan 2005)
 

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Magnetic levitation (Gravity discovery Centre 2004) (link to Magnetic Levitation page)
 

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Lifter (Gravity discovery Centre 2004) (link to High voltage/lifters page)

 Scitech is a non  profit organisation whose mission  is to increase interest and participation by Western Australians in science and modern technology.  It has been open since 1988 and has 250,000 visitors annually. 

My interest and involvement was sparked (pun intended) by its Tesla coil which was made by Stan Deyo in around 1988. It has functioned reliably with little modification since. The black and white double exposure publicity shot at the time is shown below on the left.

Original coil.  I was able to see the Tesla coil in Feb 2003, but found that it was not performing well with perhaps 2 foot streamers despite using a 5 KVA pole transformer.  Truly, here was a noble cause worthy of assistance. 

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The best picture I could get showing only small streamers (above right). Despite retuning, doubling the topload, and doubling the capacitance only about 3 foot sparks could be obtained.  The staff were keen to upgrade and I gave a demo of my 4 inch coil and micro wave oven transformer supply, which gave sparks up to 4 1/2 feet.

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On the wrong side of the Faraday cage (above), doing the demo in Feb 2003. An earthed PVC rod with steel wool on the end gives a sparkler effect if the sparks are hot enough. To the right in the photo is Scitech's TC which needs some work.

Upgraded coil. 

(click to enlarge)

In June 2003, my 6 inch coil was installed with a significant improvement in performance (above).  The sparks are now a lot hotter and are out to around 4 feet.  The length can be estimated by the 36 inch length of the secondary to the base of the toroid.  Still less than hoped for but a much noisier and more impressive display.

Specifications (original)
The original Scitech TC components included a 5KVA pole transformer 250 V to 12.5 KV with a soft start and extensive mains filtering and monitoring. It is ballasted with 3 paralleled heater elements which glow red hot after a minute or so of continuous operation.  It has fuse limiting to 16A.
The motor is an ARSG running on DC 180 V with 8 tungsten 1/2 inch rotating electrodes and 2 stationary. 
The 2 tank capacitors are each 20 nF mylar (total 40 nF at 20 kV). 
The previous primary was around 2-3 turns and the secondary is 6 x 30 inch with around 420 turns.
The topload was a 5 x 12 inch gold plated copper toroid.

The construction of this coil and the Faraday cage was of very high quality and the long service a testament to this.

Specifications (upgraded)

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The coil during modifications (above) with the new double layer primary and new secondary.  The double layer was needed to accommodate the larger number of primary turns (8 above, 5 below) in the same physical space as the previous 3 turn coil.
My changes were to:
          1  Replace the secondary with 6 x 32 inches with 1280 turns (previously 6 x 30 with 400 turns).
          2  Replace the primary now tapped at 8 of the 13 turns.
          3  Use a larger topload of a 12 x 29 inch toroid with a smaller 8 x 20 toroid beneath it.
          4  Add my Cornell Dubilier MMC capacitor of 45 nF to the existing capacitor (total 89 nF). 
          5  Run the motor from 200v DC (previously 180 V).
          6  Fit low profile strike rails.
          7  Use an inductive ballast (below) instead of the resistive one.

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The inductive ballast (above) made from a modified 440V to 240V transformer rated at 5 KVA bought at a junk yard. It weighs 30 kg and has a core iron cross section area of 47 cm2 (= 7.3 in2). The four 'C' cores were taken apart with gentle persuasion from a large hammer, and an 'air gap' made by using a cardboard or acrylic spacer between the cores. By using 0 to 6mm spacers the current draw on the 240 V winding can be adjusted from 1 A to 30 A. This corresponds to an inductance of 1.0 down to 0.04 Henries.
I plan to replace the resistive ballast with this inductive ballast soon. See Ritchie Burnett's site for comparative information.
The resonant charging capacitors (also shown above) of 74 uF is the sum of the 7 polypropylene capacitors that I had.  It is in series with the ballast and in parallel with the pole transformer.  Using these capacitors results in a higher voltage across the pole transformer input.  Testing with a 10 KVA transformer as a load with a 240V supply resulted in 280 V across the transformer with the capacitors compared with 195 V without. In other words this arrangement gives a higher voltage than the supply and will limit total current draw which generally sounds like a good thing.  In practice, however, it did not improved the performance or current draw and has been left out.

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Future plans
I have started to make some moves towards a higher current more reliable system and have been testing an EMI filter with two large ferrite transformers, 4 capacitors and 6 resistors.  It has been in my junk box for about 20 years (Golden rule: Never throw anything away).  I have tested it with 50 A resulting in a total of 200 W dissipation easily dealt with with a small fan.  I need to devise a simple control system that can be used without a variac and has a soft turn on a couple of seconds after the motor starts.  I am considering using inrush limiters to do this.
 

Big Day Out (Syd Klinge's coil on tour in Australia Jan 2005)
The Big Day Out is a rock concert that tours major Australian cities with over 40 , local and international bands. One of the side attractions (the main one for me) was Syd Klinges's 'Cauac' 16 foot coil running at 100KVA.   I was fortunate enough to meet Syd and his entourage and discuss coil details.   He runs from a portable generator rated at ?170 KVA 3 phase ?480V using if I recall correctly one 11 KV pig for each of the 3 phases each individually ballasted. The out put is rectified using over 1000 1N4007's to DC then through an RF filter to the base of the coil and the  spark gap which is ARSG using 1/2 inch tungsten electrodes.  Tank cap was two 0.1 uF custom made units.  Resonant frequency is 59 kHz.  The secondary is 10 feet tall and 16 feet total height. The winding is crosslinked PVC coated.  Toroid is chicken wire covered.

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Some shots of the day with attendance 44,000 in Melbourne.

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This page was last updated August 28, 2005