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.
Australian safety requirements: The Dept of Energy Safety inspected my 'shed' on Nov 21, 2003. My equipment runs from 50 V AC to make it pass the Western Australian requirements. Higher voltages require a qualified electrician unless they are 'downstream' of the 50 V AC. This is provided by an arc welder stepping down the 240 V AC mains to 50 V AC (120 A peak). The 50 V AC is then stepped up (by another arc welder wired in reverse) to 240 V AC again. Actually 225 V with losses. Various projects then raise this voltage a lot further. Assume that all home made mains equipment described runs from this arrangement. Note that this is no safer, just legal or rather not covered well by existing laws.
My two arc welders showing 225 V output. The internal view of the smaller (110 A) welder showing the adjustable shunt giving variable current limiting.
Measurements: I have been a bit limited with the technical measurements but hope to add these as I obtain them. Of particular interest is the peak current to the coil gun and confirmation of the calculated tuning details for the TC. Any one care to donate a digital storage CRO? I have kept most measurements in inches and feet etc rather than our metric units for the benefit of US coilers. And yes we do spell aluminium like that in Australia.
I feel that many Tesla coil shots on the web are blurred, out of focus or are just don't convey the size of the sparks/streamers.
I have a list of criteria that I use for digital cameras (I did win an award for my cover shot on my site - well a small one anyway from ACD Systems Nov 2003 photo contest)
Glossary: (If you can't find it below, try here)
ARSG Asynchronous rotary spark gap. This switches the capacitors charge into the coil rapidly and frequently but not in synchrony with the mains 50Hz. In my case the rotary disc is driven by an angle grinder motor. See SRSG.
Ballast is a method of limiting otherwise excessive current draw from the mains particularly when using large transformers 'pole pigs'. Typically inductors (large coils) are used but in other situations, resistors or capacitors can be used.
Capacitor stores electrical charge and allows alternating current to pass. In its simplest form it has 2 conductive plates separated by an insulator. The main capacitor in a Tesla coil is the tank capacitor. This can be homemade (in my case with aluminium foil and polyethylene sheet) or by multiple mini capacitors (MMC). Other capacitors are used to filter voltage spikes or as power factor correction. The value is typically measured in microfarads (uF), nanofarads (nF) or picofarads (pF). The other main capacitor is the toroid although it might not look like one.
MMC multiple mini capacitors. In my case using 30 (or 60) polypropylene capacitors rated at 0.33 uF at 1600 VDC to obtain a total value of 0.044 uF (or 0.088 uF) at 24 kVDC. With this particular series of Cornel Dubillier capacitors it has been found that this DC rating can reasonably be used as the AC rating with Tesla coil use.
MOT Microwave oven transformer typically rated at 250 VAC in and 2000 VAC out at perhaps up to 1000W. Four of these are used in my supply.
MOV (metal oxide varistors) used to protect circuits from transients, such as across the mains to protect spikes of voltage above mains voltage.
NST Neon sign transformer. Typical rating 250 VAC in and 12,000 VAC out at 30mA.
Power factor correction capacitors are capacitors across the mains which improve the phase angle of currrent versus voltage and will reduce the apparent current draw of a transformer. Typically 30 uF for an NST.
RCD's (residual current devices) are a safety device on the mains that switch off power if more than typically 30mA is leaked to earth to prevent electric shock.
RQ (Richard Quick) static gap is a stationary spark gap for smaller Tesla coils using a number of short lengths of copper pipe nearly touching so that there are multiple small sparks in series.
SCR (silicon controlled rectifier) Is an electronic switching device in some respects like a large transistor. They can switch large amounts of power .
SRSG Synchronous rotary spark gap. This switches the capacitors charge into the coil rapidly and frequently in synchrony with the mains 50Hz. In my 18 inch coil this will be from a modified motor running at 3000 RPM. See ARSG.
Sparks What Tesla coils are all about. Lightning like high voltage discharge through air to another object.
Streamers Sparks that leave the toroid and branch off in to the air without reaching another object.
TC Really, you should work this one out for yourself.
Variac A variable 'autotransformer' used in the mains circuit used to vary the mains voltage (110 in USA, 250 in Aust) from 0 to full mains voltage up to about 110% i.e. 120 V / 270 V.
Ohms Law v (Volts) = i (current in Amps) * r (resistance in Ohms)
Power P (Watts) = v (Volts) * i (current in Amps)
Power P (Watts) = 1/2 C (capacitance in Farads) * v (volts)
Impedance Z (Ohms) = 2 * pi * F (freq in Hertz) * L (inductance in Henries)
Vsec = Vprimary * sqrt [
L sec / L primary]
More comprehensive and interesting safety information is here
2 A short cartoon (1.3 Mb)- must see : )
3 A sign on the outskirts of a nearby town. Many of my projects result in IONS - sparks, lasers etc. LIONS are a local service organisation but have lost part of their "L". I am probably the only person in the world that finds this even faintly amusing.
This page was last updated August 28, 2005