UK Teslathons


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Cambridge 2010

nig tesla coil cambridge 2010
Video link to Tesla coil on YouTube

Video link to Tesla coil on YouTube 2
With Breakout Point

Video link to Tesla coil on YouTube 3


With Breakout Point

Video link to Tesla coil on YouTube 4

Video link to Tesla coil on YouTube 5
With & Without Breakout Point

10 foot tesla coil arc

My High Point......Ten Foot +

A nice 10 foot+ strike (point to point straight line distance). (taken from a video)
The height of the toroid's break-out point had previously been measured at 74 inches high, while the distance to the strike screen (located to the right and horizontal to the toroid) measured 97 inches (8 foot 1 inch) in the horizontal plane.
After the video was analysed the coil was setup again to those measurements and using the image the exact strike point could easily be found and measured.

Phoenix tesla coil streamer

Once again, the city of Cambridge acted as a magnet to those with an interest in tesla coils, as for the eleventh time it hosted the annual (2010) Cambridge Teslathon.

I therefore decided to lug a lot of what is basically, copper wire, vinyl and heavy iron, 170 miles up the motorway network, swearing that I will never do it again, exactly as I had said last year, and, no doubt, as I will say again next year.

Phoenix tesla coil

My coil had recently had an extra 30nF added to the MMC, as has been explained Here, and this extra capacitance seemed to have improved the intensity and ferocity of the sparks.
I ran the coil initially with a break-out point and found no difficulty at all constantly hitting an earthed screen erected 8 feet away (measured distance)
Unfortunately the overhead lighting conduits were also at an 8+ foot distance and they acted as a limiter on what I could really achieve.

Most of the runs on the second day of this two-day event were done without a breakout point (BP). This changes considerably how the coil behaves at start-up. With a BP fitted, the coil would start to fire when the variac was inputting just 50V. (250v normal mains voltage - UK)

Without the BP fitted, I found the coil would only breakout when the input reached 200v to 210v. This shows how the now larger minor diameter of the new toroid was doing its job and holding back the charge till it was higher in value. When the coil did eventually break out, it was both violent and loud, like a firecracker going off.

big tesla coil
Phoenix tesla coil
The resonant frequency of the secondary was 81 kHz in the hall, as the overhead lighting conduit was having minimal effect on the frequency on this occasion. Whilst tuning the secondary with the oscilloscope I did find that once the display showed resonance (display shows maximum amplitude) that this could be altered by anyone approaching anything closer than eight or nine feet. This would also apply it seems to its vicinity to other objects, hence my concern about the overhead lighting conduit.
With my previous 6 x 24 inch toroid, you could approach within six feet without any effect. I presume from this behaviour that the larger toroid creates a much broader field.

I next ran a couple of artificial streamers from the toroid (bits of thin wire) to simulate the capacitance of real streamers and found that the frequency then dropped down to the region of 70 kHz, dependant on the streamer length.
I therefore tuned the primary to 70 kHz to allow for this. This meant the coil should be closely in tune when a streamer forms. Prior to that happening the tesla coil is obviously slightly out of tune, but it does not seem to be too critical of this, and in fact seems to benefit more by being in tune when a streamer is created.
Phoenix tesla coil


It was not an event entirely without incident however. At one time, a fluorescent lighting tube decided to commit suicide by falling on someone's head whilst they were filming a run of my coil.

The person though is the tesla coil world's equivalent of an 'Ambulance Chaser', as the first sign of any smoke will always be well documented on his website. (See Here for the gory details)

Prior to this, I had managed to badly burn the winding of the variac I use for the Phase Controller. This was caused it seems by a dirty contact between the wiper and its winding, creating a high resistance point that heated up. Fortunately, Derek (aka 'The Ambulance Chaser') came up with the simple solution of using the variac reversed. This was possible because in the arrangement for a phase controller, the variac is wired simply as a variable inductor. (See Phase Controller link at top).

Other Teslathons

Nottingham 2010

Cambridge 2009