More sparks

The OLTC II has now been tested a few more times, in the garden and at Alan Sharp's place in Burntisland.

Arcs to a ladder

At first, it was plagued by problems. The power seemed to be unstable and often it would trigger the crowbar and shut down completely whenever a streamer struck ground. That is why the arcs look dim in these pictures- I couldn't get it to stay running through the whole exposure.

No luck this time.

The dim streamer stretching down towards the bottom left is something like 53". (It may not show up on all monitors.)


Reworking the crowbar circuit made the problem less acute. (The crowbar sense resistors were unshielded and were obviously picking up EMI.) Having done this, modified the strike rail to remove a sharp edge that was causing flashover, and retuned slightly, it was able to break out without a breakout point.

But now a new problem reared its head. While testing the coil in Alan Sharp's church hall (thanks Alan) we found that as the power was increased towards the magic 1kV, the quenching would dither between first notch and notch-and-a-half :( This was obviously what had been causing the power to be unstable.

Debugging this was a hoot, since it only happened near full power, by which time the thing was shooting out 3 foot long arcs and the drive electronics were all floating at -300V. I ended up lying on the floor with my hands over my ears, watching a battery powered scope, safely (?) out of striking range. while Richie fired up the power supply. Luckily the church coffee morning was over by this point.

Much tweeking later, it was still misbehaving, but I thought I would just go ahead anyway. I set up a grounded target about 4ft away and attacked it with 2.5kW of power at 400bps. The result was these white-hot almost continuous arcs. Huh huh, Tesla coils are cool!

Download the movie these stills were taken from (800K DivX file)

I then moved the target out to 5ft and tried again. I got one hit before my crowbar triggered.

5ft arc- Pretty fly for a solid-state guy :)
Download the movie this still was taken from (800K DivX file)

Still alive and ready to kick more ass (huh huh cool)

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