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Re: [TCML] Calibrating a sync spark gap
Here's some pics:
Scope showing the AC line, the trigger point is at the very left edge
of the screen. The upper trace is the current probe but the pulse is
too short to see at this timebase. In the second pic you can kinda
see that it's triggering on both peaks.
http://www.thorbass.com/images/Tesla/ssg/ssgScope1.jpg
http://www.thorbass.com/images/Tesla/ssg/ssgScope2.jpg
This is a shot of the bolt with the titanium rod through it. You can
just make out the set screw on the left side at the bottom of the bolt head.
http://www.thorbass.com/images/Tesla/ssg/ssg3.jpg
Test setup...
http://www.thorbass.com/images/Tesla/ssg/ssg2.jpg
At 01:38 PM 1/25/2009, you wrote:
I'm in the process of building a synchronous spark gap. I have
modified a motor and built a rotor from G10. My electrodes are
mounted by drilling a hole the long way through a bolt, then
drilling a hole sideways into the head and tapping for a set
screw. The bolts are mounted through the G10 with some washers as
cooling fins, and titanium rods stuck through held in place with the
set screws. I'll upload some pictures later and link to them.
The problem is how to set the position correctly. Here's what I did:
Hook up an NST to the gap and connect one channel of my scope to the
AC line of the NST (actually going through a variac too). I took a
piece of hookup wire, alligator clips on the ends, and wrapped it
around one of the output wires of the NST, about 5 wraps. The ends
of this wire go across the other channel of the scope, signal to
gnd. Basically I built a cheap current probe.
Now firing the thing up, I set the scope to trigger on the current
probe. Basically getting a pulse every time the gap lines up. And
looked at the position of the AC line voltage relative to the pulse.
Using this method I got a fairly consistent display on the scope and
was able to adjust the position by rotating the motor in the mount.
Question, I think I remember reading that I should sync to about 85%
of peak. In other words it should fire a little early, is that right?
- Karl
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