RE: Ford Coil Triggered Gap Testing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Gary,

I put a 25 ohm power resistor across the dimmer output and now the phase
varies nice and smoothly through 5mS (~110 degrees).  The resistor makes
the control far more stable.  It also burns off some heat now but the
science still continues ;-)  The resistor runs the dimmer back in it's
normal mode and cleans things up significantly.  The Ford coil is just in
parallel with the resistor so the dimmer load is very resistive.

The spark output now tracks roughly in proportion with the AC Line voltage
at the firing point but still seems like it is easily enough to fire a gap.

I would give more detail on the circuit but I change it every time I look
at it :-))

Cheers,

	Terry


>Hi Gary,  
>
>The amplitude varies a bit but nothing really significant.  The "power" of 
>the arc seems to change some but not really sure that is of any use.  The 
>phase timing only varies about 10 degrees on mine but it can be adjusted to 
>the top of the AC line signal and a little before.  There is significant 
>jitter at least while it is arcing.  So the phase adjustment part needs work 
>still.
>
>Cheers,
>
>	Terry
>
>At 09:49 AM 8/1/2001 -0400, you wrote:
>>Hi Terry:
>>
>>What is the consequence of adjusting the dimmer control with this circuit?
>>Does the amplitude of the HV pulse change, or does just the phase/timing of
>>the HV pulses change, or do both timing AND amplitude change?  And for
>>timing, what is the range of adjustment relative to mains zero-crossing?
>>
>>Thanks, Gary Lau
>>MA, USA
>>
>>>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>>>
>>>Hi Marc,
>>>
>>>I fiddled with it a bit and now the AC line input looks like:
>>>
>>>http://hot-streamer-dot-com/temp/CoilTest/NewACinput.gif
>>>
>>>And the coil input looks like:
>>>
>>>http://hot-streamer-dot-com/temp/CoilTest/NewCoilinput.gif
>>>
>>>Some of the voltage spikes are radiated noise getting on the big probe and
>>>are not real.  There is a 240 volt MOV across it and if I disconnect and
>>>short the probe, the noise is still there ;-)  The Tek5100 probe would be
>>>far better but the big probe can take a direct 40kV hit.
>>>
>>>So it is well under control and very tame now.  I'll have to look at the
>>>grounding system some more and see if I can get rid of that $30 line
>>>filter.  It would be nice to model the thing and do some fault studies
>>>(like discharging the primary cap into the coil's output and the coil's
>>>input wires) to be sure there are no holes that could blow it up.  Far from
>>>done yet but the problems should be tiny now...  Probably should ground the
>>>coil can too...
>>>
>>>Cheers,
>>>
>>>	Terry
>>