[Prev][Next][Index][Thread]

Terry's GM HEI Coil Update.

Hi All,

	Tonight I tested my new and improved Tesla coil made out of a General
Motors High Energy Ignition coil.  This new coil uses a brand new HEI coil
and has much greater high voltage stand off capability.  Also the tuning is
improved and some instrumentation was applied to monitor its performance.
My notes on this testing are as follows:


	Unlike the previous test, I had the secondary grounded this time :-))  The
high voltage supply worked perfectly and the problems it was having were
solved.  In general the whole thing worked much better with the secondary
grounded.  I highly recommend this :-)  

	I monitored the primary cap voltage tonight.  I ran with 600, 800, and
1400 volts of charge across the 1.6uF primary cap.  This is more than I
originally intended but the sparks get bigger with more voltage so it must
be ok :-)  My cap will self protect itself at 1800 volts (MOV) so I have a
little left before I have to defeat the protection :-)  At 1400 volts I
noticed that I was standing pretty far back.  At 1.6 joule pulse power at
10kHz (I think it is over 180 kV!) the output would be pretty nasty to
touch.  I have touched it at much much lower levels and it definitely packs
a painful punch.  The final beginner's coil power will need to be much less
than this level!  The scope also showed that there can be substantial DC
offsets in the output.  At these extreme test levels, I must wonder if the
output is getting near the lethal area.  No good way to test this but the
danger is definitely getting serious in the testing I am doing.  This
special testing is definitely NOT for the beginner!!

	I had the scope and field probes up tonight.  At the touch of a button,
the printer would spit out the captured waveform.  I have definitely grown
used to this little luxury!  I have simple 1/2 inch diameter steel rods for
a spark gap.  However, the quench was always on the first notch!  The
voltage and current in this machine are certainly below our normal levels
but I was very surprised at the perfect quench.  The firing voltage varied
substantially so there is improvement to be made to get a more consistent
firing voltage.  I'll have some experimenting to do with this new gap
application!

	This was very interesting!  The output voltage waveform always has a very
high initial spike which is perfectly reproducible from bang to bang.  This
initial spike is 50% higher than the next larger spikes.  Since this is a
DC powered (charges the primary cap through a diode) coil, I can make this
initial spike positive or negative by reversing the primary leads.
Remembering our past posts about positive voltages like to arc more then
negative, I changed the polarity of the spike from negative to positive.
THE SPARK LENGTH INCREASED 50% WITH NO OTHER CHANGES!!!!  It was really
amazing!  All that ionization stuff is absolutely true.  Positive voltages
appear to be able to jump 50% further than negative voltages from this
test.  This is a very profound demonstration and the implications are far
reaching!

	I never went above 1BPS and I didn't connect it to my big neon transformer
tonight.  I think that was bad for my last coil :-)  After tonight's
testing, my coil is still working fine!  Output voltage was tested tonight
with great results.

	The GM HEI coil is immersed in oil.  It was very noticeable that whenever
the coil fired, the oil would violently "jerk".  This is due to the high
voltage charging the oil suddenly.  This is no problem for me (the epoxy
joints would fail from this eventually) but the designs of high voltage
capacitors should allow for considerable mechanical vibration I would
think.  I must wonder if this is why oiled filled caps like to leak after a
time.  More power probably would have started splashing oil out of the
tank.  I need to add $12 of mineral oil to the price list too.



BTW - Just in case anyone ran out and bought a coil and other stuff in
hopes of claiming my coveted GMHEICSLR (General Motors High Energy Ignition
Coil Spark Length Record) for themselves, the new record is 12.2 inches!!
I could have been longer, but with no real competion, I decided to save my
coil for another day.  Just remember, I may not be telling you
everything... ;-))


	Terry
	Holder of the coveted GMHEICSLR at 12.2 inches!