Re: Sam's High-Power Car Ignition Coil Driver <= Now running1.1kW...
to: Sam, Barry, Scott
Did you guys ever consider firing one of your systems into an old x-ray
xmfr coil? Most dental x-ray units hit 90 to 100 kV with two separate
coils running similar to a NST configuration. When the xmfr units die
usually one of the coils is good and most x-ray repair shops would part
with the dead xmfr for free. These are beefy units rated around 5-10 kva
for short duty cycles, 220 v input with 45-50 kV output per coil, and
already in oil. Your system might give you some awesome sparks with one of
these units modified slightly to fit your driver. Just a passing thought.
From: Tesla List <tesla-at-pupman-dot-com>
Subject: Sam's High-Power Car Ignition Coil Driver <= Now running1.1kW...
Date: Wednesday, January 06, 1999 5:04 PM
Original Poster: Sam Barros <sambarros-at-yahoo-dot-com>
>Date: Sun, 03 Jan 1999 12:33:11 -0700
>Subject: Re: Sam's High-Energy Double Car Ignition Coil Driver...
>From: Tesla List <tesla-at-pupman-dot-com>
>Original Poster: "B**2" <bensonbd-at-erols-dot-com>
Thanks a lot for writing, Barry!
>Hi Sam, All,
> I use a 0.33uF capacitor in series with a 10 Ohm non inductive
>power resistor. I put this in parallel with my SCR. I also put a
>stack of about 20 1n4007 in parallel, antiparallel to the SCR. The RC
>network eats the hf that would destroy the diode and SCR. The diodes
>protect the SCR from reverse voltage. They also provide energy
>savings by recharging the main capacitor with the charge left overs
>not eaten by the secondary. These values have been arrived at by many
Yeah, I got my value for the caps like that too… I still don’t get
why you need those diodes… I have a 600V 12A SCR and it handles the
pulses just fine. Never had to replace one except when I short
something out accidentally (or on purpose:-)…
> My SCR pulser uses an scr with no writing on it from the ham fest.
Mine is a TIC126-M for 600V 12A, trigger current 20mA.
>I bought 2 SCR's and used the second one to find the voltage breakdown
>limit. I tried several different diodes across the SCR to protect it
>from reverse voltages when the arc on the secondary of the ignition
>coil connects. The RC snubber network was calculated and tweaked from
>the General Electric SCR manual. My main capacitor is 10 uF. The
>power supply is 600 Volts at about 1 Ampere.
That’s 600W input… My system runs more power but you get longer arcs
because of the increased voltage… Soon I’ll have 600V on my primaries
too:-)… Just you wait, TERRY…
With dual cored ignition
>coils at about a few hundred Hz it gives a 6 inch arc in air.
I am VERY impressed!!! In fact, I’m amazed! We need to discuss this
sometime soon… I would be very interested in having a look at any
schematics you might have (if you are kind enough to show them to me).
As I said before my driver is no way near finished and I need all the
help I can get to make it work. If you all help me, everyone profits…
I am spending my money and time on this driver and I’ll post it on the
list for all of you to build it as you wish just as soon as it’s
finished. Please have some consideration for that and help me out if
>is similar to that of a potential transformer.
Mine is pretty weird… It’s half way between a NST and a MOT… Kind of
thick and yellow… unfortunately its not too stable and it breaks out
into a series of sparks when you go beyond 8CM. At 10Cm it’s just a
few sparks… Powerful ones, mind you.
The noise is
My driver also makes a hell lot of noise when I run both coils in
The coils soften after about 15 minutes.
Ummm… What do you mean by the “soften”? What kind of coils are they?
The SCR is cold
>to the touch.
Despite the 12A rating my SCR needs a heatsink to remain at a
The 1n4007 diodes are also cool to the touch.
I only have one 1kV 3A on the input. It gets warm but no way near hot.
>snubber resistor is a bit toasty but not too bad.
Whatever I use gets as hot as it can be… The 1.1kW heater element I
have now could probably cook a meal in a couple of minutes if I left
> I have never discussed this circuit or my apparatus before because
>it is VERY DANGEROUS. The output is pulsed DC. Very Very Dangerous
>and extremely painful as well ,if you live.
Now I just HAVE to say something about this, Barry. You are
forgetting that this is a TESLA list. Dozens of us here have pole pigs
or pole pig sized transformers on our backyards. We cook hotdogs with
multi-kilowatt arcs, we explode water and wires with pulse capacitors,
we crush beer cans with 150Pound pulsed-discharge devices (at least
Bill does:-) and MANY of us work with very deadly devices as a Hobby.
We all know there is a danger involved in it and we are all ready and
willing to accept the risks. No electrical device is too dangerous
because, unlike explosives (just had to mention this because of my
“first-hand” experience:-), you don’t ever have to expose yourself to
the threat. You set it up, plan ahead, calculate the risks, stand well
back and only than plug it in. I work a lot with 2 MOTs in parallel
outputting over 3kW. That is more than any ignition coil can possibly
take (I decided they are not physically large enough to stand the
magnetic flux and heat I think the limit for a single coil is >1000W
before the core saturates and heat build up faster than it can
dissipate). It is more lethal than the driver you describe and I see
no big deal about it ( don’t think anybody here does). I don’t have
any plans of contacting the output and as long as it stays that way
I’ll be safe. I learned a lot from this list and I am still learning.
I appreciate each and every post on it because it contains what people
spend money and time researching on. I deeply admire many of its
members (the list of names is too long) and I feel I own everybody
here something. You guys share your expts with everyone else and I
think I should too. I will post anything I think might be of interest,
and, as you should do, I trust that the ones that try it are the ones
that know what they are doing (and I am sure many of us do) and the
ones that don’t know what they are doing either stay off it or decide
to try it at their own risk, at which point I am not taking any
responsibility for their results.
Sorry for the speech… Just had to say it…
Anyway, this is very, VERY impressive work you are doing, Barry, and
I really want to discuss some stuff with you. Right now I have my
driver running at 1.1kW, limited by an oven heating element. The SCR
runs HOT, the diode and coils get warm. It will go to 1.5kW, I think.
The thing troubling me (this question is open to anyone who thinks he
knows the answer) is that I have 4uF of capacitance in parallel with
the coils, and 16uF in parallel with the resistance. Any attempt to
increase or decrease any of this capacitances decreases the output. I
don’t know why but it does. I do know why your device arcs longer than
mine though: You’re using 600V on it. I plan to do that too, with a
voltage Doubler , but I want to get some minor problems solved first.
Well, anyway, at 1.1kW there is MORE than enough juice to charge up
more caps. So I don’t know why I have to stick to those puny 20uF
overall. Anybody can think of a reason why changing cap values
decreases the output voltage? I considered the system going out of
tune but it can’t be that…
Keep up the good work!
Sam Barros (now with a 1.1kW coil driver!)
"The Less You Know, The Better You Sleep"...
"Evolution Stops When Stupidity Is No Longer Fatal"
"If At First You Don't Suceed, Increase The Amperage"
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