Re: ignition coil Plasma ball

to: Jim, Phillip

Commercial globes such as we manufacture use a flyback type running with an
adjustable freq for tuning to the gas mixture.  The tuning range is usually
only 1 kHZ wide for best display.  We never use style transistor circuits
with flybacks, but, due to reliability issues, always use SCR type driver
systems for ignition coil driver circuits which we use to trigger our large
Marx impulse generators.

Globe gases are typically neon, xenon, and krypton (at $13,000.00 per
liter -- no misprint) blended in a gas manifold.



-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Saturday, July 17, 1999 3:31 AM
Subject: Re: ignition coil Plasma ball

>Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>Pulse width is THE critical parameter when driving an ignition coil with a
>low voltage (i.e. 12V).. You have to leave the power on long enough to get
>the current through the coil high enough (that I = V/L *delta T thing) so
>that you have a reasonable amount of stored energy (L*I^2/2).. A typical
>coil current is 5A...
>You can see that doubling the time makes the energy 4 times greater, so it
>has a very large effect.  The HV impulse comes when the transistor turns
>off (BTW, a 3055 won't last too long with 400 V across it... every time you
>run it it gets a bit more thrashed... or, it just avalanches and acts like
>a 100V zener, and dissipates a fair amount of energy and, more important
>limits the output voltage) (Use an ignition transistor like a 2n6062 (I
>think that's the number) with a BVceo of 400V, or a horizontal output
>transistor (A radio shack part) with a BVceo of 700V)... both of these are
>TO-3 packages, BTW).
>In a V8 car application,  running at 6000 RPM (100 RPS), the pulse width is
>about a millisecond.  (PRI = 2.5 mSec)
>Capacitive discharge ignitions don't rely on the slow ramp up of current
>and then the Ldi/dt to get voltage.. They charge up a (typically 1 uF) cap
>to around 400V and just dump it into the coil.  400V doesn't take as long
>to get the coil current up to 5A.
>> From: Tesla List <tesla-at-pupman-dot-com>
>> To: tesla-at-pupman-dot-com
>> Subject: ignition coil Plasma ball
>> Date: Thursday, July 15, 1999 6:11 AM
>> Original Poster: Philip <shadow42-at-totcon-dot-com>
>> Before I have tried many times to get a ignition coil based plasma ball
>> to perform. I do beleive ive found what I was doin wrong and will pass
>> it along. I am now useing a pulse generator to do my work instead of the
>> 555 of the past. Here are my system specs.
>> Coil - Ford standard coil 12v
>> Pulse gen - Systron donner 100a
>>    settings
>>                Repetition rate - 1mhz
>>                Pulse delay - 10us
>>               Pulse width - 1ms
>>               Base voltage - 3v
>> Power source - 12v sealed gel cell battery
>> Transistor - 2n3055
>> Heatsink - 12x5" all finned stock
>> Globe used - 5" commercial globe (gas content unknown)
>> I found that adjusting the pulse width was more critical in the
>> performance than the repetition rate. Amplitude setting was set about
>> 3v. 3055 never became warm during operation. I have a digital cammera
>> but it will not photograph the plasma ball well. I tried and tried. I
>> even fittled with exposeure time to no avail. I need to get out the real
>> cammera. Hope this helps someone. My original photos are at
>> http://hv.hypermart-dot-net/pb.html.
>>    Philip Mac Duffie