Re: Ignition Coil Power Supply QUestions (fwd)

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Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 20 May 2007 22:36:09 +0100
From: James Howells <james@xxxxxxxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Ignition Coil Power Supply QUestions (fwd)

I have had several ignition coils running now and the best solution I have 
found is to drive them with a NE555 oscillator  inputting into a mosfet
The primary IG  coil can have a supply from 10 v to 24 volts - battery or 
mains PSU
http://www.rmcybernetics.com/projects/DIY_Devices/homemade_ignition_coil_driver.htm
A very good driver is the PWM on the rbcybernetics site
http://www.rmcybernetics.com/projects/DIY_Devices/homemade_pulse_controller.htm

USE TWO power handling device ( 2 x 2n3055 or what ever you decide to use ) 
and lots of cooling VERY big heat sink or salvaged CPU fans


Then rectify the output of the  IG coil with 30Kv diodes or higher

Then place the primary capacity bank across the circuit and the spark gap 
following in series  ( the opposite to what you would normally do)



A small coil will most likely need 3 - 4.5 nF capacity BUT HERE IS THE BUG 
BEAR

it needs to be 40Kv rating .............. this is the only  stumbling block 
I find

I have just blown 30 usd woth of Chinese caps - 30 at  2 kv

I have run at 20Kv total rating with ceramic caps and thought I would  "get 
away" with
 26Kv with polypropylene cap ..... I did not !

Getting High Voltage capacitors for ignition coils and flybacks IS my single 
biggest problem in the UK


Digikey do them but want to charge me £21 ( 42USD ) to send me 20 USD
 worth of caps
Well! that's my practical input





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----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, May 20, 2007 8:24 PM
Subject: Ignition Coil Power Supply QUestions (fwd)


> Original poster: List moderator <mod1@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 20 May 2007 14:13:00 -0400
> From: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: Ignition Coil Power Supply QUestions
>
> Hello,
>
> My ARSG project has been temporarily (for a few days) interrupted so I can 
> make a small coil for someone as a gift, because they have supplied many 
> of the parts necessary for my larger coil (old microwaves, piping, fans, 
> etc.).  I've wound a small secondary and filter chokes, but am trying to 
> figure out a good power supply for it that would be small and low power. 
> I think the cheapest way of doing this would probably be to use a few 
> ignition coils.  (If there's a better way for about the same price and 
> power level, suggestions are welcome.)  Anyway, I had a few questions 
> about ignition coil power supplies relating to Tesla coils.
> The first type of ignition coil power supply that I thought of would be to 
> use one or two ignition coils as normal autotransformers.  With 
> approximately a 1:100 turn ratio, 120V on the primary could yield a very 
> reasonable 12kV on the secondary in a nice sine wave.  They would have to 
> be ballasted, of course, probably capacitatively on the primary, like the 
> common mains ignition coil driver.  The problem I see is that I think most 
> of the voltage would be dropped at the ballast.  From searching the 
> internet, it seems to me that the unloaded inductance of the primary of a 
> typical ignition coil is around 3mH, yielding around 1.1 Ohms of reactance 
> at 60Hz.  A reasonable capacitative ballast would be a 10uF motor run 
> capacitor (which I happen to have on hand), which would yield about 165 
> Ohms of reactance.  This means that the majority of the voltage would be 
> dropped by the ballast representing a corresponding decrease in the high 
> voltage produced, right?  And is there any good way to get around this?
> The second type I considered was the typical ignition coil mains power 
> supply, consisting of a capacitor, triac lamp dimmer, and ignition coil 
> primary in series.  I know that some people have used these to power Tesla 
> coils, but wouldn't the high voltage waveform be far from ideal for Tesla 
> coil use?  Examining the waveform, the first part of a cycle on the 
> primary (before the triac kicks in) would be a normal sine wave rise, but 
> during this portion, wouldn't the high voltage produced be severely 
> limited by the series capacitor?  Then, when the triac cuts in and gives 
> the inductive kick, a much higher voltage is produced, but since the gap 
> fires at that point, it doesn't go into charging the capacitor.  Is this 
> correct?  And am I correct in thinking that it would be a problem?  Also, 
> the second inductive kick on the first half cycle of the 60Hz primary 
> waveform would pretty much go to waste, as well as the part of the cycle 
> after that before the waveform crosses 0, right?  And if these are really 
> problems, is there a good way to fix them?
> Is there any better way to drive ignition coils than these two for Tesla 
> coil use?
>
> Thanks a lot,
> Chris
>
>
>
>
>