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Re: [TCML] Frequencies

Hi All,
Interesting reading, but lets look at some automotive basics: In a 4 stroke engine, the plug fires once / 720 degrees of crankshaft rotation, not 360 degrees of crank rotaqtion. Two revolutions= intake, compression, IGNITION and exhaust. Remember, the distributor (if so equipped) rotates at 1/2 the crankshaft speed. In a V8, every 90 degrees of crankshaft rotation= 1 power stroke. At 2 rpm, there are 8 firings of the ignition circuit. Modern cars use 2 different methods.....in V8 cars with coil packs, there are 4 ignition coils moulded into the coil pack. Each coil fires two cylinders at the same time, one at the top of the compression stroke (ignition) and another cylinder that is at the top of the exhaust stroke. Some vehicles have an individual coil for each plug. Chrysler calls this COP, coil over plug. 

Regards,
bob
----- Original Message ----- From: "Paul Brodie" <pbbrodie@xxxxxxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, October 12, 2009 9:14 AM
Subject: Re: [TCML] Frequencies
Excuse me. 4800 was a typo. Obviously 48000 is 6000 times 8 but 48000 divided by 60 seconds is still 800Hz. 
Paul
Think Positive
----- Original Message ----- From: Paul Brodie 
To: Tesla Coil Mailing List
Sent: Monday, October 12, 2009 01:12
Subject: Re: [TCML] Frequencies


You are right, Jim. I apologize profusely for my mistake. Mea culpa, mea
culpa, mea maxima culpa!
With the V8 it fires 8 times per revolution, which is why the experiments
show the arcs continuing to increase up to about 1000Hz. 8 times 6000 rpm
equals 4,800 discharges per minute or 800Hz. So, my point still stands. You 
do not drive ignition coils at anywhere near 10kHz or your output will
suffer dramatically.
Paul
Think Positive
----- Original Message ----- From: jimlux 
To: Tesla Coil Mailing List
Sent: Sunday, October 11, 2009 18:04
Subject: Re: [TCML] Frequencies


Paul Brodie wrote:
A standard commercial automobile engine runs at 6,000 rpm tops. The ignition coils are deigned to be driven at this frequency. This works out to 100Hz or less, 6000 divided by 60 seconds. 

Only if you have a 2 cylinder engine(!).. a six will fire 3 times per
revolution (300Hz) an eight more.. Got that V12 Jag and you will be
firing at 600 Hz.


From much
experimentation, I have found that the coils I have worked with, primarily the Accel Super Coil, will continue to produce higher voltage up to around 1kHz and then start to drop off. If you try to overdrive the ignirion coil, you will get less output, not more. Also, wouldn't it be better if you let everyone know what it is you are trying to accomplish with this? I believe you said you want to try to charge caps to first 25kV and then to 50kV in stages and use these to drive some sort of flash. Is this correct? 

This is the kind of circuit that is hard to do empirically.  You can
copy a known good circuit from someone else (e.g. the multitude of triac
dimmer, capacitor, ignition coil circuits) and it will work ok.  But if
you start to modify, or try to do other things, you need to understand
the theory to know where you're going.

ignition coils are not a great way to make a generic HV source.  They're
great if you want sparks or HV pulses (where the pulses are of a certain
shape and duration).  But as soon as you move away from what they do
best (e.g. firing a spark plug), you'll find you're adding circuit on
circuit to get where you need to go.

What, exactly, do you need, HV pulse wise?

Voltage, rep rate, load current, pulse width?
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