# [TCML] Frequencies

Bob Arenella rja12 at comcast.net
Mon Oct 12 10:05:46 MDT 2009

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 at bellsouth.net>
To: "Tesla Coil Mailing List" <tesla at pupman.com>
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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