RE: [TCML] Building a pulse generator

["Dave Halliday" <dh@xxxxxxxxxxxxxx>]

Also, the 3055 was the 'go-to' power transistor about 30 years ago (about
the time the 555 came onto the scene (designed by Hans Camenzind --
interesting person but has a lot of basic facts wrong on Tesla))

http://www.historyofelectronics.com/

http://www.edn.com/blog/1700000170/post/1930037993.html

There are choices that are a lot lot better these days. 

The pots will control the frequency, not the voltage. You are feeding it 12
volts. This is what you have in a car so the ignition coil is not going to
generate any more volts than what it would in a car.

Also, something to consider is that you are going to get AC out of the coil.
You need DC. You are looking at storing it in a capacitor to use for a
high-speed flash.  You only need a couple K-volts. Rectifiers rated for 30K
are expensive.

It would be a lot simpler to use some kind of isolation transformer
(Microwave Oven transformer) with a couple of voltage doubling stages after
that. The MOT is 110 in and about 2KVAC out. Put an advertisement in your
local newspaper saying that you are looking for dead microwave ovens and
stand back... (grin) You can then salvage a whole bunch of transformers,
high-voltage rectifiers and capacitors.

PLEASE NOTE that these caps will not be suitable for a high-speed strobe.
You need high voltage and low C

Dave

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx 
> [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Dr.Hankenstein
> Sent: Saturday, September 05, 2009 11:16 AM
> To: 'Tesla Coil Mailing List'
> Subject: RE: [TCML] Building a pulse generator
> 
> Speaking of mistakes, that is the worst schematic I have ever seen. I
> would expect the 2N3055 to pop after the first pulse! First of all, I
> would put a pre-driver transistor on the base of the 3055 to 
> lessen the
> burden on the 555. Next (and this is very important) the 3055 needs to
> be protected with a reversing diode from collector to emitter. The
> reverse pulse from the coil will very likely exceed the max voltage
> rating of the 3055 when the transistor turns off. There are 
> other things
> I don't like about this schematic. Too much to dwell over.
> 
> Good luck,
> Hank
> 
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Rhys Sage
> Sent: Friday, September 04, 2009 5:54 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Building a pulse generator
> 
> I build things slowly and talk about them a lot. Talk's 
> cheap; mistakes
> cost money.
> 
> I'm building the following circuit
> http://www.flickr.com/photos/sagephotoworld/3673918744/sizes/o/
> 
> It's going to be a pulse generator with the power supply taken from a
> 12v 4.16A 50W max LCD transformer. 
> 
> I have not yet made my mind up as to which ignition coil to use. I
> gather there are several varieties. I'll be after 25-30KV so 
> I'll go for
> a coil with a rating in that range.
> 
> Now my question - by varying the resistance of the two 10k 
> pots, will I
> be able to raise the output KW above what the coil normally supplies
> (20-25KV)?
> 
> Rhys Sage
> 
> 
> 
> SagePhotoWorld.com
> 
> 
> 
> America's favorite photographer.
> 
> 
>       
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