Re: flyback transformer HV question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>



 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Wednesday, August 06, 2003 6:53 PM
 > Subject: flyback transformer HV question
 >
 >
 >  > Original poster: "Ryan Molecke by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <ryan-at-molecke-dot-com>
 >  >
 >  > Hi all,
 >  >
 >  >     I've been playing with some flyback transformers, and have
succeeded
 > in
 >  > producing 1-2cm sparks from the HV output (the wire that had the
suction
 > cup
 >  > on it). I can't seem to find the HV return wire on any of my
transformers

Ground return pin is also found by trial and error
the pin which draws fiercest spark from the sucker-cap will be the ground
pin.

 >  > (I'll build my own soon enough), but I can generate sparks to a
grounded
 >  > wire.
 >  >
 >  > I'm using a simple, single transistor driving circuit on the
transformer.
 >  > I'm trying to use this as a driver for a plasma globe. This HV lead
does
 > not
 >  > seem to turn lightbulbs into plasma globes. I'm just putting the HV
lead
 >  > onto the baseplate of the bulb (I've also tried tying the bulb "return"
to
 >  > ground). I've tried various type of bulbs. A 40W clear bulb was
allowing
 >  > arcs through the glass to a grounded wire, but no streamers inside.
 >  >
 >  > Does this indicate that my transformer has internal diode(s)?

Yes -as does the the sucker cap which is the positive connection to the
final anode of the CRT in television or monitor use.
You almost certainly have an example of the more modern "diode-split" line
output transformer (LOPT) type of flyback where the AC is rectified
internally to provide the necessary DC for the picture tube; the older type
that produced AC to be rectified by a tripler is very obsolescent and
practically extinct.

  Am I hooking
 >  > up the bulb right? Anyone know?

You are probably connecting the bulb up correctly the trouble is, because
the output is DC not AC the type of flyback you are using is  practically
useless for driving a plasma globe or anything else that relies on a
capacitive current through the glass to provide the return path.

You could possibly use the high voltage DC power a very small spark-gap TC
and use that to power the plasma globe, but the primary cap would have to be
very small (i.e. measured in picofarads) as the current from the transformer
is most a few milliamps and a larger capacitor would take too long to charge
up between sparking.

Jolyon
 >  >
 >  >
 >
 >
 >