Re: Newbie Questions

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

Original poster: "Jonathan Peakall by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jpeakall-at-madlabs.info>

In flyback drivers I have had good luck with the HV3055 sold by All
Electronics. MUCH more durable than the regular 2N3055. Heavier case, higher
voltage rating. I haven't used them on an IC, but have yet to blow one on a
flyback. Unless I was doing something really silly ;-P

Jonathan

www.madlabs.info

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, April 25, 2003 6:39 AM
Subject: Re: Newbie Questions


 > Original poster: "Stephen Conner by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
 >
 > At 20:58 24/04/03 -0600, you wrote:
 > >Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > ><jtf-at-dejazzd-dot-com>
 > >
 > >Stephen Conner wrote:
 > >
 > > > The base bias resistor is probably too big even for 12 volts.
 > > > ...... That would mean using a 20 ohm resistor, ....So you ought to
put an
 > > > extra emitter follower in.
 > >
 > >Stephen....your reply helped a lot. Added an emitter follower, (still
used
 > >the 100 ohm
 > >base resistor) and the spark doubled in length to 1/2 inch. Changed the
 > >base bias
 > >resistor to 22 ohms and gained another 1/4 inch, for a total of 3/4 inch.
 > >The spark was
 > >screaming :-) Then it all stopped :-( Guess the NPN transistor smoked.
 > >Didn't have the
 > >time to measure current, before it fried.
 > >
 > >Need to buy more transistors. LOL
 >
 > Don't buy 2N3055s, they suck for this application. You're trying to
 > generate a hi-voltage spike by turning the transistor off suddenly, but
the
 > 2N3055 can't take more than about 70-100V before it dies. A specialized
 > high-voltage switching transistor like the BU208D ought to work much
 > better. Note: The BU208D is easy to get over here in Europe but might be
 > rare in the US. Maybe someone else could suggest an equivalent?
 >
 > You can find a couple more ignition coil drivers at
 > http://www.powerlabs-dot-org/ My favourite one runs straight off the 120V line
 > and uses a SCR instead of a transistor. It gives pretty impressive results
 > when driving 2 ignition coils, but could be a bit dangerous.
 >
 > Steve C.
 >
 >
 >
 >
 >
 >