[dorkbotsea-blabber] EL wire and Zener diodes

Steve Greenfield alienrelics at yahoo.com
Mon Apr 25 18:19:24 EDT 2005

> > You -must- use current limiting resistors with the zener
> diodes. It
> > sounds like you are driving the EL wire right from your
> amplifier,
> > that is a low impedance output and the first time you go over
> the
> > zener voltage it'll burn out the zener.
> >
> It's actually coming off a step-up transformer which has an
> impedance 
> of 300 ohms on the side where the zeners would go.  Would the 
> current-limiting resistors go in series with the zener diodes,
> then?

Should go: transformer lead 1, resistor, zener pointing up, zener
pointing down, transformer lead 2. Connect the EL panel across the
two zener diodes.

As you had them in parallel, it'd clip at .7V peak as both zeners
would forward conduct.

To overly simplify things tremendously: 300ohms, 200V max and 100v
zener diodes. 100V/300ohms = 0.3A. 100V x 0.3A = 30W, but each
Zener takes a half cycle so call it 15W. Are your Zener diodes
rated at 15W?

However: transformer impedance is not a simple thing. If you start
clipping it, funny things can happen. So the real power dumped into
the zeners may be higher or lower than that.

Seems like it'd be simpler and surer to do all your limiting on the
low voltage side.

Steve Greenfield               // Digital photography, scanning,
Polymorph Digital Photography // retouching, and photomorphing
253-318-2473 voice           // to your specs.
polymorph at polyphoto.com     // 
http://www.polyphoto.com/  // Based in Tacoma, WA, USA

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