Re: [EVDL] Zener regs: Can I get use 'em & still get a full charge?

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Discussion Starter · Nov 2, 2010

Re: [EVDL] Zener regs: Can I get use 'em & still get a full charge?

Robert,
A Zener is a diode installed backwards. so in the direction we use them
we are using the higher reverse voltage rating as the operating voltage, and
not the forward voltage drop of about 0.7 Volt.
Temperature stabilized Zeners include both reverse and forward biased
junctions inside the package as the voltage increases with temperature rise
in one way and decreases for the temperature rise at the other junction then
the overall Zener Voltage is the sum and as one drops the other rises
resulting in a very constant resulting voltage.
Regards
Dennis Miles
++++++++++++++++++++++++++++++++++++++++++++++++++++++

Lee Hart <[email protected]> wrote:

> Robert Johnston wrote:
> > don't Zener diodes have a 0.7v "drain" before they conduct? So a 6.8v
> > Zener wouldn't be conducting completely until 7.5v.
>
> No, they don't work like that. The spec sheet for a zener shows the
> voltage and current at a number of points. For the 1N5342B I use, the
> specs are:
>
> 6.8v +/-5% at 175ma
> 6.65v at 17.5ma
> 5.2v at 0.01ma
>
> The regs use two zeners, and a #43 lamp in series (plus a 10-ohm
> resistor across the lamp). These have a nonlinear resistance, so the
> resulting current vs. voltage looks like this:
>
> 13.5v at 1ma
> 13.75v at 10ma
> 14.0v at 100ma
> 14.2v at 200ma (lamp begins to glow)
> 15v at 500ma (lamp brightly lit)
>
> The 6v version uses the same parts, but has just one zener in series
> with the lamp, and two zener+lamp pairs in parallel. Thus it has about
> half the voltage, and double the current.
>
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
>
>
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