[NLRS] Goof Proof Transverters

[Dr. Gerald N. Johnson]

Probably the shunt diode should be rated at least ten times the fuse
current because of the inherent time delay in melting the fuse is much
longer than the thermal time constant of the diode. I have observed that
the fastest (pure silver element) semiconductor "protection" fuses are
reliable indicators of semiconductor failure.

On 8/14/2010 10:01 PM, Marciniak, Ed wrote:
>
>
> You can go one better than that and use a transient absorber
> (basically a zener diode with a breakdown voltage above what may be
> supplied to the equipment normal) with a fuse. The transorb when
> subjected to a reverse supply becomes a forward biased diode..... For
> 50 cents or so, you get overvoltage and reverse polarity protection.
> The upside: no voltage drop, and overvoltage protect. The
> downside....replace a fuse, which with Murphy's law won't be
> convenienly available and possibly the diode itself if the fuse
> doesn't blow fast enough

And no energy lost holding the relay closed.

73, Jerry, K0CQ