[Rover] Stupid electronics questions

Thu, 16 May 2002 12:49:20 -0400

Hi Guys,
Just thought I'd share a little known secret about
relay coil transient protection.  To be even safer from
the horrors of the inductive "kick" voltage caused by
relay coils, you should also include a forward biased diode
in series with the positive supply-feeding the relay.
When the transient occurs, it "rings" with both positive
and negetive voltage excursions.  (sometimes very large
transients...I once lost a 3A voltage regulator from this
problem!).   The shunt diode across
the coil will suppress the negative transients, and the series
diode will help keep the positive transients from getting
back into your power supply, which is usually connected
to expensive equipment (!).  2 diodes are better than 1.
There is actually a Mil-spec on relays that addresses this
additional protection scheme...don't recall which one.
I would recommend the 1N4001 diodes over the wimpy
1N4148 types.

Keep your diode transients to themselves!
GL es 73,
Bill W3IY/R

http://members/fcc/net

----- Original Message -----
From: "Jacob Tennant" <[email protected]>
To: <[email protected]>; <[email protected]>;
<[email protected]>
Sent: Thursday, May 16, 2002 11:35 AM
Subject: [Rover] Stupid electronics questions

> 1. On a diode (1N4148) the little black line goes closest to the negative
or
> the positive?
>
> 2. On a 12volt reed relay, the power & ground goes to the coil contacts?
>
> Sorry for the stupid questions but don't want to screw this up!!!
>
> Jacob Tennant - K8JWT
>
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