Re: (ET) E15 goes forward/forward

["tjwilhelm" <tjwilhelm stelle net>]

Just a thought on relay burn out...

Often times, a reverse-biased diode is installed in parallel with a
load-coil (like a relay coil) to help prevent contact burnout.  When a coil
is quickly shut off it immediately (and very briefly) emits a huge 
kick-back
voltage (ala cattle prods, stun guns, etc.).   This high voltage can cause
contact arcing and, hence, contact burn out.  The reverse biased diode
(known as a "freewheeling diode") shorts the kickback voltage back onto the
coil, eliminating arcing at the contacts.

If your relay does not have a built-in freewheeling diode, you may want to
add one.  Do a Google search and I'm sure you'll come up with a bunch of
info one this.

Hope this is useful,
Tim Wilhelm

----- Original Message -----
From: "paul gilbertson" <paul gilbertson net>
To: <elec-trak cosmos phy tufts edu>
Sent: Sunday, October 10, 2004 10:15 AM
Subject: (ET) E15 goes forward/forward


> I did the dreaded "threw the ET in reverse while moving forward" and
> burnt out the reverse relay.
>
> Now about 4 replacement relays from Keith later, I still can go only
> forward no matter where the control is.  The relay accurately fires but
> the ET just moves forward either way I move the speed control.  I have
> verified that the reverse relay works. Numerous relays that I have tried
> have had the same result. They all have worked in the speed relay
> position and I watch it trigger.
>
> So, now what should I check/do?
>
> Missing reverse in Minnesota.
>
> Paul
>
>
>
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