From: Mike Monett
X-Mailer: Mozilla 2.02 (Win16; I)
Subject: Re: zero-power toggle circuit; was, how to master electronics
References: <3DC517EB.firstname.lastname@example.org> <3DC57B4E.email@example.com> <firstname.lastname@example.org> <email@example.com> <3DD39D90.firstname.lastname@example.org>
Date: Thu, 14 Nov 2002 22:38:54 -0800
NNTP-Posting-Date: Thu, 14 Nov 2002 22:38:56 EST
Organization: Bell Sympatico
Winfield Hill wrote:
> High-side switching is dangerous, unless an effective form of
> short-circuit protection is provided, e.g. shutoff, foldback
> current limit, a quick fuse, etc. Low-side switching is used
> in cars, etc., because it has the nice property that a wiring
> short simply turns on the switched device. Recommended.
> - Win
A philosophical question. Cars have fuses or circuit breakers for each
branch. If there's a malfunction, wouldn't you rather blow the fuse? This
would disconnect the faulty circuit and prevent further mishap.
An inadvertent short that activates some function unexpectedly may cause
driver confusion at the wrong time, and could result in an accident.
I fondly remember one evening during final approach into San Jose when
the panel on my Malibu went crazy. We were on a checkout flight and the
owner of the flight service company that did the panel was with me in the
He told me to turn off the master switch. With only seconds to touchdown,
I thought this was the stupidest thing we could do, but I followed his
recommendation after telling the control tower we would be off the air
Recycling power fixed the problem, and we touched down seconds later. It
was a short somewhere in the relay system that controlled the panel.
I have full confidence in the person and the quality of workmanship he
produces. But if I was by myself on an approach to minimums and lost the
panel, I would be in deep trouble.
If there's a problem, blow a fuse and let me fly partial panel!