From: firstname.lastname@example.org (Bob Wilson)
Subject: Re: Automotive electronics
Date: Sat, 12 Oct 2002 05:08:00 -0000
Organization: Your Organization
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In article <3DA6F933.7BA6A61@xympatico.ca>, email@example.com says...
>Bob Wilson wrote:
>> In article ,
>> >Dear all,
>> >I am looking for design tips for automotive controllers like seat
>> >controllers, body controllers and automotive electronics in general.
>> >How have digital inputs for switches to be designed? Waht kind of
>> >protection, reverse polarity, short circuit, open load and so on.
>> >How are power supplies to design?
>> >How are analog inputs to design?
>> >Any references, links and/or tips about this field?
>> The 10-year old (but still excellent) Daimler-Benz specs that I got when
>> was working for an associated company in Stuttgart, required (among other
>> things) that the load must withstand 1 Joule of energy discharged from
>> a +200V and also a -200V source, dumped onto the load once per second for
>> period of several hours. Somewhat brutal.
>> This is pretty simple to rig up, and is all you need to know to make your
>> electronics bulletproof.
>> Viel Spass!
>In Motorola's Application note AN843 - A Review of Transients and Their
>Means of Suppression, there is a discussion of automotive issues.
>The mother of all transients is the so called "load-dump transient"
>which can produce upwards of 10 Joules @ 125 Volts peak in a single
>shot. Is it necessary to allow for this or is it already suppressed at
>the alternator? Motorola (On Semi) makes a gigantic suppression diode,
>the MR2535, which is intended for precisely this application. One would
>expect one to be installed in every vehicle at the factory. Is it so?
Nothing is suppressed at the alternator, or not on any alternator/regulator
that I have ever had apart. All that is in the alternator is the 6
rectifiers (2 per phase), plus another 3 small ones (one per phase) on many
Bosch alternators to supply the field, and a really cheap and crude
electronic regulator (a couple of transistors, a zeners and a few other
Of course this doesn't stop them from charging >$100 for a replacement
regulator (just like the >$800 for my car's engine management "computer"
that uses an old 80C39 controller, and about $25 worth of parts).