Designing a PWM DC motor controller for under a car hood...

1) temperatures under the hood vary quite a bit, depending on location and operating condition. Worst case is obviously anywhere near exhaust components and away from airflow, and worst case for electronics is usually when starting up after a hot shutdown of the engine. Temperatures continue to rise for a while after shutting off the engine, since there may be no airflow or coolant flow. 2) Commercial temp range ICs may not be much different than industrial or military these days, except with respect to how much testing they've undergone before shipment. Lots of products use commercial temp range ICs at extended temp ranges. (Oh, horror!) 3) Regardless of which type circuitry you choose, your main challenges are likely to be in packaging the electronics for shock, vibration, temperature changes, ESD, EMI. Find out about auto electronics operating conditions like 'load dump transients'. 4) Brush-type motors generate lots of conducted EMI. Learn about bypassing and otherwise filtering this. Paul Mathews

[snip]

Called "soak"

When I was designing car parts I used a spec of -40°C to +140°C

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

The last winter I lived in Montana, the coldest day was -51F. But that was in the late 60's and the only electronics in the car was an AM/FM radio.

I wonder how the hybrid autos do in those temps.?

When the temp. got below -30F, it was impossible to start the car when it had cold soaked. So I kept a spare battery in the kitchen and took it out with me to jump start the car every morning. Yes, I even had a Corvair to avoid the anti-freeze problem. Ah, the good old days!

Al

Probably about as good as diesels. ;-)

=20

I remember visiting my brother in Minneapolis 30+ years ago. He=20 had a beetle, but had to take the battery in at night or it would=20 freeze (it was weak). His Dodge sat in the garage plugged into a=20 tank heater.

We've hit -30F a couple of times and -20F almost every year (though=20 not anywhere close this winter). Below about -20F my cars have=20 about a 50/50 chance of starting. One would either start instantly=20 or flood just as fast; flip a coin. It *rarely* (three days in=20 since records have been kept) gets above 100F so batteries last=20 longer than one would expect. Longer than they do in say, Arizona.=20 ;-)

--=20 Keith

Why dual? It seems to me that you don't really care about the frequency only the duty cycle matters.

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