12 Oct
2000
12 Oct
'00
4:54 a.m.
Tarsi wrote:
The worst problem about running power directly from
the car's supply is
that it's not a clean, steady stream of juice. Computers run best on clean
power, and a car's power is anything but. Hence, the deal of being grossly
inefficient in changing 12V-->120V-->12/5V is true, but if you're using an
inverter + UPS or some such, you get the benefit of the cleaning up of that
power supply.
That's an understatement; voltage can fluctuate
between 8 and 15V as different subsystems in the car
are turned on; then there are spikes in excess of 100V
induced by different systems; and then, if your battery
contacts are less than perfect you can have 30VAC, rectified
(or not, if the rectifiers fail in a particularly nasty
mode!) from the alternator.
I have some experience using electronics in cars, having
worked in control systems for engines, as well as active suspension
systems and active four-wheel steering, not to mention my HEV
experience. Working with a 20KW, 380VAC alternator in a vehicle
is interesting. And it is weird when you see
that the throttle that you're adjusting by hand is linearly
related to the ~400VAC readings from the alternator :-) .
--
Carlos Murillo-Sanchez email: cem14(a)cornell.edu
428 Phillips Hall, Electrical Engineering Department
Cornell University, Ithaca, NY 14853