temperature range -- automotive

Question about power
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YahooArchive
Posts: 1463
Joined: Fri Oct 19, 2012 5:11 am

temperature range -- automotive

Post by YahooArchive » Thu Oct 25, 2012 6:11 pm

>Is it tough enough to withstand this environment? Would
> there have to be any special considerations in regards to mounting
> (vibration suppressing) or cooling?

The ARMexpress is rated -40 to 85C so temperature should not be a
problem. While 12V is allowed as an input power, that would be a lot
of power for the regulators to throw away, so some pre-regulation
would be best.

Vibration would be fine for the ARMexpress, but the concern would be
if a socket is used. Some way to hold the ARMexpress in the socket
would be needed, or it could be soldered directly into the motherboard.



YahooArchive
Posts: 1463
Joined: Fri Oct 19, 2012 5:11 am

Re: temperature range -- automotive

Post by YahooArchive » Thu Oct 25, 2012 6:11 pm

>
> Would
> there have to be any special considerations in regards to mounting
> (vibration suppressing) or cooling?


Unless you're building a Baja racer, you don't need to worry too much
about shock. Vibration _might_ be a problem with loosening socketed
components over time if you have a really solid mechanical connection
to the chassis. Anything that loosens that coupling helps: I used to
do a lot of work for a company that made the elctronics for propane
vehicle conversions. The controller modules were typically mounted
either to a plastic kick panel or carpeted area of the floor or
firewall. The boards were mounted to an aluminum case that kept them
from flexing and cracking.


Despite being used extensively in trucks and other vehicles with stiff
suspensions, they had a near-zero field failure rate.


Two things you want to watch out for are moisture and power.


If you haven't lived in an area with lots of snow, you may not
appreciate how easy it is to get lots of moisture in unexpected areas
of a vehicle's interior.


The power supply in a car is extremely nasty. The voltage varies all
over the map, from as little as 6V during cranking (maybe even less
if the battery is especially low) to over 16V when the engine is
running and charging the battery. Plus the motors, solenoids, and
other electromechanical doo-dads can generate lots of noise and ugly
spikes.


You need to make sure your power supply includes a series diode, and
something like an MOV or Zener to absorb the spikes.


And make sure your system can tolerate short-term drop-outs during
situations like cranking the engine.


HTH,


Ran

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