Re: Ambient temperature control

On 01/07/2024 04:16, Bill Sloman wrote:

On 1/07/2024 11:14 am, Don Y wrote:

Assuming you can keep a device in its "normal operating (temperature)
range", how advantageous is it (think MTBF) to drive that ambient
down?  And, is there a sweet spot (as there is a cost to lowering the
temperature)?

 It's generally figured that decay and degeneration proceed more slowly at lower temperatures. A popular rule of thumb is that a 10C temperature drop halves the rate.
 The Arrhenius equation says it depends on the activation energy of the process, and the factor of two in 10C would reflect an
activation energy of 52,900 J/mol (52.9 kJ/mol) which is pretty ordinary.
 

Also, is there any advantage to minimizing the hysteresis between
the ACTUAL operating temperature extremes in such a control strategy
(given that lower hysteresis usually comes at an increased cost)?

 Only primitive (bang-bang) control schemes have hysteresis. Learn about proportional-integral-derivative control (and it's more advanced variations).

This study suggests that for disc drives there is no advantage in
cooling them below around 40 or 50 deg C.
https://static.googleusercontent.com/media/research.google.com/en//archive/disk_failures.pdf
However, other product types may behave differently.  Some
encapsulated power supplies have an electrolytic capacitor
at the output which is very close to the output rectifier
diodes.  This capacitor will dominate the reliability of the
system and keeping it at a reasonably low temperature will
definitely have benefits.
Large temperature swings may cause fretting of connector
contacts if there is relative movement on each temperature
cycle.
John
John