Problem with temperature

[Kmouly]

Hi all, I have a PI(Minediver2). when I test it in a cold site(about 0'C), its works too slowly and gives me false signal from time to time.
I don't why that occurs... the PI has a 16MHz crystal... in clod sites it works as if its crystal is 4MHz.

Do you know where the problem is?


-Kmouly

[Max]

the magic switch

Hi all, I have a PI(Minediver2). when I test it in a cold site(about 0'C), its works too slowly and gives me false signal from time to time.
I don't why that occurs... the PI has a 16MHz crystal... in clod sites it works as if its crystal is 4MHz.

Do you know where the problem is?


-Kmouly

Hi,
the "speed" you're talking about is probably the response/recovery time of MD. That time interval depends strictly on analog components in the signal path, expecially at integrator stage.

So I guess your xtal frequency doesn't change much with temperrature... and it's not your source of problems.

Be sure, instead, that cold temperature could modify the dielectric contants of many mediums so the cap(s) value(s) respect to nominal 20°C value(s) of noticeable amount.

Solutions ? There are. The easiest...

If you do not want that behaviour happens just modify your MD, put a switch and new cap(s) (where required, so again check your integrator path in schematic) in a way to get you a choice control between normal and cold temperature... : normal will use existing cap(s), cold will be related to new cap(s) you'll choose to match required capacity BUT at 0°C.

Use of quality caps will also partially solve the issue (some quality caps drift very few by temperature, but keep in mind that you need very hi-quality parts to match along extreme temperature change)

it's much like you'll do changing your jacket according to forecast!

PS: compications could be related to other issues, example... your critical component could be a cap that fix monostable time used to fix the sample time of a gate and thus propagates the effect to whole behaviour... in that case, like in the above you'll must first discover which component (as before check caps variations that are the most common cause) is involved and use countermeasures appropriated like I wrote above.

Kind regards,
Max