Odd behaviour while cold....

prayami · Joined: 22 Dec 2004 Posts: 78

Hi...I am using 18F4525 and CCS PCH C Compiler, Version 3.249 .

We are using 10MhzX4(PLL) = 40MHz crystal.

Our product work fine all the time. Our product is working on the car so when it is too cold nearer to 0 degree then it seems behaving wrong.

I checked the temperature rating of processor and other component
but they are far greater than we require. We tried to put into the freeze
for a while and test again then it is doing the same.

Can anybody guide me, what can be possible reason for that?

What can be the precausion for that?

Here is, What is it doing while cold:

prayami · Joined: 22 Dec 2004 Posts: 78

Is there anybody, who came across this kind of cold problem.

Is there anybody who can guide, the possible remidy or precausion
while cold...!!

I am using #SEPARATE statement at 5 methods in my program but not
before any interrupt and at the beginning of the .lst file it is written like
this:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Get a can of "chill spray". It looks like this:
http://www.elexp.com/che_403a.htm
It comes with a little red plastic tube, which allows freezing a small
area precisely.

Freeze each component on the board, one at a time. Then you
can find out which component or chip is flaky when it's cold.

Right now, you assume it's the PIC, but it might be the crystal
that is flaky. With the can of chill spray, you can find out the
exact problem.

newguy · Joined: 24 Jun 2004 Posts: 1903

Another possibility is a bad solder joint/joints. Components themselves will rarely cause troubles, but a relatively small temperature swing is pretty much guaranteed to unearth bad solder.

Definitely heed PCM's advice and get a can of chill spray. It will help to isolate the problem chip and/or solder.

iso9001 · Joined: 02 Dec 2003 Posts: 262

Anyone know if there are chain or franchise stores in US that sell those ?

Walmart, target, ACE, Home Depot, Frys, etc ?

I know a can of compressed co2 used upside down works for a little while Very Happy

But it would probably be a good idea to have one of these for testing.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Fry's definitely. Look in the chemicals section.

dyeatman · Joined: 06 Sep 2003 Posts: 1923 Location: Norman, OK

Radio Shack carries component cooler as well....

Catalog #: 64-4321

prayami · Joined: 22 Dec 2004 Posts: 78

Thanks guys...

We tried component cooler. And it seems when we spray on processor
then it is doing funny thing. Because I tried to use internal RC oscillator
with PLL (32MHz) and it was doing the same thing while I was using
crystal.

But the processor is rated to work at -40C. Then it should not do that..

Is there any other possibility any body know..??

Thanks...

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Describe the crystal circuit. i.e., crystal, capacitors, resistor (if any).
Post the component values. If possible, give the manufacturer and
part numbers.

prayami · Joined: 22 Dec 2004 Posts: 78

Thanks...PCM....

I faced the same problem while using internal RC oscillator.

But still , Here are the component values:

Crystal is of 10Mhz and it is from Cmac and FS10.00P written on it
so it may be the part number.

Both the capacitor are of 18PF.

Sorry crystal circuit is not displaying properly.

But other end of both the capacitors are connected to ground.

Thanks...in advance....

Circuit:

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

If you can put a frequency counter on the oscillator output (osc2) and see if that shifts when things get cold. If so then you know that is the problem.
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