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Propeller_Head
02-04-2007, 01:32 AM
What is the Operational Temperature Range of Propeller Chips? (Commercial, Industrial, Military?)

I am considering using one for Weather Measurements and it may get as cold as -60* F or so.

Thanks!

Paul Baker
02-04-2007, 01:02 PM
We are planning on testing for the automotive range which is -40 to 125C. However the part will not be tested in these ranges until the full datasheet (I am presently working on the preliminary), this does not mean the Propeller absolutely wont run at -60, frequently all it means is you'll have to derate the Propeller to make sure it operates as you expect it to. It has been our experience that it's not the microcontroller that is the weak point of a cold-weather system but one of the supporting components will fail first. Because of this it is important to test the final product in an environmental chamber. A couple of our customers make weather measurement systems that experience extreme temperatures (Peter van der Zee and Tracy Allen) you can ask them for pointers on what are the typical weak points in extreme weather systems.

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

Tracy Allen
02-06-2007, 11:30 AM
I took a Prop demo board down to -65 degrees Celsius in the chamber, while having it switch from 32 khz to 80 mhz operation, and also manually took it up and down through the brownout voltage. I've been talking with Paul about doing further temperature tests, when we both have time and when he has the more pressing specs are out of the way. I have a rather old CO2 chamber, but the factory controller is overridden by my own OWL2pe/Stamp controller/logger .


That one sample had no problem whatsoever with the transitions. The brownout detector and the oscillator and clock chain are analog blocks and are the most likely to have problems at temperature extremes. Chip assured us at the beta testers' meeting that considerable care was taken in the design of those circuits and left plenty of margin calculated for extremes of temperature. That is in line with what he just said in the manifesto about "why it works..."

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Tracy Allen
www.emesystems.com (http://www.emesystems.com)

cgracey
02-06-2007, 11:54 AM
Tracy,

Thanks for doing that test. Is -65 the limit of your chamber?


Tracy Allen said...
I took a Prop demo board down to -65 degrees Celsius in the chamber, while having it switch from 32 khz to 80 mhz operation, and also manually took it up and down through the brownout voltage. I've been talking with Paul about doing further temperature tests, when we both have time and when he has the more pressing specs are out of the way. I have a rather old CO2 chamber, but the factory controller is overridden by my own OWL2pe/Stamp controller/logger .


That one sample had no problem whatsoever with the transitions. The brownout detector and the oscillator and clock chain are analog blocks and are the most likely to have problems at temperature extremes. Chip assured us at the beta testers' meeting that considerable care was taken in the design of those circuits and left plenty of margin calculated for extremes of temperature. That is in line with what he just said in the manifesto about "why it works..."



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Chip Gracey
Parallax, Inc.

QuattroRS4
02-06-2007, 12:12 PM
Propeller_Head,
I take it that this proposed weather app. is going to be battery powered ? That will be a big consideration if it is the case as you are probably aware battery performance will be seriously diminished in extremes of cold. Its not just the prop for consideration here - at this temp. I would seriously consider a heat pump - If you plan to use adc's with a reference device - I have seen temps. affect the voltage reference components - thus affect accuracy of measurement..

Tracy Allen
02-07-2007, 12:04 AM
Yeh, -65 is almost the limit of a chamber cooled by LCO2, as -73 is the limit set by expansion of liquid at 900psi to gas at atmospheric pressure. I rarely take it so low, because near the extreme it consumes CO2 at a rapid rate, and, Mil Spec parts need to be characterised "only" down to -55 C. Not that I have to do that very often. A Nitrogen cooled chamber can go considerably lower, -180 Celsius. The chamber can also hit the high end, +125 Celsius or above.

It is true that other components in the system, the reference electronics or the battery or the packaging, can be critical in temperature extremes, and condensation on circuit boards can affect both accuracy and longevity.

A couple of weeks ago we were recording -22 Celsius at Crane Flat in Yosemite. It rarely gets that low here in California. At those temperatures the sealed PbAcid batteries are near their low limit, although the systems do have a temperature compensated float charger and the batteries have lots of reserve capacity. For really low temperatures the Lithium chemistries are better.

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Tracy Allen
www.emesystems.com (http://www.emesystems.com)

Propeller_Head
02-12-2007, 01:42 AM
I am planning on using the Propeller for my next Weather Balloon project (see www.geocities.com/Almost_There_Weather_Balloon/ (http://www.geocities.com/Almost_There_Weather_Balloon/)). There was a recent post that Parallax had tested down to -65* F; good enough. I am using Lithium batteries, which are rated down to -40* F (but, can still function below that at reduced capacity.)

The Propeller is way over-kill for this project, but I'm using it anyway. Right now I'm working on the Transmitter; last time it was out of range at about at about 40 miles or so - I need about three to four times that distance. I have a little 80 Meter Transmitter knocking out Morse Code, but haven't tested it for distance yet.




QuattroRS4 said...
Propeller_Head,
I take it that this proposed weather app. is going to be battery powered ? That will be a big consideration if it is the case as you are probably aware battery performance will be seriously diminished in extremes of cold. Its not just the prop for consideration here - at this temp. I would seriously consider a heat pump - If you plan to use adc's with a reference device - I have seen temps. affect the voltage reference components - thus affect accuracy of measurement..

steprog
02-12-2007, 06:03 AM
Hello,
Is there any thought to testing the propeller over mil specs?· I work with Fiber Optic Gyros and such and it would be nice to tell this to my customers.
Thanks,
Greg

Bean
02-12-2007, 08:59 AM
My company also make devices that need to go through the mil temp levels (-55C to +125C). So I would like to see it test down to -55C too.

Bean.

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Ken Peterson
03-26-2007, 10:20 AM
I am working on an automotive application for which the Propeller seems to be ideal. However, it needs to operate at temperatures from -40C to +85C. Have any tests been done at +85C? Seems the hotter temperatures would be more challenging for the processor than the lower ones...

Paul Baker
03-27-2007, 09:55 PM
Sorry I missed your post Ken, the preliminary datasheet will be out within a week's time. Unfortunately what differentiates this being the preliminary versus the final datasheet is temperature under bias testing. Shortly we should be receiving an environmental chamber at which point we can start these tests. We would be happy to release the results as they are known. We have every confidence that the chip will be able to perform under the conditions we will subject it to, the only thing·which we anticipate may happen is we may have to derate a few parameters (relax the stated value to ensure it is valid over the entire temperature range).

In regards to the hot vs. cold being the critcal factor, it all depends on the chip. Frequently it is the hotter temperatures that cause a chip to fail a fitness test, but this isn't always the case.

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

Post Edited (Paul Baker (Parallax)) : 3/27/2007 2:00:47 PM GMT

Ken Peterson
07-11-2007, 11:39 PM
By the way, the company I work for has their own test lab that they hire out as well. Just a plug...in case you need some testing done outside.

http://www.centerofengineering.com

--
Ken Peterson

KenBash
07-12-2007, 12:12 AM
I work with (clear) medical grade silicone. I'm not sure about the exact specs of this particular formula, but Dow Corning rates the operational temperature of most of its silicone products from -100 - 316 Centigrade. ( -148 to +600 F ) I haven't coated one of my propeller boards yet, but I have coated other electronics and it works great for both moisture and electrical insulation.

If condensation is a problem with systems out in the weather, you might want to try this as a coating.

I've been toying with using the Propeller for some things to do with SCUBA Diving. If anyone is interested, I'll coat a couple of boards and see how they survive a dunk in salt water. I'd also be interested in seeing what happens to these boards at the extremes of temperature as well.

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Paul Baker
07-12-2007, 02:51 AM
Ken P,
Thanks for the offer, we have an environmental chamber. We are just waiting for an electrician to rewire the 120V 20A dedicated outlet (should be any day now).

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)