epoch1970
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Max ambient temperature for reliable operation of Pi 3?

Sat Feb 25, 2017 12:52 pm

I've been reading this interesting thread about maximum ambient temperature for operation in a sealed box, but it concentrates on CPU temp.

I am considering a system where the CPU is mildly loaded. This would be a Pi 3 wearing a HAT. I'd like to have your views of the maximum ambient temperature it could reliably operate at considering the system as a whole. That is: including an SD (prolly a Sandisk, largely idle as well) and an active ethernet connection, but excluding power supply.

To put it simply: if a Pi 3 bakes at 60°C (140°F) ambient, does it stop working, or does it "melt down"? What is the sustained ambient temperature level that would probably damage it or shorten its life ?

Thanks in advance for your views.
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wildfire
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Re: Max ambient temperature for reliable operation of Pi 3?

Sat Feb 25, 2017 4:15 pm

Probably best asking if a Pi can reliably work under a certain tempreture (subtle but a different question).

The Pi will throttle down when overheating occurs but obviously this will have limits.

You could always use liquid cooling or even more exotic methods if you beleive ambient tempreture will be a problem.
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DavidS
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Re: Max ambient temperature for reliable operation of Pi 3?

Sat Feb 25, 2017 5:39 pm

If you clock the CPU down to around 250MHz, the GPU to around 150MHz, and the RAM down to around 125MHz you may be able to get away with long term use at temperatures as high as 70 C ambient. MAYBE, just MAYBE.

Though I do not know how much would be damaged, and how much of the RPi would still be usable. I would expect that the SoC could remain usable, as well as the RAM, likely the GPIO will do well as well, though I would not rely on much else. Even the voltage regulators may be an issue, so you may end up needing to figure how to work around that. I would not expect the USB hub with its integrated Ethernet to last very long at that high of an ambient operating temperature, not sure about what is between the SoC and HDMI port, though that may or may not be usable.
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W. H. Heydt
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Re: Max ambient temperature for reliable operation of Pi 3?

Sat Feb 25, 2017 9:51 pm

DavidS wrote:If you clock the CPU down to around 250MHz, the GPU to around 150MHz, and the RAM down to around 125MHz you may be able to get away with long term use at temperatures as high as 70 C ambient. MAYBE, just MAYBE.
A major supplier site I was looking at yesterday gave the operating temperature range as -25C to +80C for the CM3, and that has the core parts of the Pi3B...the SoC and the DRAM.

peterlite
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Re: Max ambient temperature for reliable operation of Pi 3?

Sat Feb 25, 2017 11:39 pm

Disks often have a top temp of 40c for reliable operation. The things you plug in will be the main problem because many will not throttle down when hot, they will fail.

There are several posts about thermally controlled fans. Always a good idea when the temperature goes over 30c.

Another approach is to leave an egg on top. It might not stop your hardware melting down but you do end up with a cooked breakfast. :)

epoch1970
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Re: Max ambient temperature for reliable operation of Pi 3?

Sun Feb 26, 2017 12:44 am

Thanks for your comments, all.
No spinning HDD, no USB devices... but I am pretty sure ethernet will stop working properly well before 70°C.
I would hate to add active ventilation, but certainly I can use the internal CPU temp sensor in conjunction with average load to make the system complain loudly when it gets too hot, and shutdown after that. Or better, wire an ambient temp sensor.
The machine will be indoors but largely unattended, so I need to handle the situation where somehow it ends up in an unsafe environment. I don't think 50°C ambient would be reached under nominal conditions, but that's just a guess right now.
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