GPU/CPU temperature limit for RPI3

[jcozar87]

Hi everyone,

I am using the RPI3 and the picamera to process the video stream. The temperature of the CPU and GPU ranges from 50º to 72º Celsius, using or not a tiny fan (I am measuring these temperatures using the thermal_zone0/temp and vcgencmd measure_temp commands).

However, I wonder which one is the limit for the RPI3 in terms of temperature. I mean:

If I run the RPI3 8 hours per day, which one is the estimated useful life for the RPI3 if the temperature rounds the 70º Celsius? and if it is 50º Celsius?

Thank you very much.

[DougieLawson]

Limit is 85°C at which point it will throttle back until the temperature drops.

[jcozar87]

Thank you very much for your answer. It's good to know that my RPI is more than 10ºC away from that limit.

However, my question is more related to how many time the RPI might work until it is broken. In other words:

Suppose that my RPI is working 5 years (8 hours per day, 365 days) if the temperature is around 50ºC, until it is broken. How this time varies if the temperature while it is working is around 70ºC? From 5 to 3 years? Or maybe less than a year?

I know that these times are dependent on several factors, but the objective of my question is to know if it is worthy to put the fan on my RPI case or not. For example, if it varies from 5 to 3 years, maybe it is worthy for me not to use the fan.


Thanks!

[DougieLawson]

The current estimate is 30 years and more. Your SDCard will fail first.

[jahboater]

I know that these times are dependent on several factors, but the objective of my question is to know if it is worthy to put the fan on my RPI case or not. For example, if it varies from 5 to 3 years, maybe it is worthy for me not to use the fan.

Its not worth using a fan unless you are into extreme overclocking.
You could stick a small heat sink on with some decent (3M) thermal tape, and mount the Pi on edge (with the heat sink fins aligned vertically) which will give a few degrees of convection cooling without the noise and hassle of the fan.
Might even increase the lifetime from 30 years to 31 years, who knows?

[jcozar87]

Ok thank you! This is exactly what I wanted to know

[Pete6]

At risk of getting hammered for resurrecting this thread, I have a Pi 3B running an astronomy AllSky camera. The Pi is mounted inside a re-purposed dome security camera case. The whole thing is mounted on the gutter of my sun room which faces south. I have a DS18B20 sticking up into the sunlight 'cuz I am more interested in night time temperatures than daytime ones. However my CPU is currently reading 75C.

I know that when it hits 85C the GPU will throttle back but that ain't gonna stop the sun continuing to heat it up. Outdoor temeratures where I live regularly hit 34C in summer. Today it is 27C and I see the CPU at 75C say 90C? Actually I do not mind if it shuts down so long as it wakes up again in the cooler evening.

My script and raspistill use very little CPU. Mostly less than 2%.

Any ideas or advice please?

[jamesh]

At risk of getting hammered for resurrecting this thread, I have a Pi 3B running an astronomy AllSky camera. The Pi is mounted inside a re-purposed dome security camera case. The whole thing is mounted on the gutter of my sun room which faces south. I have a DS18B20 sticking up into the sunlight 'cuz I am more interested in night time temperatures than daytime ones. However my CPU is currently reading 75C.

I know that when it hits 85C the GPU will throttle back but that ain't gonna stop the sun continuing to heat it up. Outdoor temeratures where I live regularly hit 34C in summer. Today it is 27C and I see the CPU at 75C say 90C? Actually I do not mind if it shuts down so long as it wakes up again in the cooler evening.

My script and raspistill use very little CPU. Mostly less than 2%.

Any ideas or advice please?

What specifically are you asking for? What are you trying to avoid?

[Pete6]

What happens to my running programs and tasks when the CPU exceeds its temperature limit? This is about as concise as I can word what I'm asking.

Put another way. If the CPU temp exceeds its limits by maybe 10C , so 95C will the Pi just stop, slowdown, what? Once the temperature has cooled off a bit, will it reboot or stay hung, whatever? Does that help jamesh?

Right now the temperature is at 75C, You can see it running on screen here http://75.10.164.105:8082/

Thanks for your help

[rpdom]

It will slow down until the temperature drops to a safer level, then speed up again.

[Pete6]

That was pretty much what I had thought but I wished to be sure. Thanks.

I shall ultimately put this whole thing on top of a 25M radio mast which is about 45 miles from my house so maintenance will not be that easy.

[pfletch101]

It will slow down until the temperature drops to a safer level, then speed up again.

What if the ambient temperature is above the temperature that the control system regards as 'safer'?

[trejan]

What if the ambient temperature is above the temperature that the control system regards as 'safer'?

The SoC clocks will be permanently throttled back in that situation.

If the ambient temperature is > 70C then you'll be operating the Pi out of spec. The SoC is rated for -40C to 85C but have been tested in an oven at > 100C. The other parts like the USB chip are just commercial temperature range though which is only 0C to 70C. It'll likely to work okay at higher temperatures but no guarantees so do this at your own risk.

You need to check the ambient temperature in the enclosure. If it is just the SoC that is getting to ~72C then it is fine and no fan is needed. If the whole thing is heating up to 75C+ then it probably could do with a heatsink and/or fan.

[Pete6]

It has a heatsink. I really do not want to put a fan in the box for a few reasons:
- the box is currently weatherproof i.e. no internal/external air path for ventillation.
- If the fan fails then I am back where I am now.
- the outside air is often slightly greater than 40C. I know that is not 85C but the whole case is in full sunlight with the interior below the camera and facing the sun is painted matt black

I really think I am going to have to live with this and have it slow down in the summer daytime. After all I really want it working at night.

[Imperf3kt]

Can't place some form of sun shade over it so it is out of direct sunlight?

If this setup contains any batteries, they may explode at that temperature.

[rpdom]

A heatsink inside an air-tight enclosure will have little effect once it heats up. The heat has nowhere to go.

If the enclosure is made of metal then you could bond the heatsink to the inside of that and it will allow heat out.

[Pete6]

1. There are no batteries.
2. I can live with a slowdown as it is only during the day.
3. Neither heatsink or fan has much effect in a closed environment. That was why I originally asked the question.

I may consider a Peltier cell on the outside of the case as it is metal. The problem is that they need quite a bit of power and I am powering this via 4 (2x +12V and 2x -) unused wires in my CAT 5 Ethernet cable so as to only run one cable up the mast. This however will be a last ditch effort. I may just power down the device when it gets too hot. I could do that with an Arduino and a a DS18B20 to shut down the Pi when it gets too hot. and then wake it up again when T-amb gets more favourable.

Commercial camera doing the same thing have exactly the same problems. Sticking things out in the midday sun used to be the preserve of Englishmen and mad dogs. Maybe I'm one of 'em...

Thanks for all your help and explanations.

[rpdom]

As the case is metal, consider this:

Block of metal (with thermal paste) between Broadcom SoC and case interior.

Heatsink (if needed - it might not be) on case exterior (also with thermal paste).

[Pete6]

Yes, that might work.

It may be soon time to try these measures. I saved this single frame just now https://photos.app.goo.gl/HLesJCfncCeHKHrx5 As you can see the CPU temperature just hit 86C. It is still working. In two months time I expect the outdoor temperature to rise by a further 6-7C so the Pi is going to get warm. If you want to see it working, go to http://75.10.164.105:8082/and use the simple menu.

A larger enclosure with some forced ventilation may be necessary. I hop not. I do not like fans running where I cannot see them or change them and I really don't like humid air driven over my electronics. This air will also carry at least some dust up to the camera area.

My guess is that this will run but the electronics may not last that long. That said, I have a Pi 2 that has run my garden irrigation system for the last 5 years and that has sat outside (in a weatherproof box) with its power supply and an ethernet switch and it has never failed so maybe there is hope here.

[Pete6]

It just fell over and a power cycle does not bring the login: prompt back up in SSH and I cannot get to the web page. CPU Temp hit 87C just before failure.

I have a 2nd device running on the North side of my house and that is happily running at CPU temp of 51C.

I need to bring it down from the gutter where it is mounted to see what broke. I will do that tomorrow as I wish to see if it can be rebooted when the sun goes down and the temperature comes down. It could be the micro SD card has failed or the buck regulator board, whatever. I'll find out tomorrow. This may mean the end of my little project if it can't take the heat. If so I will look into using an Arduino. They may be more heat tolerant. Dunno yet.

[Pete6]

I bought the device indoors and left it for half an hour, plugged it in and... it came straight back up. I have not opened the case. Just gave it power and away it went.

I have no idea what stopped. All I know is that I now have a problem with my project. I currently have a single box design. It may be that I will need to move to a two box configuration and use a commercial either USB or IP weatherproof camera and case with the PI brought indoors.

I need to investigate further.

Edit: Looks like I exceeded the specs of the microSD card I have which is only to 85C. There are industrial cards and they go to 90C. However the SD card is probably a few degrees lower than the CPU since it is not being heated.

[jamesh]

Odd. The Pi should simply slow down if it hits 85, not crash. Something is not right. I assume you are not overclocking?

Pi3 should be capable of running at well over 100 without failing (we make sure they don't though). I think we test to 120 or so in an oven.

[Pete6]

No, I am not overclocking. This is odd.

What failed externally was that I could not get to the lightppd webpage on my LAN. I could also not get the the login prompt via SSH. I cannot use the console since it is mounted on the roof.

The software collects an image every 2 minutes and these are concatenated into a Day or Night video every 10 minutes and both these processes continued right the way through. One shot I have sky and the next my ceiling and the file timestamps are 2 minute contiguous, so the CPU did not stop. It looks from this that the ethernet interface may have taken a break. The CPU continued to work but the communications seems to have stopped.

My normal CPU load, from HTOP, is about 1% rising briefly every 10 mins as the jpg files are concatenated. This lasts about 15 seconds.

What do you think?

[Pete6]

It (whatever it happens to be) failed again today. The camera keeps taking images, one every two minutes, the PI keeps on concatenating them into a contiguous video and the filename timestamps are consistent with two minute intervals. Therefore the processor has not stopped. It seems, as yesterday, that the communications has failed. I use the RJ45 LAN port and can get no response when I Ping its address. Without reboot it came back up and then died later when the sun hit it.

I have ordered a new Pi 4 2GB and a new "Transcend Information 16GB High Endurance microSD Card" both of which will be here Sunday. Thanks Amazon.

I'll just replace the whole inside of my device and put it back up. This could be anything causing this from a connector thermally expanding, the same with the SD card, The only things I do know are that the camera still functions and the Pi has good power or it would have stopped.

[Imperf3kt]

I'm guessing (and this is purely guessing) that your voltage regulator is reaching its thermal limit and shutting down.