Raspberry Pi Cooling


#1

I recently moved my Raspberry Pi 3 to the attic next to my RP2. Now I’m getting heat warnings. I guess the RP3 gets hotter than the RP2. Surely this must be a common problem for people here locating their setups in the attic. What have you found to be an effective solution?

I’ll be eventually relocating mine outdoors, so the attic temperature will not be an issue, but I’d still like to install appropriate cooling.


#2

Several sellers on Amazon are selling Pi cooling kits that consist of a few heat syncs that attach to the chips and the reviews look pretty promising. That coupled with a fan case or just fan blowing air across them should do a pretty good job of keeping the Pi happy.


#3

I was getting hi-temp gripes on one of mine over the weekend – it was only 103F outside, and I had the sealed metal enclosure containing the Pi3, SDR, and POE board covered with a cardboard sun shade – the Pi3 was only hitting 70C! When the sun went down, it cooled off to under 50C.

Not sure what good a heat sink on the CPU would have done – I think CPU utilization was under 30%. A fan inside the enclosure would have turned it from a normal oven into a convection one, not sure what good that would have done.

If I go with this setup long term, I’ll probably mount the Pi3 board to the enclosure using a relatively thick sil-pad, which will conform to the bottom of the board and provide a reasonably low thermal resistance to the enclosure. (Bergquist Gap Pad VO Soft, great stuff but not cheap)

Device temps start hitting 90C and I worry. 70C is warm, but survivable. SanDisk on their website says their microSD and micrSDHC cards “are capable of surviving operating temperatures from -13ºF to 185ºF (-25ºC to 85 ºC).” I’d note that “survive” is not the same as “happy and long lived.”

Question: what’s FlightAware’s threshold for hi temp?

bob k6rtm


#4

Thanks for the detailed answer. My setup is still in the attic, which, unfortunately, gets much hotter than outside. I’ll eventually be setting up outside. In the man time, I think I’ll set up a clip fan aimed at the RP3. I had temps up to 75C that I noticed, reported by FA. Can I query the PA directly at the command line what the temperature is?


#5

Try this: vcgencmd measure_temp


#6

If you’re writing code you can get the current temperature from /sys/class/thermal/thermal_zone0/temp (divide by 1000 for degC). I was reading the value and storing it in a text file on a samba drive. My web server then picked up the value and displayed it. Now with collectd I just pull up the graph.

My RPi 3 is also in the attic and was getting over 80 degC with the stick-on heatsinks in a plastic case. I implemented two mitigations that are helping so far:

  1. Eleduino case with fan from Amazon helped a lot https://www.amazon.com/gp/product/B012GPCLR6/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1

  2. Set the ondemand governor parmeters so the processor would spend more time at 600 MHz. There are many ways to do this but my solution was to change /etc/init.d/raspi-config so up_threshold is 80 and sampling_down_factor is 200.

My attic gets very hot so I still think the RPi will be touching 80 as we get into the worst of summer heat (black asphalt shingles on the rrom - how is that a good idea?)


#7

In a sealed box, it would eventually turn into a convection oven, however in an open space attic, the air surrounding the Pi would likely be cooler than the processor temperature, so you could use the heat sync and fan to help dissipate some of the heat. The OP said they put their Pi in the attic, which is why I recommended that solution.

I’ve found that my SDRs are much more heat producing than my Pi3’s though, for whatever that’s worth. I’m actually considering not installing the SDR when I put my sealed plastic box outside (I was going to use it for dump978) due to the amount of heat that it’s generating and power that it’s consuming.


#8

I ty-wrapped a DS18b20 temperature sensor to the exterior of my ProStick and found that it tends to run around 20 degF above ambient. Actual circuitry inside would be warmer since the sensor is also exposed to ambient, but still runs quite a bit cooler than the Pi 3.


#9

Thanks. That worked perfectly. I just added a small fan directed at both Pis, and the temperature dropped about 15C in 5 minutes. Pi2 is showing 57C. Pi3 is showing 62C now during the hottest part of the day.


#10

Why is Pi3 using so much more CPU than Pi2? Sure, it’s seeing more aircraft, but not by that large of a margin.

EDIT: No, actually, that is incorrect. I had the screens backward. The left one is ARMv7 Processor rev 4 (v7l), which is the Pi3, and the right one is ARMv6-compatible processor rev 7 (v6l), which is the Pi2. The Pi3 has 4 processors, and the Pi2 has only one, according to /proc/cpuinfo/. Does that sound right? So CPU utilization is probably lower on the Pi3 because there are 4 times as many processors.


#11

Oops. What I’ve been calling a Raspberry Pi2 is actually a Raspberry B+. Seems the Pi2 is also quad core. So, as of this writing, the temps are now 56.2C for the B+ and 60.7C for the 3. CPU utilization is 42%, and 5%, respectively. Dump1090 is using 34%, and 17%, respectively.


#12

When I put my older SDRs in metal cases, I used the aforementioned SIl Pad material between the SDR board and the $15 NooElec metal enclosure, which took the SDR operating temperature down a noticeable few degrees. I’ve also put pieces of Sil Pad on both sides of the board and then wrapped it with copper tape, providing shielding and more surface area for heat dissipation.

And that’s another issue to consider, the SDR clock drift with temperature – and in this situation, having the SDR run hotter than the environment actually helps, as the temperature stays more stable at that high end.

We’re going to a friend’s place on the 4th, they’re on the other side of the valley from us. I may take the portable setup I used on Field Day and try running it there to see what we can see…

bob k6rtm


#13

@k6rtm
did you try a small fan circulating air between the case and cardboard outer, might just e enough


#14

Only had one small fan with me, and it was blowing air over me! that and the box is sealed and uses PoE, so no way to power a fan on the outside. I’ll be posting pictures of the setup tomorrow or the next day. It was fun, and now that it works, I’ll probably leave it together for a while.

bob k6rtm


#15

Here’s a nice little CLI utility that may be of interest in tracking some metrics on your Pi’s. Does the VideoCore command calls for you and has a nice presentation of the data.

https://github.com/MilhouseVH/bcmstat