7 ms·

Thermal engineer here. There absolutely no need to use fan cooling, humongous heatsinks or harebrained temperature controller schemes to cool the raspberry pi 4

Thermal engineer here. There absolutely no need to use fan cooling, humongous heatsinks or harebrained temperature controller schemes to cool the raspberry pi 4. All that is needed is a small heatsink to slightly decrease the thermal resistance to ambient air, to stay below the thermal throttling threshold. Anything more complicated than that is a pointless exercise in pointlessness.

jstanley 6y ago
This is basically an appeal to authority. You haven't explained what property of the Raspberry Pi 4 means that a tiny heatsink is sufficient. Why can't I just replace the words "raspberry pi 4" with anything else and conclude that I never need fans or large heatsinks?
- Spivak 6y ago
  Because you can see in the graphs that the bare pi doesn’t get that hot. If you allow just a bit more heat to escape you push the graph down to where the peak sits just below the throttling point. For home/hobby use this doesn’t matter too much but you typically want to run as hot as allowable. It’s a win-win since small heat sinks are cheap and don’t have any moving parts.
  - StillBored 6y ago
    Running 32-bit raspbian... Try that with a 64-bit OS, running 64-bit compiles/etc. I have a huge heatsink on mine (40mm cube), and even without the overclock it will crank up to 80C doing long running compiles. Running it at 80C for an hour or two, the temp of everything on the board starts to approach 80C. Touching the usb ports at that point will give you a surprise. So, I added a small 20mm fan, and set the profile to kick on at 60C, which generally keeps the soc thermals in the 60-70C range. No throttling, and still no noise because with that large of a heatsink it doesn't take much air to cool it. Add in a couple hundred Mhz of overclocking and that fan stays on pretty much all the time.
throwaway-9320 6y ago
Fan cooling a Raspberry Pi 4 is such an odd thing to do. You are essentially taking one of the pros of the Pi - quiet and reliable operation - and replacing it with a moving part that will not offer too much benefit and will eventually wear out or start having issues.
- willis936 6y ago
  As someone who uses pis and MCUs, I don’t find anything that relies on a micro sd card to be reliable.
  - vardump 6y ago
    You can USB or network boot a Pi. Also in my experience over 9 years: just don't use Sandisk cards and you're fine. Samsung (Pro|Evo) branded cards have worked for me.
    - willis936 6y ago
      Network boot adds even more points of failure. USB boot is very attractive, but also very new. I’ll play around with it once it’s out of beta and the setup procedure is established. I use Samsung Evo cards and haven’t had an issue with them either. My problem is one of confidence. I have no data to suggest that these cards won’t just hard fail at some point in the next five years. Simply doing better than their competitors in the micro SD card space is not good enough.
      - megous 6y ago
        All of the dead cards, if I open my drawer where I store them marked with a black cross-mark, are samsung evo cards. All my Sandisk Ultras (the real ones verified on Sandisk's chinese website) are still running fine after ~3-4 years of usage. Anyway, Samsung Evos didn't hard fail for me. They just stopped executing writes (without reporting any errors). So your system seems to work (for a while), but after reboot it's back to where it was previously. It's a pretty stupid way to handle end-of-life condition for the card. I wish samsung decided to report write failures instead of simply ignoring the writes and reporting success.
ybbond 6y ago
My issue with heat management is dust (on fan), also I live in the equator line area that makes it very hot in the afternoon (makes heat sink less effective). That makes me think a lot before choosing passive or active cooling. The Flirc case-as-heatsink one seems good tho, and on-line with your statement
encom 6y ago
I kind of agree. I think in most situations, a Pi is going to sit idle most of the time, so it won't need active cooling.
- larme 6y ago
  What if I want to use pi 4 as a building farm? Especially now with the 8gb version out, it seems to be suitable for building haskell programms
  - gambiting 6y ago
    Well then I'd say sure, of course you need cooling. But I'd also guess that you're within <1% of Rpi users who actually need cooling, and I'd guess that's also why Rpi doesn't come with a radiator by default - vast majority of users simply don't need one and it would increase the cost.
  - jdsully 6y ago
    I use my pi 4 as part of a build farm with a 2cm tall passive heatsink. It never goes above 65c.
    - StillBored 6y ago
      64-bit kernel, or 32-bit?
      - jdsully 6y ago
        32
  - jrockway 6y ago
    It's a really, really slow computer. The Pi 4 is something like 10x faster than the original Raspberry Pi, but that was also a really, really slow computer. I remember not wanting to set up a cross compiler once, and recompiled ntpd on one. It took more than 24 hours. The same build runs on my desktop in seconds. It is good for things like reading a sensor and sending it to some server, but so are ESP32s which are cheaper. You are paying a heavy price to get video output and Linux compatibility. In the current era, it's a bad microcontroller (expensive!) and a bad desktop computer (slow!). When it came out, most people were using $25 MCU boards, so $10 extra to run Linux was a great deal. These days, a massively more capable MCU dev board can be had for $4 (if you want free 2 day shipping, less if you can wait).
Arnt 6y ago
Would you describe that flirc case as complicated? To a naïve layman, it seems like the smallest all-metal case that'll fit the rpi4, made so that the metal acts as a heatsink. Which may be more heatsink area than a 15W CPU needs, but not bigger case area than is needed. Is there something I'm missing?
- smichel17 6y ago
  I got a pi 4 around 6 months ago and got the flirc case based on the recommendation of TFA. I've been very pleased with it - makes the pi look nice; I no longer worry about other people touching it; and of course it cools well (the very thick thermal pad connecting to the case is a bit unusual, but it works). I got the flirc usb dongle for remotes at the same time, since I thought I'd want it (my pi is a media center) and there was a discount at the time if you bought both it and the case.. I've been far less impressed. It's a great idea in theory, but in my experience there was enough flakiness/delay with each button press, especially with Kodi for some reason, that it was basically unusable. Also, their utility for programming the dongle did not run well on the pi itself (it stores configuration on-device so you don't need to program it from the device you'll be using it on), and the install process involved setting up a repo that is served over http and does not have an associated gpg key, which gave me a bad feeling (although overall it felt more like a startup flying by the rest of its pants than anything malicious). I am somewhat hopeful that with more time/polish these issues will be fixed in software, but can't currently recommend it.
  - ja27 6y ago
    Kinda wish the top of the FLIRC case wasn't rubberized. My older one is sticky now, but that might be more of an issue in Florida humidity. Still got one for a Pi 4 and it ran well enough.
- NortySpock 6y ago
  I believe the FLIRC case is custom designed for the RPi4, not just "happens to fit" as you imply. Otherwise you have it correct; it's an aluminum case that mates down onto the CPU for direct passive cooling. Note that it's clearly an injection-molded aluminum top-half and the bottom-half is plastic, just used to keep the dust out. I would describe it as simple and elegant; fit for purpose. Otherwise I'm quite happy to have a full passive cooling config, as currently my RPi home server must live in the kitchen/dinning room area due to space constraints.
yipbub 6y ago
Can you qualify your statement (please)?
miro-siagi 6y ago
In what case should I care about fan cooling then? How are electronic components affected by temperature in general?
hajile 6y ago
Somebody's never overclocked their pi before... With an overclock, even a FLIRC would throttle when running our full unit test suite. A 30% reduction in unit test runtime is nothing to sneeze at and I certainly didn't want to downclock to 600-800MHz due to throttling. An ICE Tower was a lifesaver.
- arbitrage 6y ago
  by overclock, do you mean full-out running at peak all the time? or letting the CPU governor still work and just bumping up the limits? one makes sense, the other is hubris.
  - hajile 6y ago
    In theory, TDP scales linearly with clockspeed. In practice, power increases higher than that rate. 30-35% increases in heat to dissipate is significant. I'm old school when it comes to overclocking. Stability and sustainability matter to me. I don't always run all cores full-on for hours, but when I do, I want a cooling solution that's up for the job.
LeoPanthera 6y ago
Did you read the article? He tested a heatsink. I'll quote the relevant part. > Heatsinks will generally shave 5-10°C off the highest temperatures you encounter, which is significant, but you still need to have air moving across the heatsink for it to do anything. This means either a fully open Pi (great for testing or tinkering, not so great for a semi-permanent installation), a well-ventilated case (with slots or holes in the bottom and top to allow natural convection), or a fan. So not a bad choice, and they're so cheap you should probably stick them on any Pi you can... but heatsinks alone won't solve Pi cooling problems.
- washadjeffmad 6y ago
  He doesn't have much of a methodology and seems to have missed a key point of the heatsink: orientation. If he'd mounted his Pis' GPIO parallel to the ground, heatsink fans perpendicular to it, he would have found his missing convection with or without a heatsink. This is what I do, and mine haven't reported >45`F ambient under peak load in a passively ventilated area. There is no issue with heat removal with enough air space.

jstanley 6y ago

This is basically an appeal to authority. You haven't explained what property of the Raspberry Pi 4 means that a tiny heatsink is sufficient. Why can't I just replace the words "raspberry pi 4" with anything else and conclude that I never need fans or large heatsinks?

Spivak 6y ago
Because you can see in the graphs that the bare pi doesn’t get that hot. If you allow just a bit more heat to escape you push the graph down to where the peak sits just below the throttling point. For home/hobby use this doesn’t matter too much but you typically want to run as hot as allowable. It’s a win-win since small heat sinks are cheap and don’t have any moving parts.
- StillBored 6y ago
  Running 32-bit raspbian... Try that with a 64-bit OS, running 64-bit compiles/etc. I have a huge heatsink on mine (40mm cube), and even without the overclock it will crank up to 80C doing long running compiles. Running it at 80C for an hour or two, the temp of everything on the board starts to approach 80C. Touching the usb ports at that point will give you a surprise. So, I added a small 20mm fan, and set the profile to kick on at 60C, which generally keeps the soc thermals in the 60-70C range. No throttling, and still no noise because with that large of a heatsink it doesn't take much air to cool it. Add in a couple hundred Mhz of overclocking and that fan stays on pretty much all the time.

throwaway-9320 6y ago

Fan cooling a Raspberry Pi 4 is such an odd thing to do. You are essentially taking one of the pros of the Pi - quiet and reliable operation - and replacing it with a moving part that will not offer too much benefit and will eventually wear out or start having issues.

willis936 6y ago
As someone who uses pis and MCUs, I don’t find anything that relies on a micro sd card to be reliable.
- vardump 6y ago
  You can USB or network boot a Pi. Also in my experience over 9 years: just don't use Sandisk cards and you're fine. Samsung (Pro|Evo) branded cards have worked for me.
  - willis936 6y ago
    Network boot adds even more points of failure. USB boot is very attractive, but also very new. I’ll play around with it once it’s out of beta and the setup procedure is established. I use Samsung Evo cards and haven’t had an issue with them either. My problem is one of confidence. I have no data to suggest that these cards won’t just hard fail at some point in the next five years. Simply doing better than their competitors in the micro SD card space is not good enough.
    - megous 6y ago
      All of the dead cards, if I open my drawer where I store them marked with a black cross-mark, are samsung evo cards. All my Sandisk Ultras (the real ones verified on Sandisk's chinese website) are still running fine after ~3-4 years of usage. Anyway, Samsung Evos didn't hard fail for me. They just stopped executing writes (without reporting any errors). So your system seems to work (for a while), but after reboot it's back to where it was previously. It's a pretty stupid way to handle end-of-life condition for the card. I wish samsung decided to report write failures instead of simply ignoring the writes and reporting success.

ybbond 6y ago

My issue with heat management is dust (on fan), also I live in the equator line area that makes it very hot in the afternoon (makes heat sink less effective). That makes me think a lot before choosing passive or active cooling. The Flirc case-as-heatsink one seems good tho, and on-line with your statement

encom 6y ago

I kind of agree. I think in most situations, a Pi is going to sit idle most of the time, so it won't need active cooling.

larme 6y ago
What if I want to use pi 4 as a building farm? Especially now with the 8gb version out, it seems to be suitable for building haskell programms
- gambiting 6y ago
  Well then I'd say sure, of course you need cooling. But I'd also guess that you're within <1% of Rpi users who actually need cooling, and I'd guess that's also why Rpi doesn't come with a radiator by default - vast majority of users simply don't need one and it would increase the cost.
- jdsully 6y ago
  I use my pi 4 as part of a build farm with a 2cm tall passive heatsink. It never goes above 65c.
  - StillBored 6y ago
    64-bit kernel, or 32-bit?
    - jdsully 6y ago
      32
- jrockway 6y ago
  It's a really, really slow computer. The Pi 4 is something like 10x faster than the original Raspberry Pi, but that was also a really, really slow computer. I remember not wanting to set up a cross compiler once, and recompiled ntpd on one. It took more than 24 hours. The same build runs on my desktop in seconds. It is good for things like reading a sensor and sending it to some server, but so are ESP32s which are cheaper. You are paying a heavy price to get video output and Linux compatibility. In the current era, it's a bad microcontroller (expensive!) and a bad desktop computer (slow!). When it came out, most people were using $25 MCU boards, so $10 extra to run Linux was a great deal. These days, a massively more capable MCU dev board can be had for $4 (if you want free 2 day shipping, less if you can wait).

Arnt 6y ago

Would you describe that flirc case as complicated? To a naïve layman, it seems like the smallest all-metal case that'll fit the rpi4, made so that the metal acts as a heatsink. Which may be more heatsink area than a 15W CPU needs, but not bigger case area than is needed. Is there something I'm missing?

smichel17 6y ago
I got a pi 4 around 6 months ago and got the flirc case based on the recommendation of TFA. I've been very pleased with it - makes the pi look nice; I no longer worry about other people touching it; and of course it cools well (the very thick thermal pad connecting to the case is a bit unusual, but it works). I got the flirc usb dongle for remotes at the same time, since I thought I'd want it (my pi is a media center) and there was a discount at the time if you bought both it and the case.. I've been far less impressed. It's a great idea in theory, but in my experience there was enough flakiness/delay with each button press, especially with Kodi for some reason, that it was basically unusable. Also, their utility for programming the dongle did not run well on the pi itself (it stores configuration on-device so you don't need to program it from the device you'll be using it on), and the install process involved setting up a repo that is served over http and does not have an associated gpg key, which gave me a bad feeling (although overall it felt more like a startup flying by the rest of its pants than anything malicious). I am somewhat hopeful that with more time/polish these issues will be fixed in software, but can't currently recommend it.
- ja27 6y ago
  Kinda wish the top of the FLIRC case wasn't rubberized. My older one is sticky now, but that might be more of an issue in Florida humidity. Still got one for a Pi 4 and it ran well enough.
NortySpock 6y ago
I believe the FLIRC case is custom designed for the RPi4, not just "happens to fit" as you imply. Otherwise you have it correct; it's an aluminum case that mates down onto the CPU for direct passive cooling. Note that it's clearly an injection-molded aluminum top-half and the bottom-half is plastic, just used to keep the dust out. I would describe it as simple and elegant; fit for purpose. Otherwise I'm quite happy to have a full passive cooling config, as currently my RPi home server must live in the kitchen/dinning room area due to space constraints.

yipbub 6y ago

Can you qualify your statement (please)?

miro-siagi 6y ago

In what case should I care about fan cooling then? How are electronic components affected by temperature in general?

hajile 6y ago

Somebody's never overclocked their pi before... With an overclock, even a FLIRC would throttle when running our full unit test suite. A 30% reduction in unit test runtime is nothing to sneeze at and I certainly didn't want to downclock to 600-800MHz due to throttling. An ICE Tower was a lifesaver.

arbitrage 6y ago
by overclock, do you mean full-out running at peak all the time? or letting the CPU governor still work and just bumping up the limits? one makes sense, the other is hubris.
- hajile 6y ago
  In theory, TDP scales linearly with clockspeed. In practice, power increases higher than that rate. 30-35% increases in heat to dissipate is significant. I'm old school when it comes to overclocking. Stability and sustainability matter to me. I don't always run all cores full-on for hours, but when I do, I want a cooling solution that's up for the job.

LeoPanthera 6y ago

Did you read the article? He tested a heatsink. I'll quote the relevant part. > Heatsinks will generally shave 5-10°C off the highest temperatures you encounter, which is significant, but you still need to have air moving across the heatsink for it to do anything. This means either a fully open Pi (great for testing or tinkering, not so great for a semi-permanent installation), a well-ventilated case (with slots or holes in the bottom and top to allow natural convection), or a fan. So not a bad choice, and they're so cheap you should probably stick them on any Pi you can... but heatsinks alone won't solve Pi cooling problems.

washadjeffmad 6y ago
He doesn't have much of a methodology and seems to have missed a key point of the heatsink: orientation. If he'd mounted his Pis' GPIO parallel to the ground, heatsink fans perpendicular to it, he would have found his missing convection with or without a heatsink. This is what I do, and mine haven't reported >45`F ambient under peak load in a passively ventilated area. There is no issue with heat removal with enough air space.