mrbijan
Posts: 3
Joined: Thu Oct 18, 2018 10:45 am

Fan with no heatsink

Thu Oct 18, 2018 10:51 am

Hi

I've searched the internet up and down for an answer.
Unfortunately all the answers talk about heatsinks.

My question is, will putting a fan with no heatsink do any good on my Pi 3 B+?

Thanks :)

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mahjongg
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Location: South Holland, The Netherlands

Re: Fan with no heatsink

Thu Oct 18, 2018 11:16 am

Yes, obviously.

The heat spreader over the SoC, acts like a limited "heat sink", but without optimizing the surface area that is exposed to air flow.
Blowing air over it will obviously have an effect, just not a much as when you would have a piece of heat transferring matter (the "heat sink)" on top of it that increases the surface area exposed to air.
Also, as the heat spreader uses the PCB's ground plane to spread the heat all over the PCB, blowing air over all that surface also helps dissipating the heat away from the SoC.

mrbijan
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Joined: Thu Oct 18, 2018 10:45 am

Re: Fan with no heatsink

Thu Oct 18, 2018 11:22 am

Thanks for your reply :)

My fan is pulling air from the case instead of pushing, I've read that is more effective.
Is this still the case, when running with no heatsink?

Idahowalker
Posts: 372
Joined: Wed Jan 03, 2018 5:43 pm

Re: Fan with no heatsink

Thu Oct 18, 2018 12:26 pm

mrbijan wrote:
Thu Oct 18, 2018 11:22 am
Thanks for your reply :)

My fan is pulling air from the case instead of pushing, I've read that is more effective.
Is this still the case, when running with no heatsink?
Positive or Negative air pressure, that is the question.

My view, I use positive air pressure over negative air pressure because, over the air intake of the fan, I can put a dust filter, which I can clean from time to time. With negative air pressure, I am relying on tiny air leaks in the case to provide moving air to my project. If those tiny air holes get clogged with dust, I will have to disassemble the project and hunt those clogged air holes down to clean them.
Without knowing why you are deleting my postings, I will not know how...

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mahjongg
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Re: Fan with no heatsink

Thu Oct 18, 2018 12:30 pm

Except for the point of dust filtering, air flow is air flow.... The point is replacing warmed up air with new cool air, its not rocket science.

jahboater
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Joined: Wed Feb 04, 2015 6:38 pm

Re: Fan with no heatsink

Thu Oct 18, 2018 3:23 pm

Have you established that you actually "need" any additional cooling? (Is it definitely throttling?)

The 3B+ has very good thermal management built-in which should be enough for smallish work loads.

Secondly do you really need a fan? A good passive heat sink is quieter and simpler and entirely adequate.

To see whats happening, run this script while your program(s) are running and see.

Code: Select all

#!/bin/bash
Counter=14
DisplayHeader="Time      Temp    CPU        Throttle       Vcore"
while true ; do
  let ++Counter
  if [ ${Counter} -eq 15 ]; then
    echo -e "${DisplayHeader}"
    Counter=0
  fi
  Health=$(perl -e "printf \"%19b\n\", $(vcgencmd get_throttled | cut -f2 -d=)")
  Temp=$(vcgencmd measure_temp | cut -f2 -d=)
  Clockspeed=$(vcgencmd measure_clock arm | awk -F"=" '{printf ("%0.0f",$2/1000000); }' )
  CoreVoltage=$(vcgencmd measure_volts | cut -f2 -d= | sed 's/000//')
  echo -e "$(date '+%H:%M:%S') ${Temp} $(printf '%4s' ${Clockspeed})MHz $(printf '%019d' ${Health}) ${CoreVoltage}"
  sleep 10
done
If the CPU stays at 1400MHz under load, then no heat sink is needed (it will drop down to 600MHz at idle).

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Imperf3kt
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Location: Australia

Re: Fan with no heatsink

Thu Oct 18, 2018 7:04 pm

I don't know about inside a case, but I can say that a fan blowing air on a Pi is a hundredfold more effective than blowing it off, in free air.
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

mrbijan
Posts: 3
Joined: Thu Oct 18, 2018 10:45 am

Re: Fan with no heatsink

Fri Oct 19, 2018 7:54 am

jahboater wrote:
Thu Oct 18, 2018 3:23 pm
Have you established that you actually "need" any additional cooling? (Is it definitely throttling?)

The 3B+ has very good thermal management built-in which should be enough for smallish work loads.

Secondly do you really need a fan? A good passive heat sink is quieter and simpler and entirely adequate.

To see whats happening, run this script while your program(s) are running and see.

Code: Select all

#!/bin/bash
Counter=14
DisplayHeader="Time      Temp    CPU        Throttle       Vcore"
while true ; do
  let ++Counter
  if [ ${Counter} -eq 15 ]; then
    echo -e "${DisplayHeader}"
    Counter=0
  fi
  Health=$(perl -e "printf \"%19b\n\", $(vcgencmd get_throttled | cut -f2 -d=)")
  Temp=$(vcgencmd measure_temp | cut -f2 -d=)
  Clockspeed=$(vcgencmd measure_clock arm | awk -F"=" '{printf ("%0.0f",$2/1000000); }' )
  CoreVoltage=$(vcgencmd measure_volts | cut -f2 -d= | sed 's/000//')
  echo -e "$(date '+%H:%M:%S') ${Temp} $(printf '%4s' ${Clockspeed})MHz $(printf '%019d' ${Health}) ${CoreVoltage}"
  sleep 10
done
If the CPU stays at 1400MHz under load, then no heat sink is needed (it will drop down to 600MHz at idle).
I haven't tried on the 3B+, but from my experience on 3 I needed extra cooling. Kept getting the temp icon on the screen.
Will try your script, thanks :)

jahboater
Posts: 3027
Joined: Wed Feb 04, 2015 6:38 pm

Re: Fan with no heatsink

Fri Oct 19, 2018 8:14 am

mrbijan wrote:
Fri Oct 19, 2018 7:54 am
I haven't tried on the 3B+, but from my experience on 3 I needed extra cooling. Kept getting the temp icon on the screen.
Will try your script, thanks :)
The new 3B+ is much better than the 3. Thermal management was a major part of the design.
You can see the silver heat spreader on top of the SoC.
The entire copper PCB ground plane acts as a heat sink - so you may even get a little extra cooling by plugging things into the sockets, which might be handy for a small case.

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