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Thread: Pitastic

  1. #91
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by chill View Post
    I was interested to see how to control a simple fan in software. To date my RPi4 seems to run comfortably cooler than the throttling temperature, but having developed a way to mount a fan in my 'stack' inside my amplifier, I was keen to see if I could leave it permanently connected but only have it running when needed.

    My simple 2-wire fan draws about 45mA on 3.3V, which is too much to drive directly from a GPIO pin. So I wired up a little transistor to switch the GND side of the fan according to the state of a GPIO pin. I made it so that it simply plugs into the existing fan wiring.





    Then I made a script to turn the fan on and off according to temperature. I set the 'off' temperature one degree below the 'on' temperature to reduce the frequency that it turns on and off.

    Here's the result from an idling pCP (no LMS, no Squeezelite) in the open air. When running at 3.3V the fan takes about 5 minutes to pull the temperature down from a resting 56 degrees to the 40 degrees that I set, then it sits at that temperature, with the fan coming on and going off as necessary. It struggles to get much below that. Running on 5V it cools faster and lower, but it becomes audible.


    Nice Job !
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezeLite-X,PiCorePlayer x3
    Server: LMS Version: Latest Nightly on Centos 7.6 VM on ESXi 6.5.0U3 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud/Spotty/Player Groups
    Remotes: iPeng9/Orangesqueeze/PC/Jivelite/SqueezeLite-X
    Music: 522GB,1.5K albums with 25K songs by 5K artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

  2. #92
    Senior Member chill's Avatar
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    A quick observation about heatsinks and their connection to the CPU. When I first fitted my 40mm x 40mm heatsink I used some 'thermally conductive tape'. It seemed to work, but I was suspicious because it seems to be about 1mm thick, and internally it seems to have a foam construction. I can't see how that can be good for thermal transmission.

    So I reaffixed the heatsink using a small blob of silicone heatsink compound. I wasn't sure it would work in my application, as my RPi is mounted on edge and the heatsink is fairly heavy, and I don't think the compound 'sets'. But it seems to be holding perfectly, and the better thermal contact has had a noticeable effect.

    With my fan turned on at 12:47, the temperature dropped by about 10 degrees in 4 minutes - that's about twice the drop I recorded when the heatsink was fixed with thermal tape. The non-fan temperature of 61 degrees is also about 3-4 degrees lower than the same test with thermal tape.


    This is the earlier test with the heatsink held on with thermal tape. Identical test conditions - if anything, the ambient temperature is warmer today.


    Perhaps the thermal conductive tape should be renamed 'thermal insulating tape'.

  3. #93
    Senior Member Jeff07971's Avatar
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    Had exactly the same experience with some small (Pi2/3) heatsinks that had "Genuine 3M heat tranfer tape"
    Does not sound like the stuff you had though as it was very thin (Like sellotape almost) but was BAD at heat transfer

    Got some HY910 thermal adhesive from ebay for a couple of quid, works much better

    Jeff
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezeLite-X,PiCorePlayer x3
    Server: LMS Version: Latest Nightly on Centos 7.6 VM on ESXi 6.5.0U3 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud/Spotty/Player Groups
    Remotes: iPeng9/Orangesqueeze/PC/Jivelite/SqueezeLite-X
    Music: 522GB,1.5K albums with 25K songs by 5K artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

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