Re: RPi-zero 2 W heat issues


David Ranch
 


Hello Vic,

I have had a Raspberry Pi-zero W for a while for portable digital ops...nice and compact and runs forever with low battery drain, but it is a bit slow.

Makes sense since it's basically a Rpi v1 with a single old ARM v6L core but without HDMI, wired Ethernet, etc.


So, when the zero 2 W came out, I was eager to swap it in the same little case. It is fantastic, FT8 decodes right away and Fldigi loads and runs well

It's basically a depopulated Raspberry Pi 3 with less RAM.  I'm surprised programs like these run very well at all with only 512MB of RAM.  Are you sure your Rpi isn't swapping when running say Fldigi?  Look at the "used" column when running the command line program "free".  It will never be zero but if it's consuming all of your configured swap, performance will be dramatically impacted and your SD card will fail far sooner than it should.     Btw, if you're not running the new Raspberry Pi OS "Bullseye" release yet, be warned as this will probably get harder to run big memory footprint programs with that OS version due to additional bloat.


...except for one thing. Running only Fldigi and Conky to monitor the processor the heat steadily rises relatively quickly until somewhere past 134F it shuts the thing off. Adding a heatsink helps, but the rise is inevitable and happens within 20 minutes or so, depending on ambient temperature, even with the Pi out of the case.

It all comes down to cooling.  You're doing the right things here.. hopefully that's a good heat sink with a good thermal pad (many cheap heatsinks have *terrible* thermal pads btw).  You might consider trying other BIGGER heatsinks or even entire-case heatsink cases like the FLIRC line of all-metal cases ( https://flirc.tv/more/flirc-raspberry-pi-zero-case ).  If your case+heatsink has good ventilation for the heat build up, maybe you need a fan for those high CPU draw scenarios.


I could add a small fan, but now I am defeating the size and power use benefit.

Instead of a full time fan, you might consider running a temperature controlled *variable* speed fan:   https://www.trinityos.com/HAM/CentosDigitalModes/RPi/rpi4-setup.html#60d.appendix-cases-fanctl .  The solution is quiet and only runs the fan fast enough to get the meet the temperature you set.


Note that this problem seems to be only with Fldigi, not any of the other programs like WSJT-X or LinPSK that run cool and work well. So my question is whether there is something I could do like underclocking to control temps when running this program? Any other ideas?

Underclocking and undervolting might be a possibility but it also might slow the Pi down enough that those applications won't run very well anymore:

   https://www.reddit.com/r/raspberry_pi/comments/aki1is/reducing_power_of_the_raspberry_pi_3_b/


There are other settings in Fldigi that might help here:

   - Turn on the "Slow CPU" feature - http://www.w1hkj.com/FldigiHelp-3.22/miscellaneous_configuration_page.html
   - Slow or outright stop the waterfall


--David
KI6ZHD

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