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My Raspberry Pi 3B Plus is running Raspberry Pi OS (32-bit) Lite. I only made update, upgrade and install Apache2.

It is connected to my home network with 1Gb Ethernet cable (no WiFi). Network traffic to the RPi is virtually 0 Mbps.

There is no heatsink installed.

My htop is the following:

htop

Which looks like it's almost free of any task.

However it is pretty hot. I can barely hold my finger on SoC and network chips. My thermal imager shows this:

thermal img1

thermal img2

(Note that the dark squares on the top image are reflective surfaces - which always looks dark on thermal images)

Highest temperature is 51°C with ambient 28°C.

I dont't have anything to measure current consumption, but I'd say that it is far more than normal. I remember that in idle my RPi 3B Plus was just warm a little bit.

  • What can I do to debug this situation?
  • What can I do to decrease power consumption?
  • What else besides SoC can contribute to the power consumption?
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51 deg C is actually reasonably cool for a Pi3. My Pi4 regularly runs at over 60 deg C. Don't worry about it.

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  • Can i decrease cpu frequency or anything else to make it cooler? – Roman Matveev Jul 6 '20 at 15:25
  • Why do you want it to run cooler? – CoderMike Jul 6 '20 at 15:26
  • It runs into PLA 3d printed case and if it run more cpu demanding task or will be laced into warmer environment it can damage the case. – Roman Matveev Jul 6 '20 at 15:28
  • I would suggest a 3d printed case that can be affected by heat is not appropriate for a Pi. – CoderMike Jul 6 '20 at 15:29
  • Besides, if this amount of energy is not necessary, why spend extra energy? – Roman Matveev Jul 6 '20 at 15:31
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Like others said, 50°C is reasonable. I would not worry too much.

However, there are some things that you can do to decrease power consumption/temperature:

  • disable some services which you don't need to lessen the load (e.g. I disabled bluetooth & wifi because I only use ethernet cable)
  • underclock with arm_freq in config.txt - maybe underclock your GPU as well?
  • install a small (or big) heatsink
  • update firmware as addition to updating your kernel (check rpi-update which does both)
  • disable LED lights
  • Disable HDMI if you don't need it
  • blow at your RPI to decrease the temperature by a few degrees temporarily

Note: You can monitor the CPU temperatures with vcgencmd measure_temp. Makes all the blowing at your RPI more fun.

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  • Additionally I was able to turn off HDMI which lowered the temperature by 3 degrees or so. By far it was the only thing I was able to spot any difference. What else did I try: lowered cpu freq to 400MHz, turned off WiFi and Bluetooth. – Roman Matveev Jul 8 '20 at 13:51
  • 1
    Right, I forgot about HDMI - I never close it since I use it a lot. Interesting, 3 degrees is quite a lot, it would be nice to see some tests if turning it off helps performance as well. – GChuf Jul 8 '20 at 14:00
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My 3b+ feels a lot warmer than my plain old 3b: they are both idling most of the time. In fact they spend over 95% of their life idling. They are both housed in metal FLIRC cases. My point is, I don't want to pay for a heater: it's a waste of electricity. I just want a cool, efficient Raspberry Pi that I can leave on all the time and use as a git server for my home network. The other Pi is a DHCP and DNS server, so again is not taxed much at all. What makes the 3b+ run so much warmer than the 3b when idling?

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