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What are the main sources of heat on the board?

What temperatures do these components reach under load?

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1 Answer 1

up vote 31 down vote accepted

HackADay posted a link to an article (in Spanish - translated to English) with some thermal images, I'll summarise it:

There are three main sources of heat -

  1. The input voltage regulator (bottom left).

    This regulates the input down from Vcc to 5V. Assuming this is a linear regulator, power dissipation will equal P=(Vcc-5)*I, where I is the current usage of the device.

    If you supply the board with 6V, and draw 0.5A, the power dissipated by this chip will be (6-5)*0.5 = 0.5W.

  2. SoC BCM2835 (middle). This contains the ARM11 CPU, GPU and RAM.

  3. LAN951 (right). This is the USB/Ethernet controller.

The following tests were performed at an ambient temperature of 26-27°C with no draft.

Idle - no Ethernet:

Thermal image at idle

  1. 49.9°C
  2. 48.7°C
  3. 53.0°C

Idle - Ethernet connected:

Thermal image at idle with Ethernet

  1. Ethernet controller temp increases to 55.7°C with a maximum of 59.5°C.

CPU Stress Test:

Thermal image with CPU Stress Test

  1. CPU temp increases to 55.7°C with a maximum of 57.9°C.

High Definition Video Playback:

Thermal image with HD video playback and Ethernet

  1. CPU/GPU temp increases to 56.1°C with a maximum of 58.6°C.
  2. Ethernet controller temp increases to 60.8°C with a maximum of 65.1°C.

Conclusion

From the above tests we can conclude that the hottest component is the Ethernet/USB controller, with a maximum of ~65°C (37°C above ambient). The CPU/GPU reaches ~59°C (31°C above ambient), whilst the voltage regulator reaches ~59°C (31°C above ambient).

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It was someone's crazy idea to use a linear regulator, if indeed one is used. These days switchers are tiny and cheap... –  Kuba Ober Mar 2 '13 at 13:45

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