# Thermal comparison of three embedded Linux boards

Andrew Back
Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.

December 28, 2015 11:32

Thought I'd mention Seek Thermal as a great and budget-friendly alternative to Flir. They have iPhone and Android versions as well as a new standalone version. The iPhone/Android one is cheaper than the Flir One and higher resolution. The software isn't quite as nice maybe, but gets the job done.

I don't know if links are allowed here, so I won't link it (not spam and I'm not affiliated with Seek Thermal, just an owner/user).

May 19, 2015 12:01

@dsearfoss:
If you pass a constant current through a resistor, you will produce a voltage across it. An electric potential difference between the two ends.
As I said, a thrmal circuit is LIKE an electric circuit. If you generate a constant heat (in Watts) in a device with a constant Thermal resistance (not expanding, etc) you will produce a thermal difference between the inside junction (silicon to case) and the outside junction (case to air).
You use this principle every time you add a heatsink: the "case to air" resistance, quoted in degrees C per watt, is lowered. A given number of watts produce a smaller temperature rise. The actual number of Watts PRODUCED remains a function of device voltage and current.
Hence the need to measure voltage and current draw under load, as well as temperature.

May 18, 2015 14:19

"Thermal circuits are like electric circuits - but the current is heat, and voltage is temperature." Sorry but wrong Heat is energy .. The combination of Current and Voltage is energy measured in watts can be converted to BTU's. if current or voltage is zero no energy used no work done you need both . Temperature is the result of work done in the environment it is in

May 18, 2015 12:32

SA_Penguin wrote:
> Thermal circuits are like electric circuits - but the current is heat, and voltage
> is temperature.
> Adding a simple heatsink lowers thermal resistance, so a given amount of heat creates
> a lower temperature difference.
> So the best thing to in a test like this is : add a current meter to the power supply
> line. That gives you actual power being dissated, in watts.
>
> The thermal images just tell you the best places to add heatsinks.

Great comment

May 18, 2015 11:11

Its interesting to note that at the distance the images have been taken, the visual part and the thermal parts of the image combined by their MSX technology are not well aligned. If you look at the images, the hot areas are actually above the location of any components. In the case of the Pi1 Idle the hottest areas are shown on the FLIR as being the Ethernet connector and the bottom of the HDMI socket. Using a different thermal imager (in this case a Land Instruments ARC) with just a pure thermal image, its easier to see that the hot spot are actually the Ethernet PHY and the power regulator.
[attachment=0:1x7azate]pithermal.png[/attachment:1x7azate]

May 18, 2015 10:47

Thermal circuits are like electric circuits - but the current is heat, and voltage is temperature.
Adding a simple heatsink lowers thermal resistance, so a given amount of heat creates a lower temperature difference.
So the best thing to in a test like this is : add a current meter to the power supply line. That gives you actual power being dissated, in watts.

The thermal images just tell you the best places to add heatsinks.