One big problem with the GuruPlug is it's high temperature. In the newer versions of the GuruPlug, GlobalScale added a small fan to improve air flow. Here are some temperature measurements taken with improved cooling, modified fan and without fan. The temperature measurements have been taken on the CPU, which is the source of the most heat.

 

Measurement setup

The temperature measurement has been done using a Fluke 179 Multimeter with temperature measurement capability. Wireless and Bluetooth were switched off, no eSata or USB devices were connected. One wired network connection was used to watch the system monitor and start and stop the CPU stress test.

 

Environment temperature: 23.2 °C (73.67°F)

 

The 100% CPU load has been tested using the "stress"-command:

stress -c 5

If "stress" is not available, it can be installed using

sudo apt-get install stress

 

Here is a picture of the measurement setup. Some heat transfer paste was used to improve the measurement. The housing has been closed as good as possible during the measurement.

p1120029_2

 

 

Measurement data

 

Without fan

Starting temperature: 23.2°C (73.67°F)

average CPU load [%] Uptime [min] Load average (htop) Temperature [°C] Temperature [°F]
 2  2  0.25  44.5  112.1
 2  5  0.01 0.12 0.08  52.9  127.2
 2  10  0.00 0.04 0.05  61.5  142.7
 2  15  0.00 0.01 0.02  66.8  152.2
 2  20  0.00 0.00 0.00  70.2  158.4
 100  21  2.43 0.70 0.20  76.8  170.2
 100  22  3.44 1.04 0.38  79.6  175.3
 100  23  4.32 1.70 0.65  82.5  180.5
 2  24  2.29 1.58 0.64  77.0  170.6
 2  25  0.29 1.31 1.29  75.8  168.4

 

I stopped the measurement at 82.5°C (180.5°F) since the temperature was very high already.

 

With modified fan (full speed)

Starting temperature: 35°C (95°F)

The fan location has been modified to ensure better air flow

No resistor to limit the fan speed

average CPU load [%] Uptime [min] Load average (htop) Temperature [°C] Temperature [°F]
2 1 0.68 0.25 0.09 40.6 105.1
2 2 0.25 0.20 0.08 38.7 101.7
2 5 0.01 0.11 0.07 37.9 100.2
100 6 1.97 0.64 0.25 43.6 110.5
100 7 3.79 1.37 0.52 45.2 113.4
100 8 4.50 2.40 0.99 45.8 114.4
100 15 5.15 4.31 2.34 45.9 114.6
2 16 2.72 3.85 2.28 39.3 102.7

 

At 45.9°C (114.6°F), the temperature did not raise much any more so I consider it as the maximum temperature and stopped the measurement.

 

With modified and silent fan (about half speed)

Starting temperature: 35°C (95°F)

The fan location has been modified to ensure better air flow

Resistor (39Ω) used to limit fan speed

average CPU load [%] Uptime [min] Load average (htop) Temperature [°C] Temperature [°F]
2 1 0.84 0.29 0.10 43.2 109.8
2 2 0.33 0.24 0.09 43.9 111.0
2 5 0.06 0.15 0.08 46.3 115.3
2 10 0.00 0.05 0.05 47.3 117.1
100 11 3.29 1.01 0.33 54.8 130.6
100 12 4.31 1.62 0.62 57.1 134.8
100 13 4.75 2.28 0.89 58.2 136.8
100 20 5.04 4.37 2.38 59.8 139.6
100 30 5.15 5.01 3.75 60.0 140.0

 

The maximum temperature can be defined at 60°C (140.0°F) since the temperature did not really raise any more.