Disclaimer:<\/strong> The project:<\/strong> On the first machine we set up then machine seemed to be running Owncloud stable at 49 – 50 C on the CPU, but on 2nd day we noticed it going to 75 C and everything went very slow due to CPU core shut downs. Reason for the spike is known, generation of Previews on images was turned on. Even if turning that feature off which we did then there will always come peek times where the CPU needs to\u00a0be able to take load. This guide also applies for other Orange PI projects, basically if you are doing something that needs CPU load then the CPU on Orange PI will heat up really fast. Of course we already had heat sinks on the CPU and memory chips so it was clear that fans would be needed to ensure stability and performance.<\/p>\n Fans are loud! 1.<\/strong> GPIO controlled fan. (We will be taking 3 GPIO pins for this though a slightly more complex\u00a0circuiut can do 3 speeds with just 2 GPIO pins) So in short if the plan works then the Fan is supposed to be silent 99% of the time<\/strong>.<\/p>\n The circuit: Selecting the components: In the end we took 5V fan, that takes 200 mA and is 5 x 5 cm<\/strong>.<\/p>\n We thought we would be using resistors for R4 and R5 with higher values so were concerned about the wattage on them but the fan does not run at lower voltage than 3,6 V at all. So doing the math on R4 and R5:<\/p>\n R4 and R5 values were selected based on what gave good speeds on the fan in actual tests, 8.2 Ohm drops the voltage on the fan to about 3,6 V (measured with multimeter) Then to verify the wattage for them:<\/p>\n Original fan voltage: 5V<\/p>\n Original fan current: 0.2A<\/p>\n V=IR (Ohm’s Law), so 5 = 0.2R \u00a0 => \u00a0 R = 5 \/ 0.2 \u00a0 = \u00a0 25<\/p>\n Fan resistance: 25 \u03a9<\/em><\/p>\n Target voltage: 3.6V<\/p>\n V=IR (Ohm’s Law), so 3.6 = 25I\u00a0\u00a0 =>\u00a0\u00a0 I = 3.6 \/ 25 \u00a0 =\u00a0 0.144<\/p>\n Target current: 0.144A<\/p>\n Voltage drop across resistor: 5V – 3.6V\u00a0 =\u00a0 1.4V<\/p>\n V=IR (Ohm’s Law), so 1.4 = 0.144R\u00a0\u00a0\u00a0 =>\u00a0\u00a0\u00a0 R = 1.4 \/ 0.144 \u00a0\u00a0 =\u00a0 9.722<\/p>\n Target resistance:\u00a0 9.722 \u03a9<\/em><\/p>\n Power dissipated by resistor:\u00a0 1.4V * 0.144A\u00a0 =\u00a0 0.202W<\/p>\n<\/blockquote>\n The actual power dispatched is a little less than shown in the math above as\u00a0going through the transistor does not deliver 5V, So in the end 1\/4 W resistors were enough.<\/strong><\/p>\n The hunt for transistor that would be able to take this amount of current and possible spikes started and we in the end decided on BC-337-25 (note the 25 variation) which is NPN transistor and has current rating of 0.8 A in the collector.<\/p>\n For the current then we need to apply the following formula: I(B) = I(C) \/\u00a0\u03b2. \u00a0(The\u00a0\u03b2 will usually be marked as hfc in the transistors specs)\u00a0You google the spec for your transistor and find the Beta Value, it will have some range depending on current, it will be marked as On characteristics in the spec. Mine has the \u03b2 spec of 160 to 400 at 100 mA.\u00a0Since we are using 200 mA then we will choose\u00a0\u03b2 of 250. Now that we have the voltage and current then R1, R2 and R3 = 2,6 \/ 0,0008 A =\u00a03250\u00a0\u03a9\u00a0<\/em>\u00a0<\/em>(2,6 since \u00a0base of the transistor wants 0.7 V)<\/em><\/p>\n Manual tweaking of the speed on the fan controller ended us then with 3,6k\u03a9 on R1 and R3 and 4,7 k\u03a9 on R2.<\/em><\/strong><\/p>\n After tweaking and testing it on the breadboard for a while then it was time to put the circuit on final board:<\/strong><\/p>\n Measured final values were:<\/p>\n
\nWe do not take any responsibility for possible errors in the guide or errors that you might do wiring it up. Incorrect wiring can result in damaged sensor or damaged Raspberry PI.<\/p>\n
\nThis started out as project where me and a guy name H\u00f6r\u00f0ur Kristj\u00e1nson (he is a great developer) were building Owncloud servers from cheap Orange PI PC machines. This guide will not handle installing or setting up the Owncloud, but more of dealing with heat problems that we encountered.<\/p>\n
\n<\/strong>Loud fans was not exactly something that we were prepared to swallow as those servers are being built as home servers where they need to be quiet. So after some thinking and discussion then this plan was made:<\/p>\n
\n2.<\/strong> C++\u00a0daemon\u00a0would be written that reads the CPU temp and turns on the fan, Slow at 60 C, faster at 65 C and full speed at 70 C.
\n3.<\/strong> Cut hole in the top of the boxes for the fan, and 3D print fan brackets that will also store the fan controller circuit. (We do not have the same Orange PI PC cases so we will try to make our fan bracket generic so it can work on both cases)<\/em><\/p>\n
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\n<\/strong>This is the circuit we came up with:<\/p>\n![\"FanControllerCircuitScheme\"](\"https:\/\/i0.wp.com\/einhugur.com\/blog\/wp-content\/uploads\/2016\/04\/FanControllerCircuitScheme.png?ssl=1\")
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\n<\/strong>When looking for fans that are 5V and suitable for the task then it soon was clear that fan would take from about 145 mA to 200 mA.<\/p>\n\n
\nWhich means I(B) will be: 0,2 \/ 250\u00a0=\u00a00,0008 A\u00a0(This is how little we will be taking from the GPIO pin)<\/p>\n
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