Banana Pi BPI-R3: Everything you need to know

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Part 4: Installing a Fan-Cooled Heat Sink

The Banana Pi R3 comes with three onboard connectors, as shown in the photo below. You got two FAN PH2.0 (2PINS + 4PINS) connectors. an Input 12V power DC input source (VH3.96 2PINS) and third XH2.54 4PIN SATA power connector that can be used to power a 12V FAN.

FAN Wiring Configurations (Options)

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Configuration Option No. 1 (Passive Cooling)

If you don’t need the cooling fan option, you can order the following Heatsink from AliExpress and cut 20 mm from the 100 mm length. If 60 mm is too long, you will need to cut 3 mm of material using a circular saw. A Heatsink with dimensions of 80x57x10 should fit well and cover most of the R3 board components (Chips).

Cooled FAN Heatsink

This part might be a bit tricky. Because there is currently no official Heatsink with a built-in FAN that is fully compatible with the R3 board, and this Heatsink Cooling Fan is designed to fit into a video card, you will have to buy a suitable four or two pin type and replace the wire connector of the FAN with an XH2.54-4P / VH3.96 connector. This can be done by crimping, or the fastest method, in our opinion, is buying a pre-made cable with a connector included and soldering the wires together.

Preparing Conductive Silicone Thermal Pad

Based on the size of the chips, you can use scissors and cut the necessary width and height for the pads. Remember that the Heatsink’s 55 mm length is slightly smaller, so it will not fully cover most chips on the R3 board. It will comprehensively cover the 2GB DDR4 and the MediaTek MT7986A SoC Chip.

Cutting Conductive Silicone Thermal Pad

There are better solutions than this option, but it’s better than nothing. Plus, it’s fast, and you also have four mounting screws, which provide reasonable clamping force against the chips, helping to improve heat convection more effectively.

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Configuration Option No. 2

Using the CN34 (XH2.54-4PIN) Connector as the fan 5V/12V power source.

Connecting 4 Pins Cooled Heatsink wires w/ the XH2.54 4 PIN wires

XH2.54-4PIN Color	FAN Wire Color
White	Black
Yellow	Yellow
Black	No need to connect
Red	No need to connect

Final Step (Powering/Operating the FAN)

To check that everything is working and to power the FAN on using the GPIO Interface controller, you will need to execute the following commands:

echo 419 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio419/direction
echo 1 > /sys/class/gpio/gpio419/value

Option #1

You don’t want to turn the FAN on constantly. You can also create a script to time the FAN operation when reaching a specific temperature. For example, when the CPU temperature is above 45 °C, as shown below, the Fan starts to power for 30 seconds.

Fan Control bash script:

#!/bin/sh

pin_num=8
sleep_time=5 #seconds
fan_time=30 #seconds
fan_temp_threshold=45

gpio_num=$((pin_num + 411))
echo $gpio_num > /sys/class/gpio/export
gpio_sys_path='/sys/class/gpio/gpio'
gpio_sys_path="${gpio_sys_path}${gpio_num}"
current_dir="`cat ${gpio_sys_path}/direction`"
if [ "$current_dir" = "in" ]; then
	echo out > "${gpio_sys_path}"/direction
fi
echo 0 > ${gpio_sys_path}/value
while [ true ]
do
temp=$((`cat /sys/class/thermal/thermal_zone0/temp`/1000))
if [ "$temp" -gt "$fan_temp_threshold" ]; then
	echo 1 > ${gpio_sys_path}/value
	sleep $fan_time
	echo 0 > ${gpio_sys_path}/value
else
	sleep $sleep_time
fi
done

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How to Automatically load the script

If you have already created the script file Fan.sh under /etc/init.d/ you will need to follow these steps:

• Step #1: Invoke the “enable” command to run the init script on boot: /etc/init.d/Fan.sh enable
• Step #2: Now, the script will automatically run on boot. You can check to make sure it’s running in the background by issuing the command: top

#!/bin/sh /etc/rc.common

pin_num=8
sleep_time=5 #seconds
fan_time=30 #seconds
fan_temp_threshold=45

gpio_num=$((pin_num + 411))
echo $gpio_num > /sys/class/gpio/export
gpio_sys_path='/sys/class/gpio/gpio'
gpio_sys_path="${gpio_sys_path}${gpio_num}"
current_dir="`cat ${gpio_sys_path}/direction`"
if [ "$current_dir" = "in" ]; then
	echo out > "${gpio_sys_path}"/direction
fi
echo 0 > ${gpio_sys_path}/value
while [ true ]
do
temp=$((`cat /sys/class/thermal/thermal_zone0/temp`/1000))
if [ "$temp" -gt "$fan_temp_threshold" ]; then
	echo 1 > ${gpio_sys_path}/value
	sleep $fan_time
	echo 0 > ${gpio_sys_path}/value
else
	sleep $sleep_time
fi
done

Option #2

To automatically control the speed of your fan base on Pulse-width modulation (PWM), you can install the Module and script according to the following steps:

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Configuration Option No. 3

Using the CN22 (PH-2PIN) Connector as the fan 12V constant power source.

Connecting 4 Pins Cooled Heatsink wires w/ the VH3.96-2PIN wires

For a constant (Always on) 12V power source, you can use the VH3.96-2PIN DC input connector. We tested it, and it worked fine for us.

VH3.96-2PIN Wire Color	FAN Wire Color
Black	Black
Red	Yellow

Configuration Option No. 3 (With Support for PWM)

This wiring should work only with a 5V Fan with 3 or 4 wires, as it has a separate PWM wire colored in blue. We tried to power a 12V FAN, but we were unsuccessful. The FAN started working every few seconds and stopped, and vice versa. If the FAN spinning is correlated with the thermal sensor operation, it’s an annoying configuration we prefer to avoid.

Instead of using the 5V power source, If you order the Heatsink with the 12V Fan included, you should get the necessary “full” voltage from the XH2.54-4PIN SATA connector or the DC IN 12V VH3.96 connector.

Configuration Option No. 4 (Without PWM Support)

Connecting the 3-pin cooled heat sink wires with the XH2.54-3PIN wires is the simplest installation option. Just plug the fan power into the 5V 3PIN power socket and enjoy the added convenience of setting a maximum temperature threshold. Once this threshold is reached, the fan will automatically start spinning, ensuring effective heat dissipation.

Adjusting these trip points

These trip points are predefined temperature values at which the system triggers certain actions, such as adjusting fan speeds or activating cooling mechanisms, to prevent overheating and maintain safe operating temperatures.

Specifically, trips are numbered. For example, a “trip_point_4_temp” indicates the fourth thermal trip point temperature for the system. When the temperature sensor in the system detects that the temperature has reached or exceeded this specified trip point temperature, it triggers a response, such as increasing fan speed, to help cool down the system and prevent damage from excessive heat.

By setting and adjusting these trip points, users can customize how their system responds to temperature changes, ensuring optimal performance and preventing overheating issues.

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Controlling the fan rotation speeds:

• You can essentially set a temperature threshold (in this case, 70000) at which the fan will adjust its speed.

echo 70000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp

To lower the fan rotation speed, you can increase the temperature value in the command. For example, to make the fan rotate slower, you can set a higher temperature threshold. Here’s an example:

You can change the command to: echo 80000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp

By increasing the temperature threshold to 80000, the fan will trigger at a higher temperature, causing it to rotate at a lower speed compared to when it was set at 70000. This adjustment can help regulate the fan’s rotation speed based on your system’s temperature needs.

In this example, we have set the tipping point temperature to be 50 °C. Once the CPU temperature reaches this temperature, the fan will automatically start spinning. Considering the temperature inside the case is high, especially in a closed case, the temp will be equal or exceed this threshold, therefore our fan to continuously spin.

echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp
echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_3_temp
echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_2_temp
echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_1_temp

Setting the trip points to load automatically when the OpenWrt OS boots is simple. You can copy and paste the command above into the Local Startup tab accessible under System -> Startup as shown in the photo below.