How to control relay module with BeagleBone Black

I’ve finally received my 5V relay module and started messing up with my BegleBone Black tiny Arm board won from at Confitura conference.

Idea is to build a flowers watering system calculating water amount from current temperature and weather forecast with watering statistics.

Here’s how it works:

So. I’ve first connected my relay module to power(P8_7) and ground(P8_1) connectors on BB and input to some GPIO pins (ex: P9_8, P9_10). My relay module has only 2 relays, but you can connect as many as you like, just use more GPIO pins.
Here you can get nice pinout image to check what pin is where:

Next we have to enable our GPIOs so we can control them:

if [ ! -d /sys/class/gpio/gpio67 ]; then echo 67 > /sys/class/gpio/export; fi

You have to do this as root to have access. Remember that GPIO numbers are different from pin numbers. Check pinout if needed.

Next we can power up our GPIO, it should enable relay channel:

echo out > /sys/class/gpio/gpio68/direction

to disable:

echo in > /sys/class/gpio/gpio68/direction

That’s all. Now you can use your BeagleBone to power on/off almost any device you like. Here’s a full script used in the demo if you like to check it out:


if [ ! -d /sys/class/gpio/$gpio1 ]; then echo $gpio1 > /sys/class/gpio/export; fi
if [ ! -d /sys/class/gpio/$gpio2 ]; then echo $gpio2 > /sys/class/gpio/export; fi

click() {
    state="`cat /sys/class/gpio/gpio$1/direction`"
    if [ $state = "in" ] ; then

    echo $state > /sys/class/gpio/gpio$1/direction

while : ;do
    click $gpio1
    sleep .2
    click $gpio2
    sleep .4
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