Watering Control System based on a WRAP for my Balcony Plants


This describes an automatic watering system for my balcony plants based on Gardena micro dripping system. Water comes from a 300l barrel and is pumped to the distribution tubes by a submersion pump. The water is filtered and pressure regulated by Gardena "base units". Watering is controlled by a small computer running Linux which is connected to the internet via WLAN.

In the current configuration watering is done in a simple timer scheme. Later it is planned to take into account precipitation and evaporation both aqcuired from reliable meteorological sources in the internet.

Balcony plants

The balcony plants

More balcony plants and the water tank

More balcony plants and the water tank

Water tank and submersible pump

Water tank and submersible pump

The control valves

The control valves, modified simple watering control timers from Bosch. Only the latching valves and the driver elctronics are used, the timer microcontroller is disabled. Originally the watering timers seem to be manufactored by Claber.

Drawing of the electronic circuit of the watering timer with my modifications.

Alternatively there are affordable solenoid valves from Hunter, e.g. PGV-100-GB

Controlled by a WRAP

All is controlled by a WRAP from pcengines and connected to the internet via WLAN.

Weather protection

Electronics are weather protected by a simple plastic storage box.

LPC connector interfaces to an optoisolator board

The LPC connector of the WRAP interfaces to a optoisolator board.

The LPC connector of the WRAP

The LPC connector of the WRAP carries 6 signals of the SC1100 Geode single chip x86 computer which can be configured as general purpose I/O (GPIO). These control the pump and the valves.

I made up an optoisolator board to protect the GPIO pins from interference. The schematic drawing of the board can be seen here.

On the WRAP runs a Linux fli4l 3.1.2. To configure the GPIO lines and to drive them I have witten some simple programs:

This is the crontab controlling the watering times:

# switch on pump and valves 1 and 2
0 9,16 * * *  gpc_clear; gpc 0 1; gpc_pulse 1; gpc_pulse 3
# switch off valve 1 after 3 minutes
3 9,16 * * *  gpc_pulse 2
# switch off water pump and valves after 5 minutes
5,10,15,20,25,30,35,40,45,50,55 * * * *  gpc_pulse 2; gpc_pulse 4; gpc_clear

fli4l has e3 as editor which has a vi-emulation mode when called as e3vi.
To modifiy the crontab (until next reboot) edit:

e3vi /var/spool/cron/crontabs/root

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