I always wanted to have my small garden on balcony, but hot summer, my lazyness and lack of knowledge about gardening whatsoever were reasons why I didn't have proper one. My wife is better in that part, but lack of time drove her off that garden.
So I decided to make my own watering system. It's isn't much for now, for one (bigger) pot, but it will expand later. This easy, small system is made of one Arduino Nano (clone, I guess, having in mind the price), one 3.3v relay, 12v self-priming pump, soil humidity sensor, two power supplies (5V for Nano and 12V for pump) and bunch of wires and hoses. And 25 liter canister.
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Step 1: Setting Up - Hardware
Hardware is set-up is straightforward, no "extras". Soil humidity sensor output is connected to Nano A3 pin, as it reads analog level (in this setup I don't have use of digital 0/1 input), and to 5V and ground pins. Relay is connected to D5 pin, 3.3V and ground pins. 12V power supply is connected with one wire straight to pump, and other wire is connected to relay (to COM output pin). From relay, NO pin (as I don't want pump to work if for some reason power on Nano fails) wire is connected to other pump pin.
Step 2: Setting Up - Software
All my Arduino projects are made with Visuino, as I find it easy, yet powerfull IDE to work with.
Visuino sketch is easy, it reads analog value from A3 pin to MapRange component, to switch it to percentage. From that component iI have two CompareAnalogValue components, one for startiong the pump, other for stoping it. If value from soil humidity sensor is equal or below 50, it will send impulse to FALSE value of DigitalToggleSwitch, which is connected to D5 pin output. Other CompareAnalogValue conponent looks for value higher than 50 and sends impulse to TRUEvalue of DiggitalToggleSwitch. This seems little bit awkward, but it is necessary for relay to work properly (TRUE sends HIGH signal to relay, and then relay is switched to NC; FALSE sends LOW to relay, and then relay is switched to NO).
Visuino scheme is attached.
Step 3: Setting Up - Rest
Hoses are set up in place, the one on peppers is punctured on several places and sealed on the end, and everything is connected. Testing was made on almost fully dry soil, and it immediately watered poor peppers (that was intentionally made, of course, for this project ;-) ).
Nano is encased id Minions Tic Tac box, pump and relay attached to it. This set up will be expanded with one more pump and sensor, and it will have only one power supply - I'll put DC-DC step down module, so it will need only one 12V 5A power supply (current set up has one 12V 2A and one 5V 0.5A). Expansion is needed for basil pot, as that plant also needs a lot of water, just like peppers :-)