I’ve just started work on my ProGrow system after quite a long period of inactivity. Surprisingly, everything on the ProGrow still worked when I first plugged it in after so long. The moisture sensors didn’t seem to accumulate too much corrosion, and everything was still reading properly. It even had the program still loaded. Pretty crazy, considering it’s made using the cheapest parts available, went through a move and has sat idle for 6+ months. The plant that I used to have in the system was very dead. I replaced the soil, added a layer of cat grass seeds and then put an inch of soil over top. I chose cat grass because it’s super cheap, grows like crazy and I have two cats.
I bought a 3V-6V submersible pump from Aliexpress. It cost approximately $2 for one pump! That’s pretty darn cheap. I tested the pump by connecting it directly to a ~6V 18650 battery bank, and it pumped like crazy. It seems to work fine with a 9V battery as well, so I ended up using one of those because I had plenty of spares. I’m going to implement a more permanent rechargeable battery bank soon, possibly with some kind of solar power.
I added a double relay module to the project ( also bought on Aliexpress ), and connected the inputs on the module to digital pins 12 and 13 on the Arduino. It gets 5V and a ground connection from the nearby breadboard that holds the button inputs. A 4 digit segment display was added to the front to display the current sensor readings, instead of sending the information through the serial connection. I bought the display from RobotDyn on Aliexpress ( big surprise ), and it uses the arduino-tm1637-master library. Currently it displays the temperature, air and soil moisture, ambient light, run time and the delay between automatic samples. It also displays the project name and some other stuff while turning on.
I attached a mason jar to the side of the container in order to act as a water reservoir. With some hot glue and double sided tape, I attached the pump to the inside and ran some wires. I attached the pump to a 9V battery, and connected that to the relay that is controlled by pin 12 on the Arduino. I use the values read from the moisture sensors in order to control power to the pump. When the soil moisture falls below a certain threshold for a certain length of time, the pump will engage and water the plant until the average moisture rises back up. I plan to add another sensor to indicate when the water level is low in the reservoir, so that it won’t burn out the pump if there’s no water.
I intend to remove the RGB LED on the side to free up 3 more GPIOs. This will give me extra pins for future use. I am also going to move the relay modules to different pins.
I’m going to try to design and 3D print some customized enclosures for the modules that I have added. When my wireless chips and SD module come in the mail, I am going to implement wireless data logging and communication. I’m also looking into purchasing a sensor expansion board, and some silicon boards to clear up the wiring a bit. Not sure if the name “ProGrow” is going to stay.
I’m also going to try to make more detailed posts about the individual steps at a later date.