Categories
Dev Horticulture

Irrigation Control and Monitoring

The objective of this project is to create a cheaper alternative to commercial irrigation control solutions with added functionality.

Current project objectives:
  • Solar Powered
  • Weather Proof
  • Logging to online database
  • Soil Temperature Monitoring
  • Soil Moisture Monitoring
  • WiFi
  • DC Pulse Latching Solenoid Control
  • Intelligent Watering

I have chosen to prototype the device using the Arduino platform  but any microcontroller with sufficient inputs and outputs could be substituted.

Prototype Hardware List:
Custom DC Pulse Latching Solenoid Controller:

I had an EE look over the schematic for good measure. He told me it was over engineered for what I wanted to do but there are definitely worse things that could have been “wrong” with it. This circuit is used to control 12vdc pulse latching solenoids. Pulse latching solenoids use magnets to latch open or closed making them great for low power projects. The downside to these solenoids is that they require polarity switching to latch or unlatch. The original circuit I based my design off of can be found at rayshobby.net. His circuit is designed for 24vdc latching solenoids and uses an H-Bridge to control polarity. His design is slightly cheaper and smaller but much more complicated and “over engineered.”

tldr; This is the circuit that will allow a microcontroller to control an irrigation setup. This circuit is specifically designed to use Hunter 9-12vdc Latching Solenoids.
I’d also like to mention that the company Hunter is not friendly to work with. They refused to share any information about their latching solenoids telling me only that they were designed to work with “their controllers.” If this circuit doesn’t work as planned I will buy one of their controllers and reverse it including updates to the above schematic. The parts for my circuit design cost around $25 if you go with really nice stuff but could be done for a lot less. I will attach the EagleCAD files soon.

Update (Tuesday, December 16, 2014 at 12:31am PST): This project had to be tabled several months ago to meet both my work and school obligations but I was able to so far get the device logging both temperature and e.c. data to an online database over WiFi in the garden using the LiPoly Battery. I have however as of writing this resumed working on it and plan to finish this project over the course of the next few months. I also broke down and bought a Hunter NODE-100 controller since I could not complete the project in time for the start of the season. The controller has a watering cycle interrupt circuit that I may decide to use instead of the custom controller to not let the device go to waste. The rest of the project however will continue as planned.

Update (Thursday, December 16, 2016 at 1:52am PST): (laughably) I still haven’t finished due to school obligations and various distractions but definitely will this summer (I hope). I will design a new board to interrupt the Hunter NODE-100 that’s currently installed. I’ll probably also swap the Fio for an esp8266 or comparable board. I want to also expand the project to include a board for low power, low cost, solar powered sensor mesh networks.

Update (Tuesday, July 18, 2017 at 3:34am PST): I decided to take this project in a different direction and have chosen to use digital soil moisture tensiometers instead of EC to determine when to water. I am hoping to have boards made by the end of the summer. I’ll make a new post about it as soon as I nail down the feature set.