An automatic garden watering system was my original goal for my home automation system, especially as this year we have had very sunny and dry conditions. I was out watering my plants nearly every night.

I have several different things I needed to water; raised beds with vegetables, a wall of strawberries, some fruit trees, and we tried our hand at potatoes this year as well.

Four zones fitted nicely with my four channel MOSFET board I had designed. There is a dedicated blog post about the process I went through to design and manufacture the MOSFET shields and you can buy them on Tindie for you own projects. 😊

I designed a water manifold with four 12v solenoids which would give me four individually controlled watering zones and a pass-through connector so I could daisy chain additional controllers later as required.

I needed to split the watering zones up because my water pressure could not drive all the drippers and sprinklers at the some time, if they were all connected in series. You need a reasonable amount of pressure to get the mini sprinklers to work properly and you can’t drive more than 15-20 at once as the pressure drops too low.

I used Hoselock Easy Drip system to supply water to the plants and beds I needed to water. The system is simple to configure. You run a standard hose around the bed, and clip on sprinkler heads which pierce the hose and provide irrigation. There is also a micro drip system which uses smaller 4mm hose for pots. I used the Easy Drip for all the beds and Micro Drip for the strawberries.

Design

I built the manifold out of ¾” threaded pipe connectors and 12v solenoids. Next time, I might try making the manifold from soldered fittings, but the threaded fittings gave me the flexibility to change the design as I built it. I have also found some ready-made manifolds since building mine, so I might try those too next time.

I built a wooden box out of some old decking boards I had, so I could mount the manifold and controller on the fence.

The device would be in my garden, so I used a Wemos D1 Mini microcontroller with an external antenna to give me a bit of extra WiFi range. It will be powered by a 12v battery, so I mounted the Wemos and MOSFET shield in an IP60 weatherproof case, with a DC-DC step down convertor to give me 5v to power the Wemos and 12v from the battery for the solenoids.

The plan is to charge the battery from a small solar panel, so its completely wireless in the garden. The current draw is tiny. The solenoids only draw about 600mA each and they are only on for short amounts of time. Even without a solar panel to charge the battery, it would last maybe 2 weeks between charges.

The main water feed from the garden tap comes in on the right hand side via a manual valve so I can quickly turn off the water if I need to, without having to walk all the way back down the garden. I leave this on and connected all the time, so the watering system can water at any time of the day or night.

There are four watering zones, one on each solenoid. The four zones are;

1. Potatoes
2. Vegetables Beds
3. Fruit trees
4. Strawberry Wall

The last connection on the left is a pass through from the main feed, also via a manual valve, where I can either daisy chain another four zone controller, or attach a hose and hand held sprinkler for manual watering.

Testing

To test the controllers and manifold worked correctly before I installed it permanently, I wrote a simple script that turned on each channel sequentially, with an MQTT message, every 2 seconds.

I positioned the controller with its external antenna just on the edge of my house WiFi range, so it was as far up the garden as it could be, but still in range.

The automation is driven by NodeRed. I water each zone for 20 mins every morning at 6am. I can add more logic later if I need. There are all kinds of modules and sensors I could add to measure soil moisture or rain sensors and decide not to water if its been raining or the ground is already moist, but there’s no risk of over-watering anything at the moment, so it just waters every day for 20 mins.

In theory if the summer gets really hot, I could measure soil moisture and decide to add an extra watering cycle midday if the ground is really drying out in the sun. But that will be a phase two.

I also have a manual override using the NodeRed dashboard buttons, so I can manually turn zones on and off from my mobile phone.

The results have been amazing. The strawberries have really benefited for daily watering. We got a fantastic crop of potatoes too. Now the automatic watering system is in place we will increase the volume of plants next summer, now I’m confident they will all survive, and I don’t need to spend hours watering them every day! 😊