I was looking for ways to automate my lawn watering system and make it more efficient. Installing a full smart irrigation system can cost thousands of dollars. As an electronics hobbyist, I decided to take on the challenge of building my own solar-powered smart sprinkler controller for under $100. In this article, I will share how I built an automated sprinkler system using basic electronic components, a microcontroller, and repurposed parts.
Selecting the Components
The first step was selecting the right components for the project within a $100 budget. Here is what I used:
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Microcontroller board - I went with an Arduino Uno which can be purchased for around $20. Arduino is an easy to program open-source electronics platform.
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Water pump - I repurposed an old 12V bilge pump designed for marine use. It had enough power to push water through my system.
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Water storage - I used a 5 gallon plastic bucket to hold water pumped from my main line.
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Tubing & connectors - I used 1/2" PVC tubes with various tees and elbow connectors to route the water.
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Relay - To control the 120VAC power to my pump from the Arduino I used a 5V relay module I bought for $7 online.
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Moisture sensor - To monitor soil moisture I used a simple resistive soil moisture sensor that cost around $5.
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Solar panel - I had a 10W 12V solar panel left over from another project that was enough to power the system.
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Battery - To store power from the solar panel I repurposed an old 12V sealed lead acid battery.
Assembling the Control Circuit
I first wired up the control circuit on a breadboard to test it out. This included connecting the Arduino, moisture sensor, relay module, and other components.
The basic circuit logic was:
- Arduino reads moisture level from sensor
- If moisture below threshold, Arduino triggers relay
- Relay switches power to water pump
- Pump fills water bucket from main line
- Water flows through tubes to sprinklers
I tested the circuit to make sure the pump turned on when the moisture sensor dropped below a calibrated threshold.
Coding the Sprinkler Logic
With the circuit working, I wrote an Arduino program to control the watering schedule.
The program included functions like:
- Read moisture sensor data
- Activate pump relay based on moisture level
- Log watering events to monitor usage
- Only water during allowed days/times
- Adjust watering duration based on moisture reading
I set up a loop to read the moisture sensor and check the clock time. If moisture was low and it was an allowed watering time, it would turn on the pump for a duration proportional to the moisture deficit.
This ensured the lawn only got watered when needed during appropriate times.
Constructing the Enclosure
With the electronics and code ready, I installed the components into a weatherproof enclosure.
I mounted the Arduino, relay module, and soldered connections on a plastic backplate and screwed everything down. I routed the wiring neatly through some strategically drilled holes.
I enclosed the board and battery in a plastic tool box to protect it from the elements. The moisture sensor wires and solar panel cables fed through a tight-fitting grommet.
Finally, I attached the box to a pole mount and secured the solar panel with brackets. I also drove the sensor probes into my lawn and routed PVC tubing to my sprinklers.
Results of My Homemade Smart Sprinkler
After final testing, I was thrilled that my homemade smart sprinkler system worked flawlessly!
The total cost was under $90, way cheaper than an off-the-shelf product. And I gained the satisfaction of building it myself.
My lawn is now watered precisely when needed based on actual moisture data. The solar panel powers the system continuously without any electrical hookup or battery change.
This project showed that with some DIY effort, you can build automated solutions using basic electronics and Arduino programming skills. I'm now looking at adding WiFi control, rain sensing, and other features to expand the functionality even more!
Let me know if you try this or a similar project yourself. I'm happy to answer any questions in the comments below.