The pilot started as a weekend build: a microcontroller, a handful of solenoid valves, and a lot of debugging in a garage that smelled like solder flux for a week.
Today it runs unattended, drawing from the same sensor network the chapter uses for monitoring, and it has freed up hours ambassadors used to spend hand-watering after school.
4
Plots on automated drip lines
~5 hrs/wk
Hand-watering time saved
$150
Total parts cost
“It waters when the soil says to, not when we remember to.”
How the schedule actually decides
Rather than watering on a fixed clock, the controller checks each plot's moisture reading every fifteen minutes and only opens a valve when the reading drops below a threshold the ambassadors set for that crop.
Different crops, different thresholds
Leafy greens and root vegetables don't want the same moisture ceiling, so each plot's valve has its own threshold, tuned over a few weeks of trial and error rather than assumed up front.
Why this matters
Overwatering wastes a scarce resource and can wash out nutrients ambassadors are trying to build up in the soil. Watering on demand, not on a clock, is the whole point.
The build
- 1
Map the plots to valves
Each of the four plots gets its own solenoid valve on a shared drip manifold, so a fault in one line doesn't take down the rest.
- 2
Wire the controller
A single microcontroller switches all four valves and reads moisture data over the same network the sensor project already built.
- 3
Write and test the logic
The scheduling logic went through three rewrites after the first version left a plot flooded overnight on a bug in the threshold check.
- 4
Add a manual override
A physical switch lets ambassadors force a plot on or off, since no one wants to debug code standing in the rain.
| Part | Cost | Purpose |
|---|---|---|
| Solenoid valves (x4) | $60 | One per plot, normally closed |
| Microcontroller | $10 | Runs scheduling logic, shared sensor feed |
| Drip manifold + tubing | $55 | Distributes water to each plot |
| Enclosure + wiring | $25 | Weatherproofing for outdoor mounting |
The team is documenting the build so other chapters can replicate it with parts costing under $150, and is already scoping a second version that adds a weather forecast feed to skip watering ahead of rain.