A plant friendly, attiny85 based AVR project that waters plants while you're away! Controls two 12v water pumps, running them for a pre-configured duration every 24h.
- Event driven architecture
- Priority scheduling
- Minimal part count
- Low power mode to minimise current draw
- Durable configuration storage (in EEPROM)
- Watchdog timer waking drastically reduces power for long sleeps
- Sampling-based (software) button debouncing
Hold down the one (and only!) button to start the pump; hold it as long as needed to water the plant, and release! The system remembers how long the pump ran for, and runs it again in 24.
If you want to run a pump test, press the button and release it within 1 second and the pumps will run for the configured duration.
Overflow detection uses a simple pair of wires in a saucer under the plant. If there's (sufficient) water in the saucer, it conducts the current between the detector wires and prevents the pumps from turning on. Simple but effective!
Detection is implemented per-pump, and is evaluated each prior to the respective pump being activated. This allows water to build up during pumping, but prevents further pumping until the water level has reduced.
The firmware is implemented as an event-driven finite state machine, entering low-power sleep until an event (button pin change or watchdog timer interrupt) wakes the MCU.
Priority is always given to button events over the watering timer.
Ensure the button is not pressed, and neither overflow wire is connected.
Run make flash and for the first use of the MCU, make flash too.
flowchart TD
_s[Sleep]
S[Enable Interrupts]
S --> _s
_s --> |Interrupt Fires| Handle[Set Event Flag]
Handle --> |Main Loop|Main{Evaluate Events}
Main --> |Button|DisablePump1[Pump Off]
DisablePump1 --> DebounceButton[Debounce]
DebounceButton --> |Measure Time Pressed|MeasureTime{More Than 1 Second?}
MeasureTime --> |>= 1 Second: Train|Train[Pump On]
Train --> |Release Button|TrainOff[Pump Off]
TrainOff --> Store[Store Pump Duration in EEPROM]
MeasureTime --> |< 1 Second: Test|Test[Test Pump Run]
Test --> PumpOn
Store --> S
Main --> |WDT|D[Watchdog Time Trigger]
D --> |Time to Start|PumpOn[Pump On]
PumpOn --> |Watchdog Sleep for EEPROM Duration|S
D --> |Time to Stop|PumpOff[Pump Off]
PumpOff --> S