• First we have to calibrate the moisture sensor with the arduino UNO and the file CalibrateMoistureSensor/src/main.cpp. To do this, we connect the sensor as shown below:

• After the sensor is calibrated, we can program the ATtiny with the attiny_plantmonitor/src/main.cpp file.
• In this project we work with the tinysnore library to put the ATtiny into deep sleep, which increases the life of the button cell battery.
• We also use the TimerFreeTone library for the buzzing sound.
• In the readMoistureSensor() function, we get the moisture value from the sensor and map it into percentage values according to the values we got from calibrating the sensor.
• If the percentage is less than 10, the moisture value is set to true for the alarm.
• In the function flashLED(bool withSound) we turn the LED on and off, and if the bool "withSound" is true, we also turn the buzzer on and off.
• The function readPhotoresistor() evaluates the brightness. If the brightness becomes less than 400, the bool "dark" becomes true.
• In the loop we read the photoresistor and the moisture sensor.
• We check if the bool "dark" is true and the "moistureThreshold" is true, then the alarm is without buzzer.
• If "dark" bool is false and "moistureThreshold" is true, the alarm is with buzzer.
• At the end we send the ATtiny into deep sleep (for test purposes only for 10 seconds at first, if it works properly you can increase the ms here).

• This DIY moisture controller for plants runs on an ATtiny 25.
• We have built in a capacitive soil moisture sensor to measure the moisture of the plant.
• For the alarm sound we have built in a piezo buzzer and a 100 Ω resistor to soften the sound.
• We also built in a 3mm LED connected to a 100 Ω resistor.
• To switch between the alarm with the sound or the LED, we have built in a photoresistor connected to a 10k Ω resistor.
• The moisture control is powered by a CR2032 3V button cell battery.

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