This is a funny project that makes our plants “talk” to us. It’s very simple and you can create it in few hours. We use a sensor to read the soil moisture of our plant and a led matrix to dislay how the plant “feel”. You can use an ATtiny85 as a microcontroller.

Step 1: Order Materials

Step 2: Wiring Instructions

To wire your ATtiny85 to your Sensor and the MAX7219, connect the following pins:

ATtiny85 Pin1 –> NC
ATtiny85 Pin2 –> Sensor A0 (Analog out)
ATtiny85 Pin3 –> NC
ATtiny85 Pin4 –> GND
ATtiny85 Pin5 –> MAX7219 DIN
ATtiny85 Pin6 –> MAX7219 CS
ATtiny85 Pin7 –> MAX7219 CLK
ATtiny85 Pin8 –> +5V

L78L05 Pin1 –> Output +5V
L78L05 Pin2 –> GND
L78L05 Pin3 –> Input from battery +9V

Don’t forget to connect all the GND together (Sensor, Attiny85, MAX7219). We suggest to connect and the two capacitors to your L78L05 (see the image on the right).

Step 3: Prepare the ATtiny

To program your microcontroller (ATtiny85) you will need an Arduino Uno or a Tiny AVR Programmer.

If you choose an Arduino Uno to program the ATtiny follow the steps below:

Connect the Arduino to the ATtiny as follows:

ATtiny85 Pin 8 – Arduino +5V
ATtiny85 Pin 4 – Arduino Ground
ATtiny85 Pin 1 – Arduino Pin 10
ATtiny85 Pin 5 – Arduino Pin 11
ATtiny85 Pin 6 – Arduino Pin 12
ATtiny85 Pin 7 – Arduino Pin 13

Electrolytic Capacitor 10uF GND – RST

If you haven’t already, download the Arduino software, version 1.0.4 (1.0.3 and 1.0.1 should work too, but not 1.0.2). Install the Arduino software, following the instructions for Windows or for Mac OS X.
Download the ATiny master.zip file.
Unzip the attiny master.zip file. It should contain an “attiny-master” folder that contains an “attiny” folder.
Locate your Arduino sketchbook folder (you can find its location in the preferences dialog in the Arduino software)
Create a new sub-folder called “hardware” in the sketchbook folder, if it doesn’t exist already.
Copy the “attiny” folder (not the attiny-master folder) from the unzipped ATtiny master.zip to the “hardware” folder. You should end up with folder structure like Documents > Arduino > hardware > attiny that contains the file boards.txt and another folder calledvariants.
Restart the Arduino development environment.
You should see ATtiny entries in the Tools > Board menu.

Next, we can use the Arduino as an ISP to upload a program to the ATtiny:

Upload to the Arduino the ArduinoISP from "File - Examples", now you are ready to program the ATtiny.
Download the Arduino code for your project and upload it to your ATtiny85