Introduction: Build a Plant Sound Interface With ESP32 and CJMCU-6701

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Building something that can take tiny electrical pulses and turn them into audio is something I've heard of but never researched. With this competition, I thought it would be the perfect time to make something that reads the micro voltage from a plant and turns it into a kind of audio pitch. I already had a big speaker laying around, so I thought, why not?

Supplies

Tools needed for this include the following:

Soldering Iron: Used to solder IO pins onto the microcontrollers and to splice and connect wires.

Computer: Must be able to use the Arduino IDE and connect to the ESP32.

Supplies needed include the following:

Speaker: These will work, but if you want a bigger one, you can use the second linked one.

ESP32: The main controller that processes the sensor data and controls sound output.

CJMCU GSR Sensor: Detects tiny electrical signals from the plant, similar to a biofeedback sensor.

ADS1115 16-bit ADC Module: Converts the weak analog signal from the GSR sensor into clear digital data for the ESP32.

100W Audio Amplifier: Boosts the ESP32’s audio output to drive the speaker.

Speaker: Converts the amplified signal into audible sound. You can use a small one or a large speaker for more impact.

Wires (M-M, M-F, F-F): For connecting all the modules and signal paths.

EKG Pads / Electrodes: Attach to the plant leaves or stems to pick up electrical signals.

10v power supply: Used for powering the amplifier.

Step 1: Solder the IO Pins That Come With the Microcontroller

  1. Grab both of your microcontrollers and the IO pins that come with them.
  2. Align the pins, then solder them.

Step 2: Prepare the CJMCU Sensor

  1. Grab the CJMCU-6701 and the EKG sensor wires.
  2. Solder your wires from the EKG sensor onto the back of the CJMCU on the pads labeled GSR.
  3. My sensors had red and black wires, but the order doesn’t matter.
  4. Make sure your solder joints are shiny and not connected.

Step 3: Wire the CJMCU to the ESP32

  1. Grab both microcontrollers.
  2. Connect 5V on the CJMCU to 3V3 on the ESP32.
  3. Connect the GND of both together.

Step 4: Wire the CJMCU to the ADS1115

  1. Grab the two microcontrollers.
  2. Attach the OUT from the CJMCU to A0 on the ADS1115.

Step 5: Put Together the Amplifier

  1. Follow the instructions on how to assemble it. When you’re done, it should look like this.

Step 6: Get a Headphone Jack

In this, I used an old pair of headphones—but that’s the hard way since you have to figure out which wire is signal and which is GND.

I would recommend using a ready-made jack instead like this.

  1. Once you identify GND and signal, make large solder joints on those.

Step 7: Connect the ADS1115 to the Esp32

This is a big one.

  1. Splice a wire from VDD with the 5V from the CJMCU so both go to 3V3 on the ESP32.
  2. GND goes to GND on the ESP32 (there are two slots for it).
  3. SCL goes to D23.
  4. SDA goes to D21.
  5. ADDR splices with the headphone GND and GND.

Step 8: Connect Audio to ESP32

  1. Solder the headphone jack wire that wasn’t ground to D26 on the ESP32.

Step 9: Connect the Amplifier

  1. Plug the audio jack into the amplifier.
  2. Get your speaker and add + and – wires to the left channel of the amplifier.
  3. Hook up your 10V power supply to the amplifier, but don’t plug it in yet.

Step 10: Attach the EKG Pads

  1. Unpeel the sticky pads on the sensors, then press them onto two different stems of the plant.

Step 11: Program the ESP32

  1. Install the Arduino IDE.
  2. Grab the ESP32 and plug it into your computer.
  3. Then upload the plant.ino code file to the IDE.
  4. Finally, install that onto the ESP32.

Attachments

Step 12: Use the Plant

This is My device working!