Seed Dropper System

Small-scale planting can be repetitive and inconsistent. At the same time, old or broken 3D printers often still have usable motion systems. I wanted to explore whether a discarded fabrication tool could be repurposed into a useful planting machine.

The value of this project is not that it solves farming at scale. The value is that it shows how an existing machine can be reimagined as a new tool through design, fabrication, and physical computing.

The concept was to use the printer as a positioning system. The printer moves to specific X/Y coordinates above the soil bed, pauses, and the seed dropper releases seeds through a tube.

The system splits responsibility between the printer and the seed dropper. The printer handles precise positioning, while the ESP32 and servo handle seed release. Explore the model, then scroll through the build →

The software was split into two parts. The Python GUI gave me a simple control panel to send commands. The ESP32 listened for serial text commands and translated them into servo angles.

Serial command protocol

Text in, motion out. Anything that isn't a named command is treated as a raw servo angle.

OPEN     → servo to 180°
CLOSE    → servo to 60°
DROP1    → open, wait 400ms, close (single seed)
DROP3    → repeat drop 3× with 400ms gaps
0–180    → raw angle for manual tuning

Python GUI — Tkinter + pyserial

Buttons fire named commands; the slider streams integer angles as they change.

import tkinter as tk
import serial

ser = serial.Serial('/dev/cu.usbserial-0285FFE6', 115200)

def send(cmd):
    ser.write((cmd + "\n").encode())

root = tk.Tk()
root.title("Seed Servo Control")
root.geometry("400x400")

slider = tk.Scale(root, from_=0, to=180,
                  orient="horizontal",
                  command=lambda v: send(v))
slider.pack(fill="x", padx=20, pady=20)

tk.Button(root, text="OPEN",   command=lambda: send("OPEN")).pack(fill="x")
tk.Button(root, text="CLOSE",  command=lambda: send("CLOSE")).pack(fill="x")
tk.Button(root, text="DROP 1", command=lambda: send("DROP1")).pack(fill="x")
tk.Button(root, text="DROP 3", command=lambda: send("DROP3")).pack(fill="x")

root.mainloop()

ESP32 firmware — Arduino + ESP32Servo

Reads a line, matches it against the protocol, and writes to the servo on GPIO 13.

#include <ESP32Servo.h>

Servo myServo;

const int SERVO_PIN = 13;

int openAngle  = 180;
int closeAngle = 60;

void setup() {
  Serial.begin(115200);
  myServo.setPeriodHertz(50);
  myServo.attach(SERVO_PIN, 500, 2400);
  myServo.write(closeAngle);

  Serial.println("READY");
}

void loop() {
  if (Serial.available()) {
    String cmd = Serial.readStringUntil('\n');
    cmd.trim();

    if (cmd == "OPEN") {
      myServo.write(openAngle);
    }
    else if (cmd == "CLOSE") {
      myServo.write(closeAngle);
    }
    else if (cmd == "DROP1") {
      myServo.write(openAngle);
      delay(400);
      myServo.write(closeAngle);
    }
    else if (cmd == "DROP3") {
      for (int i = 0; i < 3; i++) {
        myServo.write(openAngle);
        delay(400);
        myServo.write(closeAngle);
        delay(400);
      }
    }
    else {
      int angle = cmd.toInt();
      if (angle >= 0 && angle <= 180) {
        myServo.write(angle);
      }
    }
  }
}

The final prototype demonstrated a working planting flow: the printer moved to set coordinates, paused, and the seed dropper released seeds through a controlled mechanism.

This project taught me how to repurpose existing hardware into a new tool — sustainability through reuse, not just material choice.