Published March 18, 2026 © GPL3+

Smars rc rover Esp32 360 degree servo

The popular 3d printed chassis smars got an update- continuos servos and some Esp32 power!

AdvancedFull instructions provided2 hours561

Things used in this project

Hardware components

Espressif ESP32 Development Board - Developer Edition

SG90 Micro-servo motor

mp1504en buck converter

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Digilent Mastech MS8217 Autorange Digital Multimeter

Premium Female/Male Extension Jumper Wires, 40 x 6" (150mm)

Story

Have you ever accidentally bought 360 degree servos or just have 2 laying around? this project is for you! It uses an Esp32, 2 360 degree sg90 servos, 2 18650 batteries, MP1504en, a custom 3d printed breakout board(https://www.printables.com/model/68885-esp32-breadboard), modified smars chassis (https://www.thingiverse.com/thing:2831501). and 18650 battery holder. You can 3d print your own battery holder or just buy one (https://www.thingiverse.com/thing:2821437)

Libraries used: ESP32Servo— by Kevin Harrington

Start by removing the servo tab of your 2 servos and screwing them in with some small self tapping screws included with the servos. After, click in place the 9v battery holder element to the left. Click on the 3d printed slave wheels and screw on the 360 degree servo modified wheels with the servo horns inside.

servo position and 9v battery holder element to the left

Feed the servo wires through the hole of the 3d printed plate element and glue it to the inside of the chassis. Use filament pieces to connect the tracks(32).

plate element glued

Next connect the battery holder and 3d printed breadboard (breakout board). Solder the buck converter to the batteries. Use the multimeter to measure and set no more than 5volts, min.4.8 on the buck converters output. when done, glue the whole thing on top.

1 / 2

After connect the buck converters positive (5v output) to the Esp32 VIN, and negative wire to GND of the Esp32. Connect the left servo to D13 and right servo to D12. Connect both 5v and gnd of the servos to the esp32 gnd and 5v/VIN.

Lastly tuck in the loose servo wires and upload code. Do not plug in batteries and pc at same time! After upload, disconnect the robot and plug in the batteries. On your phone open the wifi and connect to the robot.

const char* AP_SSID = "SMARS-Rover";

const char* AP_PASSWORD = "rover1234";

And open browser and type in 192.168.4.1

Use the two sliders as controls and enjoy!

Code

code

#include <WiFi.h>
#include <WebServer.h>
#include <ESP32Servo.h>

const char* AP_SSID     = "SMARS-Rover";
const char* AP_PASSWORD = "rover1234";

#define SERVO_LEFT_PIN  13
#define SERVO_RIGHT_PIN 12
#define LEFT_STOP       92
#define RIGHT_STOP      92
#define DEADZONE        0.08f

WebServer server(80);
Servo servoLeft, servoRight;

const char B64[] =
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String decodeB64(const char* src) {
  const char* b64c = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  String out = "";
  int val = 0, valb = -8;
  for (const char* p = src; *p; p++) {
    const char* pos = strchr(b64c, *p);
    if (!pos) continue;
    val = (val << 6) + (pos - b64c);
    valb += 6;
    if (valb >= 0) { out += (char)((val >> valb) & 0xFF); valb -= 8; }
  }
  return out;
}

void setLeft(float v) {
  if (fabs(v) < DEADZONE) { servoLeft.write(LEFT_STOP); return; }
  servoLeft.write(LEFT_STOP - (int)(v * 89));
}

void setRight(float v) {
  if (fabs(v) < DEADZONE) { servoRight.write(RIGHT_STOP); return; }
  servoRight.write(RIGHT_STOP + (int)(v * 89));
}

void stopAll() {
  servoLeft.write(LEFT_STOP);
  servoRight.write(RIGHT_STOP);
}

void setup() {
  Serial.begin(115200);
  servoLeft.attach(SERVO_LEFT_PIN);
  servoRight.attach(SERVO_RIGHT_PIN);
  servoLeft.write(LEFT_STOP);
  servoRight.write(RIGHT_STOP);
  delay(500);
  stopAll();

  WiFi.softAP(AP_SSID, AP_PASSWORD);
  Serial.println(WiFi.softAPIP());

  String page = decodeB64(B64);
  server.on("/", [page]() { server.send(200, "text/html", page); });
  server.on("/drive", []() {
    float l = server.arg("l").toFloat();
    float r = server.arg("r").toFloat();
    setLeft(l);
    setRight(r);
    server.send(200, "text/plain", "ok");
  });
  server.begin();
  Serial.println("Ready: http://192.168.4.1");
}

void loop() {
  server.handleClient();
}