Servo-Controlled Robot Arm

What You'll Build

You will build a small robot arm with three moving joints, each controlled by turning a knob. Twist the first knob and the base rotates, the second lifts the arm, the third opens and closes the gripper. Once it works you can record a sequence of positions and let the arm repeat the movement by itself.

What You Need

• ✓Arduino Uno
• ✓3 × SG90 servo
• ✓3 × potentiometer
• ✓External 5V supply
• ✓Breadboard

How It Works

A servo is a motor that knows its own angle. You tell it 'go to 90 degrees' and it gets there and holds. Each potentiometer gives the Arduino a number from 0 to 1023 as you turn it, and the map() function converts that range into an angle from 0 to 180. Read, map, write — repeated many times a second, that feels like smooth remote control.

Before You Wire It

Wiring

Step-by-Step Instructions

1. 1

   Assemble the joints

   Build from the bottom up: base servo, then shoulder, then the gripper. Centre every servo at 90° before you screw its horn on, or the arm will hit its own limits.

2. 2

   Power the servos properly

   Servo current varies with model and load and rises sharply during a stall. Ask an adult to check the servo datasheet and choose a regulated 5 V supply with enough current for all three. Run servo grounds to that supply and join supply GND to Arduino GND. Disconnect power before rewiring. If a servo buzzes hard, stalls, pinches, or gets hot, cut power immediately and let it cool before touching it.

3. 3

   Wire the knobs

   Each potentiometer is a voltage divider you can turn. The middle pin carries the changing voltage to an analog input.

4. 4

   Add smoothing

   Raw analog readings jitter slightly, which makes servos buzz. Average a few readings or ignore changes smaller than two degrees.

5. 5

   Record a routine

   Once you enjoy driving it manually, store a list of angles in arrays and play them back to automate a pick-and-place move.

Arduino Code

#include <Servo.h>

Servo base, elbow, grip;

int smooth(int pin) {
  long total = 0;
  for (int i = 0; i < 8; i++) total += analogRead(pin);
  return total / 8;
}

void setup() {
  base.attach(9);
  elbow.attach(10);
  grip.attach(11);
}

void loop() {
  base.write(map(smooth(A0), 0, 1023, 0, 180));
  elbow.write(map(smooth(A1), 0, 1023, 15, 165));
  grip.write(map(smooth(A2), 0, 1023, 30, 110));
  delay(15);
}

Understanding the Code

Challenges & Upgrades

Troubleshooting

Helpful Resources