Building a Robot Arm: Complete Guide for Makers and Engineers

Introduction

Building a robot arm is one of the most rewarding projects in robotics. You'll learn servo control, kinematics, mechanical design, and programming - all skills that apply to countless other projects.

Required Components

Understanding Servos

Servo motors provide position control. Send them a pulse width and they hold that angle. Key specs to consider:

• Torque (kg·cm): Higher = can lift heavier loads. MG996R has ~10 kg·cm
• Speed (sec/60°): How fast the servo rotates. ~0.17s is typical
• Rotation range: Usually 0-180°, some go 0-270°
• Voltage: Most use 4.8-6V, match your power supply

The Gripper

The gripper (or end effector) is what your arm uses to interact with objects. Common designs:

Robot Arm Kinematics

Arduino Control Code

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>

Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();

// Servo pulse limits (calibrate for your servos)
#define SERVOMIN 150 // ~0 degrees
#define SERVOMAX 600 // ~180 degrees

// Servo channels
#define BASE 0
#define SHOULDER 1
#define ELBOW 2
#define WRIST 3
#define GRIPPER 4

void setup() {
 pwm.begin();
 pwm.setPWMFreq(50); // Servos use 50Hz
 
 // Move to home position
 setServo(BASE, 90);
 setServo(SHOULDER, 90);
 setServo(ELBOW, 90);
 setServo(WRIST, 90);
 setServo(GRIPPER, 30); // Open
}

void setServo(uint8_t channel, int angle) {
 int pulse = map(angle, 0, 180, SERVOMIN, SERVOMAX);
 pwm.setPWM(channel, 0, pulse);
}

void loop() {
 // Pick and place demo
 setServo(GRIPPER, 30); // Open gripper
 delay(500);
 
 setServo(SHOULDER, 45); // Lower arm
 delay(500);
 
 setServo(GRIPPER, 80); // Close gripper
 delay(500);
 
 setServo(SHOULDER, 90); // Raise arm
 delay(500);
 
 setServo(BASE, 180); // Rotate base
 delay(500);
 
 setServo(GRIPPER, 30); // Release
 delay(500);
 
 setServo(BASE, 90); // Return
 delay(1000);
}

Building Tips