Choosing DC, Servo and Stepper Motors for Your Robot Project

#include <Servo.h>

// --- DC motor on TB6612FNG channel A ---
const int PWMA = 5;
const int AIN1 = 7;
const int AIN2 = 8;
const int STBY = 4;

// --- Servo signal ---
const int SERVO_PIN = 9;   // note: Servo library disables PWM on pins 9 and 10 on the Uno
Servo armServo;

// --- Stepper on A4988 (full-step mode) ---
const int STEP_PIN = 2;
const int DIR_PIN  = 3;
const int STEPS_PER_REV = 200;  // 1.8 degree stepper

void dcMotor(int speed) {         // speed -255..255
  digitalWrite(AIN1, speed >= 0 ? HIGH : LOW);
  digitalWrite(AIN2, speed >= 0 ? LOW : HIGH);
  analogWrite(PWMA, abs(speed));
}

void stepperMove(int steps, bool clockwise, unsigned int usPerStep) {
  digitalWrite(DIR_PIN, clockwise ? HIGH : LOW);
  for (int i = 0; i < steps; i++) {
    digitalWrite(STEP_PIN, HIGH);  // A4988 steps on the rising edge
    delayMicroseconds(5);
    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(usPerStep);  // larger delay = slower rotation
  }
}

void setup() {
  pinMode(PWMA, OUTPUT); pinMode(AIN1, OUTPUT);
  pinMode(AIN2, OUTPUT); pinMode(STBY, OUTPUT);
  digitalWrite(STBY, HIGH);        // take TB6612FNG out of standby
  pinMode(STEP_PIN, OUTPUT); pinMode(DIR_PIN, OUTPUT);
  armServo.attach(SERVO_PIN);
}

void loop() {
  // 1. DC motor: ramp up forward, then reverse, then stop
  for (int s = 0; s <= 200; s += 10) { dcMotor(s); delay(50); }
  delay(1000);
  dcMotor(-150); delay(1000);
  dcMotor(0);    delay(500);

  // 2. Servo: move to three angles and hold each one
  armServo.write(0);   delay(800);
  armServo.write(90);  delay(800);
  armServo.write(180); delay(800);

  // 3. Stepper: exactly one revolution each way
  stepperMove(STEPS_PER_REV, true, 2000);
  delay(500);
  stepperMove(STEPS_PER_REV, false, 2000);
  delay(1000);
}