Servo motors are essential components in robotics and mechanical electronics projects. Over time, we’ve explored numerous methods for controlling servo motors, such as using an L293D motor driver shield with Arduino Uno (as demonstrated in our Hobby Servo Motor Control with L293D Motor Shield) or employing MATLAB/Simulink with Arduino (explained in Servo Motor Control using Simulink and Arduino).
In this guide, we’ll focus on a new approach: using the RAMPS shield (RepRap Arduino Mega Pololu Shield) to control a servo motor. The servo’s position will be determined by reading an analog signal from a potentiometer. This versatile technique offers precise control and is simple to implement, making it ideal for various DIY projects.
Introduction to the RAMPS Shield
The RAMPS shield is primarily known for its role in 3D printing, but its functionality extends far beyond that. It is also a powerful tool for motor control in robotics and other electromechanical systems. This tutorial will demonstrate how to leverage the RAMPS shield to control a servo motor by interpreting the position of a potentiometer.
What You’ll Need
- Arduino Mega
- RAMPS Shield
- Servo Motor
- Potentiometer
- Connecting Wires
Setting Up the Circuit
The diagram below illustrates the connections for this project:
Hardware Connections
Potentiometer:
- Connect the middle pin of the potentiometer to the analog input pin (A13) on the RAMPS shield.
- Connect the other two pins to 5V and GND, respectively.
Servo Motor:
- Attach the servo motor to the servo pin (D11) on the RAMPS shield.
Setup Overview
This setup ensures that the potentiometer’s position will dictate the angle of the servo motor, creating a simple yet effective control system.
How the Code Works
The control system relies on the Servo library to manage the motor and analogRead() to read the potentiometer’s position. The analog value is mapped to an angular position for the servo, ensuring smooth operation. Additionally, a small threshold is implemented to prevent the servo from reacting to minor fluctuations in the analog signal.
The Code
#include <SPI.h>
#include <Servo.h>
#define T0 13 // Analog Input
#define SERVO0 11 // Servo Pin
Servo myservo; // create servo object to control a servo
int pos;
int prevPos; // variable to hold servo position
const int threshold = 2; // Threshold to avoid small changes causing servo movement
void setup() {
Serial.begin(9600); // Initialize serial port for debugging.
Serial.println("Testing Servo Motor");
pinMode(T0, INPUT_PULLUP); // configure RAMPS TEMP_0_PIN for reading thermistor (MEGA pin 13 from pin_map.h)
myservo.attach(SERVO0); // attach servo object to the servo on SERVO0_PIN (MEGA pin 11 from pin_map.h)
// Sweep servo to test range
for (pos = 0; pos <= 180; pos += 1) {
myservo.write(pos);
delay(15);
}
for (pos = 180; pos >= 0; pos -= 1) {
myservo.write(pos);
delay(15);
}
}
void loop() {
int sensorValue = analogRead(T0); // read temperature from thermistor
Serial.print("sensorValue: ");
Serial.print(sensorValue);
int mappedPos = map(sensorValue, 0, 1023, 180, 0); // map deg C 0-100 to servo degrees 0-180
// Apply hysteresis to prevent small changes from causing rapid servo movements
if (abs(mappedPos - prevPos) >= threshold) {
myservo.write(mappedPos);
prevPos = mappedPos; // Update prevPos only when the servo moves
}
delay(500); // Delay for a short period before the next reading
} How It Works
Setup Phase
- The setup() function initializes serial communication and configures the potentiometer input pin.
- The servo motor is attached to its designated pin and performs a sweep to verify its range of motion.
Main Loop
- The potentiometer’s position is read using analogRead().
- The value is mapped to a servo angle (0° to 180°).
- A hysteresis mechanism ensures the servo only moves when the change in position exceeds a predefined threshold, reducing jitter and unnecessary movements.
Applications
This project has numerous practical applications, including:
- Robotics: Control robotic arms or grippers with precise analog inputs.
- DIY Projects: Integrate the setup into automated systems or custom mechanisms.
- 3D Printing Add-Ons: Enhance your 3D printer with additional servo-controlled components.
Conclusion
The RAMPS shield is a versatile tool that simplifies servo motor control. By combining it with a potentiometer, you can achieve precise, real-time adjustments to the servo’s position. This project demonstrates how to set up and program the RAMPS shield for servo control, opening up possibilities for robotics, DIY electronics, and more.
Experiment with the provided code and expand its functionality by incorporating additional sensors or motors. The RAMPS shield’s flexibility makes it a valuable addition to your electronics toolkit.
