DC Motor Position Control Using Potentiometer – Arduino Compatible

The project presented here is an Arduino-compatible motor control board. The board consists of an ATMEGA328 microcontroller, LMD18201 H-Bridge, and 2 x potentiometers. This closed-loop servo system provides position control using a feedback potentiometer mounted on the output shaft of the gearbox and provides position control by turning the shaft of the reference potentiometer, the motor-gearbox output shaft follows the reference potentiometer. The project can also be used in other applications that require Arduino-compatible hardware and H-Bridge.

The project requires a special mechanism, where the DC motor’s output shaft is mechanically coupled with the potentiometer shaft using a reduction gear. Approx. reduction ratio 15-50: 1. When the reference pot is turned, the motor shaft follows the position. This will provide a maximum rotation of 270 degrees. Multi-rotation is possible with the help of a multiturn potentiometer.

Arduino Code

Arduino example code is available and the board can be programmed using the CN2 connector, the same connector helps burn the boot-loader to a new ATMEGA328 chip.

Refer to the following link for more info about Arduino programming: https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoToBreadboard

This is a modified code, original author of the code: http://geekeeceebee.com

Arduino Pins vs H-Bridge LMD18201

• Arduino D5 = PWM
• Arduino D6 = Direction
• Arduino D8 = Brake (Not Used -Optional)
• Arduino A0 Reference Potentiometer, A1 Feedback Potentiometer

Features

• Power Supply Motor 12V to 40V (48V Max)
• Motor Load 3A (Peak 6A)
• Logic Supply 5V DC @ 20mA
• On Board Jumper J1 for Brake, Closed for Normal Operations
• On Board Programming Connector for Arduino IDE
• Screw Terminals for Motor and Power Supply
• 2 X 3 Pin Male Header for Feedback and Reference Potentiometers
• Arduino Compatible
• PCB Dimensions 47.63 x 42.55mm
• 4 x 3MM Mounting Holes

Connection & Other Details

• CN1: Optional Do Not Install
• CN2: Programming Connector Pin 1 = Tx, Pin 2 = Rx, Pin 3 = Reset, Pin 4 = GND, Pin 5 = VCC, Pin 6 = D11, Pin 7 = D12, Pin 8 = D13
• CN3: Pin 1 = Motor Power Supply, Pin 2 = GND
• MG1: Pin 1 = Motor 1, Pin 2 = Motor 2
• P1: Reference Potentiometer
• P2: Feedback Potentiometer
• J1: the jumper must be closed to enable the Brake for normal operation.

Schematic

Parts List

Connections

Gerber View

Code

//GeeKee CeeBee
// ************ DEFINITIONS************

int potPin = A0;          // Reference Potentiometer
int encoder_pot = A1;    // Position Feedback sensor

int val = 0;
int encoder_val =0;
float kp = 0.2;
float ki = 0.00000 ;
float kd = 2.00;
float Theta, Theta_d;
int dt;
unsigned long t;
unsigned long t_prev = 0;
int val_prev =0;
float e, e_prev = 0, inte, inte_prev = 0;
float Vmax = 12;
float Vmin = -12;
float V = 0.1;
const byte PWMPin = 5;
const byte DirPin1 = 6;
const byte DirPin2 = 8;


//***Motor Driver Functions*****

void WriteDriverVoltage(float V, float Vmax) {
  int PWMval = int(255 * abs(V) / Vmax);
  if (PWMval > 255) {
    PWMval = 255;
  }
  if (V > 0) {
    digitalWrite(DirPin1, HIGH);
    digitalWrite(DirPin2, LOW);
  }
  else if (V < 0) {
    digitalWrite(DirPin1, LOW);
    digitalWrite(DirPin2, HIGH);
  }
  else {
    digitalWrite(DirPin1, LOW);
    digitalWrite(DirPin2, LOW);
  }
  analogWrite(PWMPin, PWMval);

}


void setup() {
  Serial.begin(9600);
  pinMode(DirPin1, OUTPUT);
  pinMode(DirPin2, OUTPUT);

}


void loop() {
  val = analogRead(potPin);                           // Read V_out from Reference Pot
  encoder_val =analogRead(encoder_pot);               // Read V_out from Feedback Pot
  t = millis();
  dt = (t - t_prev);                                  // Time step
  Theta = val;                                        // Theta= Actual Angular Position of the Motor
  Theta_d = encoder_val;                              // Theta_d= Desired Angular Position of the Motor

  e = Theta_d - Theta;                                // Error
  inte = inte_prev + (dt * (e + e_prev) / 2);         // Integration of Error
  V = kp * e + ki * inte + (kd * (e - e_prev) / dt) ; // Controlling Function

  if (V > Vmax) {
      V = Vmax;
      inte = inte_prev;
    }
    if (V < Vmin) {
      V = Vmin;
      inte = inte_prev;
      val_prev= val;
    }
  WriteDriverVoltage(V, Vmax);
  Serial.println(Theta_d); Serial.print(" \t");
    Serial.print(Theta); Serial.print(" \t ");
   t_prev = t;
    inte_prev = inte;
    e_prev = e;
    delay(10);

}

Photos

Video

LMD18201 Datasheet

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