28BYJ 48 Stepper Motor Arduino Reference
Servo Motor Reference

These were helpful when drawing the schematic diagram.

1 / 4

2 / 4

3 / 4

4 / 4

❮ ❯

Image Sources:

28BYJ 48 Pinout and Wiring Diagram
ULN2003 to Unipolar Stepper Motor Circuit
NCP1117 Voltage Regulator Datasheet

KiCAD - PCB Board Editor

The whole view of the board design. Notice the difference in trace thickness ? The trace thickness was changed to handle the different power requirements on the board and to reduce the risk of overheating.

To add traces thickness. FILE > BOARD SETUP. Follow the image. Enter the value and click enter. Then click okay.

When drawing the traces select the vlaue from the TRACK -drop down box. The trace drawn next would have the selected thickness

Normally, we used a trace width of 0.4 mm for most connections. However, since this board uses a 12V power supply, so increased the width of the traces carrying higher current. The 12V and GND traces were set to 1mm width. The 5V power traces were set to 0.8 mm width. Signal traces carry very little current, so they were kept at 0.4mm width.

Download and Import Footprint

1 / 3

2 / 3

3 / 3

❮ ❯

ULN2003 SnapEDA Footprint

Update / Change Footprint

1 / 3

2 / 3

3 / 3

❮ ❯

TOUCH PAD - How to.

Draw a rectangle. Double click on it. It opens the Properties box.
Choose Corners by Box.
Select Filled Shape.
Line Style: Solid.
Net: Touch Pad. I am choosing this because this is the label I had used for touch. This is a very important step. This decides which net class the rectangular shape is. If I choose power or ground, then it acts like that.
Layer: F.Cu because I am using the front side of the copper clad.
Click OK.

3D Views

The front view.

The back view. Shows the drills.

Milling & Soldering

Refer WEEK 8 to know about the Milling & Soldering process

Roland Modela milling machine used for PCB milling

PCB board after milling

Components placed on the PCB board for soldering

just to show how the vertical header pin was connected on the baord

PCB board and the electronic components that will be used for assembly

JST connector of the stepper motor connected to the PCB board

Testing

Power consumption testing setup for the board

The arrangement is similar to the power consumption testing setup used in the group project.

Testing if the stepper motor works

The rotation of the servo was restricted by holding it from moving. The torque capacity of the servo is less than the load created by the resisting force applied. This shows that the servo consumes more current trying to overcome that resisting force.

Board connections and external power supply setup

The board connections are shown above. It requires power from the Owon power supply because I designed the traces so that the XIAO and the servo motor receive power from the 12V supply.

Finally lets code -Arduino

Servo motor- Sweep- Arduino example

I tested the servo with an example code available in ardunio. If the libray is not available install Servo by Arduino / Michael Margolis. Usually the library comes with Ardunio. File > Examples > Servo > Sweep

    /* Sweep
  by BARRAGAN <http://barraganstudio.com>
  This example code is in the public domain.

  modified 28 May 2015
  by Michael C. Miller
  modified 8 Nov 2013
  by Scott Fitzgerald

  http://arduino.cc/en/Tutorial/Sweep
*/

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards


void setup() {
  myservo.attach(D0);  // attaches the servo on GIO2 to the servo object
}

void loop() {
  int pos;

  for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
  for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
}

for (pos = 0; pos <= 180; pos += 1) this is to move the arm of the servo from 0 degree to 180 degree. With 500 millisecond delay.
Then the for (pos = 180; pos >= 0; pos -= 1)makes the arm to move back 180 degree, making it to the starting position. After 500 miliseconds it moves according to the prevous code.

Stepper motor- Sweep- Arduino example

I tested the 28byj48 12V stepper motor with an example code available in ardunio. Usually the library is built-in Ardunio. File > Examples > Stepper > stepper_oneRevolution

    
/*
 Stepper Motor Control - one revolution

 This program drives a unipolar or bipolar stepper motor.
 The motor is attached to digital pins 8 - 11 of the Arduino.

 The motor should revolve one revolution in one direction, then
 one revolution in the other direction.


 Created 11 Mar. 2007
 Modified 30 Nov. 2009
 by Tom Igoe

 */

#include <Stepper.h>

const int stepsPerRevolution = 200;  // change this to fit the number of steps per revolution
// for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, D7, D8, D9, D10);

void setup() {
  // set the speed at 60 rpm:
  myStepper.setSpeed(100);
  // initialize the serial port:
  Serial.begin(9600);
}

void loop() {
  // step one revolution  in one direction:
  Serial.println("clockwise");
  myStepper.step(stepsPerRevolution);
  delay(500);


}


  

  // initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, D7, D8, D9, D10);

These are the 4 pins of the microcontroller to which the ULN2003 is connected. It has to be named as shown, or else Arduino doesn't recognise it.

myStepper.step(stepsPerRevolution);

The rotation is in the clockwise direction. The speed is set at 100 RPM by me for the movement to be visible, though the suggested one in the code was 60 RPM.

If the rotation was to be in the anticlockwise direction, then it has to be changed to
myStepper.step(-stepsPerRevolution);. A (minus) - sign is added.

Capacitive Touch + Servo - Xiao Rp2040

Mentioning the microcontroller's name and the pins are important and you can also upload the KiCAD drawing.I mentioend the names of the pins

    #include <Servo.h>

// Pin Definitions
const int TOUCH_PIN = D6; // Connected to your PCB pad
const int SERVO_PIN = D0; // Servo control pin

Servo myServo;

// Threshold for touch detection (adjust based on PCB sensitivity)
const int TOUCH_THRESHOLD = 20000; 

void setup() {
  Serial.begin(115200);
  myServo.attach(SERVO_PIN);
  
  // Initialize servo at 0 degrees
  myServo.write(0);
  
  pinMode(TOUCH_PIN, INPUT);
  Serial.println("System Initialized. Touch the ARDRA pad!");
}

void loop() {
  long touchValue = readCapacitivePin(TOUCH_PIN);

  // If the sensor value exceeds our threshold, trigger the servo
  if (touchValue < TOUCH_THRESHOLD) {
    Serial.print("Touch Detected! Value: ");
    Serial.println(touchValue);
    
    // Perform "one turn" 
    // Note: Standard servos move 0-180. 
    // If it's a 360 continuous servo, this dictates speed/time.
    // Assuming standard 180-degree servo:
    myServo.write(180); 
    delay(1000);        
    myServo.write(0);   
    delay(500);         // Debounce delay
  }
  
  delay(10);
}

// Simple capacitive sensing function for RP2040
long readCapacitivePin(int pinToMeasure) {
  long total = 0;
  for (int i = 0; i < 10; i++) {
    pinMode(pinToMeasure, OUTPUT);
    digitalWrite(pinToMeasure, LOW);
    delayMicroseconds(10);
    
    pinMode(pinToMeasure, INPUT);
    long cycles = 0;
    while (digitalRead(pinToMeasure) == LOW && cycles < 2000) {
      cycles++;
    }
    total += cycles;
  }
  return total;
}
  

Serial.begin(115200); Set the baud rate to this value so the Serial Monitor output is readable.

const int TOUCH_THRESHOLD = 20000; This is the threshold value that is set.

myServo.write(0); This is the position of the servo arm.

if (touchValue < TOUCH_THRESHOLD) {
    Serial.print("Touch Detected! Value: ");
    Serial.println(touchValue);

The touch value is the threshold value when the pad is touched. The touch value is less than the set threshold value.

What happened on my board was that I forgot to add a 1M ohm resistor, which would have made it a pull up resistor. However, the touch pad still worked. The Serial output was constantly displaying "Touch Detected". The threshold value changed when the pad was touched. This was actually caused by electrical noise from the body. This caused the servo to move.

So, the servo arm moves to 180 degrees and waits for 1000 milliseconds, then comes back to 0 degrees and waits for 500 milliseconds before moving again if a touch has been detected.

delay(10); This delay of 10 milliseconds is for the MCU to reset.

Troubleshooting

To be honest, I found that my board was missing the resistor long after this week. Until then, I was like something is wrong and the touch was not working, and later it worked.

Why the board could have failed
What happened on my board was that I forgot to add a 1M ohm resistor, which would have made it a pull up resistor. In capacitive resistance, the touch increases the capacitance, which would take longer time for the current to overcome the capacitance. It delays the charging time. This in turn increases the cycle count. This increases the touch value.
Therefore, the condition should have been touchValue > TOUCH_THRESHOLD.

Why it didnt fail in the way it could have
I was ranting to Gemini or ChatGPT that the board was not detecting touch, and it might have changed the condition in the code to touchValue < TOUCH_THRESHOLD. Because of this, the touch value did not have to be higher than 20000 (TOUCH_THRESHOLD) to be detected.

What was happening inside
As the condition is touchValue > TOUCH_THRESHOLD, without the resistor the pin is floating. Even the air or electrical disturbance was causing the touch to be detected. This was why the board printed "TOUCH DETECTED" even without me touching the board.

What could have been a solution
The board would have worked perfectly by adding that 1M ohm resistor and using the condition touchValue > TOUCH_THRESHOLD.

Download Week 10 Zip File