12. Mechanical Design, Machine Design

This week, I worked on was making a PCB.

Group Task:

Group task

List of components:

Quantity	Component	Value / Model	Description
1	Microcontroller	XIAO ESP32-s3	Main microcontroller
2	Motor driver	A4988	Stepper motor driver
1	Voltage regulator	L7805	5V voltage converter
2	Electrolytic capacitor	100 µF	Power filtering
1	Electrolytic capacitor	10 µF	Regulator input capacitor
1	Electrolytic capacitor	22 µF	Regulator output capacitor
2	Resistor	1 kΩ	Pull-down for endstops
3	Connector	Header	Motor outputs
1	Connector	Header	Buzzer
2	Connector	Header	Endstop inputs
1	Connector	Header	Z-axis servo
2	Connector	Header	Endstops 1 and 2
1	Connector	Header	OLED display
1	Connector	Header	Extra pin
1	Connector	Header	Common GND

• First, I made the schematic.

In the PCB, I marked the bridges that I used to connect the components. To make these bridges, I used 0-ohm resistors.

First, I drilled the holes, engraved the PCB, and cut the contour. To see the specifications, you can check my Electronics Production task.

First ,I soldered the resistors like a bridges and then the other components.

I was nervous because I didn’t know how the PCB would react, so I started by moving a servo. Then, I moved the motors.

This is the code for the stepper motors:

#define STEP1 6
#define DIR1 7
#define STEP2 8
#define DIR2 9

void setup() {
pinMode(STEP1, OUTPUT);
pinMode(DIR1, OUTPUT);
pinMode(STEP2, OUTPUT);
pinMode(DIR2, OUTPUT);
}

void loop() {
// Motor 1 - Una vuelta completa (400 pasos en 1/2 paso)
digitalWrite(DIR1, HIGH);
for (int i = 0; i < 400; i++) {
digitalWrite(STEP1, HIGH);
delayMicroseconds(800);
digitalWrite(STEP1, LOW);
delayMicroseconds(800);
}

delay(1000);

// Motor 2 - Una vuelta completa (400 pasos en 1/2 paso)
digitalWrite(DIR2, LOW);
for (int i = 0; i < 400; i++) {
digitalWrite(STEP2, HIGH);
delayMicroseconds(800);
digitalWrite(STEP2, LOW);
delayMicroseconds(800);
}

delay(2000);
}

• Most boards have a switch to choose whether they are powered by an external source or by USB, in case both are connected at the same time. But the XIAO doesn't have one, so what happened was that we powered the XIAO with both the external source and the computer, and the XIAO burned out.
• However, the rest of the board was intact, so we had to solder a new XIAO. We also cut the 5V power line from the external source to the XIAO and only kept the power from the computer to avoid voltage issues.

Finally, to mount the LCD, I made a 3D piece. To secure the board to the case, I made screws. I used a Prusa printer.

Files

• 3D designs
• Box design
• PCB design in KiCad

Conclusion🛸🛸

It was a challenge to understand how a CNC works, including each of its parts and the electronic components that make it work. As a team, we also learned things we didn't know about, like the problem with the XIAO, which will be useful in future projects.