Week 10. Output Devices

Group Assignment

From this group project, I learned a lot about how output devices work and how to measure their power use. We used tools like the Instek GPD-3303D power supply and ACS712 sensor to check how much energy different devices, like LED strips and DC motors, consume. I found it interesting that when the load on the motor increases, it uses more power. The most power is used when the motor is completely stopped.



I also practiced using equipment like multimeters and learned how to control motor speed with PWM (pulse width modulation). We even created a smart way to help the motor start and save energy. This task showed me the importance of accurate tools and how we can make devices work more efficiently.

Individual Assignmet

Making Final Board

This week, I started PCB milling again, and I finally made one of my final project boards. This time, I used the ATtiny3216 microcontroller because it has 20 pins, and every pin is very important to me. My submarine will have quite a lot of input and output devices.



Using the pinouts I found on the internet, I created a table and added all the data I need for programming.

Pin #	Pin Type	Programming Pin	Description
VCC	POWER	VCC	Power supply
PA0	PORT PIN/PROGRAMMING	17	Analog/Digital I/O; UPDI
PA1	PORT PIN	14	Analog/Digital I/O
PA2	PORT PIN	15	Analog/Digital I/O
PA3	PORT PIN	16~	Analog/Digital I/O
PA4	PORT PIN	0~	Analog/Digital I/O
PA5	PORT PIN	1~	Analog/Digital I/O
PA6	PORT PIN	2	Analog/Digital I/O
PA7	PORT PIN	3	Analog/Digital I/O
PB0	PORT PIN	9~	Analog/Digital I/O; SCL
PB1	PORT PIN	8~	Analog/Digital I/O; SDA
PB2	PORT PIN	7~	Digital I/O; TXD
PB3	PORT PIN	6	Digital I/O; RXD
PB4	PORT PIN	5	Analog/Digital I/O
PB5	PORT PIN	4	Analog/Digital I/O
PC0	PORT PIN	10	Digital I/O
PC1	PORT PIN	11	Digital I/O
PC2	PORT PIN	12	Digital I/O
PC3	PORT PIN	13	Digital I/O
GND	GROUND	GND	Ground connection

Here is how my PCB looks, and yes, it is also double-sided.



I decided to make everything look nice and exported the board as a STEP file. Then, I imported it into Fusion 360 and designed a case for it to ensure safe operation during programming. I also added labels for the pinouts, which makes all the terminals much clearer.

Since everything was already ready, I started milling the PCB.



After milling, I first soldered the vias using pin headers to connect the tracks on both sides.



After soldering the vias, I started soldering all the other components.



Then, I exported the sketch of the board’s box and started preparing for the cutting.



Here are the cut details.



I also printed spacers to set the height between the bottom and the board.



Then, I first screwed the board to the bottom of the box and later assembled all the other details.



I also made an extension for programming using UPDI and attached it to the lid of the box to make programming easier.



Here’s how it looks when assembled.



The labels look great, and all the pins are very well described.

Programing

Since I will have 3 fins on the submarine, I need to have 3 servo motors to control them. I decided to try making some balancing system.)



For this, I decided to use the GY-521 accelerometer and 3pc HK15138 servo motors.

Here is short information about HK 15318 Servo Motor what I found in Network.

Parameter	Specification
Model	HK 15318
Operating Voltage	4.8V to 6.0V
Operating Speed	0.16 sec/60° (at 4.8V)
Torque	3.5 kg-cm (at 4.8V)
Weight	55 g
Motor Type	DC Motor
Gear Type	Plastic
Rotation Angle	180°

And also about GY-521 Accelerometer

Parameter	Specification
Model	GY-521 (MPU-6050)
Type	Accelerometer + Gyroscope
Operating Voltage	3.3V to 5V
Interface	I2C
Accelerometer Range	±2g, ±4g, ±8g, ±16g
Gyroscope Range	±250, ±500, ±1000, ±2000 °/s
Resolution	16-bit ADC
Sampling Rate	1kHz (up to 8kHz in high-speed mode)
Weight	~3.5 g
Features	Onboard Digital Motion Processor (DMP), 6-axis motion tracking, temperature sensor
Output Data	Accelerometer, Gyroscope, Temperature
Power Consumption	~3.9mA (typical)

Since I’m not very good at programming, I asked ChatGPT for help in creating the code. However, I have learned the code, and now I can say that I understand how it works!
Prompt:

Write a simple code for the ATtiny3216, where I have 3 servo motors for the submarine. One of the servo motors turns the submarine left and right, and the other 2 get the same >signal to control diving or going up. I also have a GY-521 accelerometer, so I need a code to stabilize the submarine using the accelerometer and the 3 servos. When there is an imbalance, the servos should change position. Once the submarine is balanced, the servos should return to the initial position, and the motor should turn off. This should be very simple. I hope you write it well, but let me show you where I connected everything to write the code with the correct pins:
- Servo1 > PA1 (Pin 14)
- Servo2 > PA2 (Pin 15)
- Servo3 > PA3 (Pin 16) (Servo2 does the same as Servo3)
- Accelerometer SCL > PB0 (Pin 9)
- Accelerometer SDA > PB1 (Pin 8)

Here’s what it gave me:

#include <Wire.h>
#include <Servo.h>

// Define servos
Servo servo1; // Left-right control
Servo servo2; // Dive control
Servo servo3; // Dive control (same as servo2)

// MPU6050 Accelerometer
const int MPU6050_ADDR = 0x68;
const int servo1Pin = 14; // PA1
const int servo2Pin = 15; // PA2
const int servo3Pin = 16; // PA3
const int SCL_PIN = 9; // PB0
const int SDA_PIN = 8; // PB1

int16_t ax, ay, az;
int currentPos1 = 90; // Initial positions
int currentPos2 = 90;
int currentPos3 = 90;

void setup() {
    Wire.begin();
    Serial.begin(9600);

    servo1.attach(servo1Pin);
    servo2.attach(servo2Pin);
    servo3.attach(servo3Pin);

    // Initialize MPU6050
    Wire.beginTransmission(MPU6050_ADDR);
    Wire.write(0x6B); // Power management register
    Wire.write(0);    // Wake up the sensor
    Wire.endTransmission();

    servo1.write(currentPos1);
    servo2.write(currentPos2);
    servo3.write(currentPos3);
}

void loop() {
    readAccelerometer();

    // Check for imbalance in multiple axes
    if (abs(ax) > 1000 || abs(ay) > 1000 || abs(az - 16384) > 2000) { // 16384 is approx. 1G
        smoothAdjustServos();
    } else {
        smoothResetServos();
    }

    delay(100);
}

void readAccelerometer() {
    Wire.beginTransmission(MPU6050_ADDR);
    Wire.write(0x3B); // Starting register for accelerometer data
    Wire.endTransmission();
    Wire.requestFrom(MPU6050_ADDR, 6);

    ax = Wire.read() << 8 | Wire.read();
    ay = Wire.read() << 8 | Wire.read();
    az = Wire.read() << 8 | Wire.read();
}

void smoothAdjustServos() {
    int targetPos1, targetPos2;

    // Set target positions based on accelerometer data
    targetPos1 = map(ax, -2000, 2000, 60, 120); // Left-right control
    targetPos2 = map(ay, -2000, 2000, 60, 120); // Dive control

    // Smoothly adjust servo1 position
    if (currentPos1 < targetPos1) currentPos1++;
    else if (currentPos1 > targetPos1) currentPos1--;

    // Smoothly adjust servo2 and servo3 positions
    if (currentPos2 < targetPos2) currentPos2++;
    else if (currentPos2 > targetPos2) currentPos2--;

    currentPos3 = currentPos2; // Keep servo3 synced with servo2

    // Write new positions to servos
    servo1.write(currentPos1);
    servo2.write(currentPos2);
    servo3.write(currentPos3);
}

void smoothResetServos() {
    int targetPos = 90; // Neutral position

    // Smoothly reset servo1
    if (currentPos1 < targetPos) currentPos1++;
    else if (currentPos1 > targetPos) currentPos1--;

    // Smoothly reset servo2 and servo3
    if (currentPos2 < targetPos) currentPos2++;
    else if (currentPos2 > targetPos) currentPos2--;

    currentPos3 = currentPos2; // Keep servo3 synced with servo2

    servo1.write(currentPos1);
    servo2.write(currentPos2);
    servo3.write(currentPos3);
}

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Last update: April 2, 2025