During my final milestone, I faced several problems in the building process of my project. In order to get my robotic arm on the car chassis, I had to use and understand how motor drivers worked. It took time to do research and find documentation about the many components on the motor driver and understanding how everything worked to control the motors was a challenge, as there were some concepts that I was not familiar with. I became focused on the H-bridge of the motor driver and tried to understand everything about it, as the way it worked was important to getting the wheels to rotate properly. Since I was not familiar with a lot of the information, I would find myself not understanding what was happening in a diagram or how something described even worked and eventually was discouraged from working with the motor drivers because I felt that I didn’t know as much. While learning about components is important, I found through this process that physically working and troubleshooting with the component can be a better learning experience than just reading about it in theory. Once I just decided to find examples and use them to show what was going on, I was able to connect what I knew about signals and Arduino to the code and electronics that were going on. I could change the values in the code and immediately see the result, helping to answer questions about how one thing affects another. My frustration about not knowing something enough to use it was solved by jumping into the component and playing around with it to learn more about how it works. Looking back at the research, the different concepts became clearer as I could see them in action, and the extra and detailed information that wasn’t relevant to my project was less of a concern to me. Finding different ways to learn about something and pushing yourself into the unknown is an important way to develop knowledge, and the problem I faced was an example of how you can learn as you fail.

A new tool I used for this project was a soldering iron. By melting solder using an extremely hot iron onto wires, I could connect the DC motors to the motor shield easily. Using the solder took time to learn about safety and the proper technique to make good connections between wires. Through practice and instruction, I learned how to solder wires safely. Another issue with the project was attaching the robotic arm to the car chassis, as there was not enough space for everything needed. I had to plan out where I could put the breadboard and Arduino and rewire the servos to fit better. Placing the motor shield on the underside of the chassis was a good solution to save space and keep the wires between the motors and motor driver separate from the servo wires. Additionally, there was an issue with supplying enough power to the entire arm and car to make sure everything moved smoothly. With limited space, it was hard to find a place for enough battery packs to power everything, making the car heavy. Without sufficient power, the servos would not move smoothly and the motors would fail to turn at all, so providing enough energy to the current was important. Using multiple battery packs and stacking one on top of another was a solution I could find with the large number of batteries I had to use, but it is still an issue of where to put the batteries that I will have to solve. Using zip ties, I was able to connect the arm to the chassis and hold down the batteries to the car. The car chassis was not made for holding a robotic arm on top, so finding solutions to make my modification work was a significant challenge in this milestone. With everything attached to the car chassis, the motors are not functioning as they were expected to, even with enough power. The weight of the arm, breadboard, Arduino, and many batteries has made it so that the wheels are not able to turn without using full power. This was a significant problem in my project, but I plan to fix it by reducing the load and changing the power source in the future. 

Motor drivers help the Arduino to control DC motors.  The component takes a low-current control signal and then turns it into a higher-current signal that can drive a motor. For my project, I used the L298N board as it is a dual motor driver than works with Arduino. There are two main parts to a motor driver; PWM and H-bridge control. The PWM is the signals sent to the enable pins on the motor driver from the PWM pins on the Arduino. By sending a carrying input voltage, the speed of the motors can change from low to high and goes from a range of 0 to 255. The signal is converted to a voltage. The H-bridge controls the rotation the motors are spinning in, which therefore controls which direction the entire car moves. The use of four transistors in an H format with the motor in the middle controls the polarity, which is the direction of the current. Closing a pair of the transistors will cause the current to flow in one direction, turning the motor one way. Closing the opposite pair of transistors will cause the current to flow in the opposite direction, and the motor will rotate the other way. On the physical motor driver, there are output pins where the motor connected to the motor driver, which completes the H-bridge circuit. The control pins at the front control the rotation and speed of the motors. They connect to the digital pins on the Arduino to receive signals, which then tell the motor driver which pair of transistors to open and close to get the specified rotation. The enable pins also control the speed of the motors. The combination of high-low signals to the motor will give its rotation direction, and changing the direction of both the motors will give specific movements. Understanding the motor driver was important in figuring out how to control the car and achieve the movements from the app. 

In the next version of my app for this milestone, I added some new components to control the new features of my project. There is autonomous buttons and a party lights button added to the top, as well as a button to return to the manual mode. To control the car, there are arrow buttons at the bottom.

During this milestone, the majority of the work was getting the Bluetooth to work, making an app to control the robotic arm through Bluetooth, and attaching an ultrasonic sensor to the claw. With the Bluetooth, I had issues with getting the Arduino code to upload to the Arduino when I had the Bluetooth plugged in. Looking further into the documentation about the Bluetooth module, I found that the TX and RX pins on the Bluetooth should only be plugged in after the code is uploaded to the Arduino. This was an important piece of information that I had overlooked when seeing how to work with the Bluetooth. The TX and RX pins on the Arduino are used to also communicate with the computer to upload code. By plugging in the Bluetooth module beforehand, the Arduino could not receive the code from the computer, so simply waiting for the code to uploaded before plugging in those pins fixed the issue I had with the Bluetooth.

Working with the app inventor was a challenge, as I had to learn more about the different features and components, as well as how to use the control structures to send data. Figuring out how to send text to the Bluetooth when a slider or button was changed and creating the best layout for the screen took a significant amount of time. Viewing tutorials about different ways to have features helped to pick up new ideas and implement them. An issue I had with the slider values printing out unusual values was solved when I learned that sliders return decimals, not integers, so learning about the different components helped to reach the goal of using Bluetooth control.

The Bluetooth HC 06 module is how I was able to control the robotic arm from an Android app. The module works on serial communication, so the Android app sends serial data to the module when buttons or sliders are used. The Bluetooth module is connected to the transmit (TX) and receive (RX) pins on the Arduino to send and receive data to the Arduino and computer. The code on the computer takes in the received data from the Arduino and checks specific elements to control the servos and write different angles to the servos. The information from the Android app is sent to the Bluetooth module and then transmitted to the Arduino to control the servos. If the connection between the Bluetooth module and the app is lost, the Bluetooth module transmits a signal to the app to relay that information, and that change is displayed on the app as Not Connected. In my project, I started with a pre-downloaded app to control an LED to learn the basics about using a Bluetooth module. After understanding and grasping the Bluetooth concept, I was able to make my own app using the MIT App Inventor to control the simple LED circuit, and eventually built the project to control the servos and include more user interface. The process of learning about the Bluetooth module and going from serial inputs to user components to send the serial data helped to develop the skills needed to fix problems with the Bluetooth and controls. 

The ultrasonic sensor is used to measure the distance from objects around. The two circles in front of the sensor transmit and receive ultrasound waves, which are used to detect how far away an object is. The sensor emits the waves and then receives the waves once they hit an object and bounce back. The Trig pin of the sensor generates the waves and can be set to high or low for certain amounts of time. The length of the pulse is returned by the Echo pin of the sensor by reading the received waves. The formula Distance = Speed x Time can be used with the speed of sound to calculate the distance between the sensor and the object. These pins are connected to the PWM pins on the Arduino, so the length of the pulses can be controlled by the Arduino. For my project, I used the ultrasonic sensor to detect if an object is within a certain distance, which is measuring the length of the waves emitted and received. If the condition is met, then the claw servo is immediately written to an open position. This means that if an object is within the range, the arm will automatically open up and grab the object, providing another dimension of usability to the project.

The program I used to develop my app was MIT App Inventor. The two parts of the screen design for the user interface and the control structures that send the serial data to the Bluetooth module when the components are used. I was able to customize and layout and colors of the app to my liking with the different options the program has.

While working towards this milestone, I faced a few challenges with the components of the arm. The servos had problems with staying in the angle that they were written to, causing them to shift around instead of staying in place. This was a problem as the robot arm would move erratically, preventing it from performing its task. After researching this issue and receiving guidance, I learned that instability in the power and potentiometer value was causing the pulses to change. My approach to solving the problem was using capacitors to store the energy and smooth the output pulse to the servo, add an external battery to provide a steady supply of energy, and change the code to input a stable value into the servo. Using the external battery was the best option as it was easier to provide a stable energy source without excessively tampering with the servos. In addition, changing the code to compare the potentiometer with an old value from 1 second ago also helped to reduce the jittering by stabilizing the written value to the servo. While trying to adjust one of the servos on the arm, the servo collar broke. I was able to use the hot glue gun to fix the piece, and the process taught me to not only be careful with the pieces I am using but also to be prepared for some pieces to break in the building process.