Week 8- Journal

For this week’s assignment, my idea is to build a Bluetooth-enabled Arduino electronic safe. The safe can be unlocked with a secret code entered on the keypad and wirelessly via a phone/PC GUI through a Bluetooth module, making it both practical and interactive. I care about this idea because it blends security concepts with smart home technology, showing how everyday objects can be automated and enhanced with wireless control. I was inspired by online Arduino safe projects like Wokwi and tutorials that demonstrate how servo locks and keypads can be integrated into real-world applications. The addition of wireless control modernizes the project and connects it to IoT trends, making it both educational and useful.

Source: Wokwi

Inputs and Action Outputs: 

Inputs

1. Serial (Bluetooth / PC)

   • Digits (0–9) → used for entering the 4-digit password.

   • Characters (R, G, B, Y, C, M) → commands to control the RGB LED.
     
     

2. User password entry

   • A 4-digit string typed through Serial.
     
     

Action Outputs

1. Servo Motor (Lock/Unlock)

• lockDoor() → Servo at 0° (locked

• unlockDoor() → Servo at 90° (unlocked)
  
  

2. Buzzer

• lockDoor() → Short beep (“click”) when locking.

• alarm() → Repeated ON/OFF beeps (5 times) when wrong password entered.
  
  

3. RGB LED

• Commands from Serial:

  • R → Red

  • G → Green

  • B → Blue

  • Y → Yellow (Red + Green)

  • C → Cyan (Green + Blue)

  • M → Magenta (Red + Blue)

• turnOffRGB() turns LED off at startup.
  
  

4. LCD Display (16x2 I2C)

• Startup → “Safe Door System” → then “Enter Code:”

• Password entry → Displays **** instead of real digits

• Correct password → “Access Granted” → then “Enter New Code:”

• Wrong password → “Access Denied”

• New code saved → “New Code Saved”
  
  

5. Serial Monitor (Feedback)

• Prints messages like:

  • "System Ready. Type 4 characters..."

  • "Password entered: XXXX"

  • "Access Granted" / "Access Denied"

  • "New password set: XXXX"

  • "LED: RED", "LED: BLUE", etc.
    
    

In short:

• Inputs = Password digits + RGB commands (via Serial/Bluetooth)

• Outputs = Servo motion, buzzer sounds, RGB LED colors, LCD messages, Serial feedback

Design

Wokwi:.

Step 1: Start Project

• Opened Wokwi Arduino Simulator.

• Choose Arduino UNO as the microcontroller.

Step 2: Add and Connect Components

• LCD 16x2 I2C

  • Connected SDA → D19, SCL → D18, VCC → 5V, GND → GND.

• Servo Motor

  • Control wire → Pin 9,

  • Power → 5V,

  • Ground → GND.
    
    

• Buzzer

  • Positive → Pin 8,

  • Negative → GND.
    
    

• RGB LED (common cathode)

  • Red → Pin 3,

  • Green → Pin 4,

  • Blue → Pin 5,

  • Common cathode → GND.
    
    

Step 3: Upload the Code  (Wokwi IDE)

• Copied the Arduino code into Wokwi’s IDE.

• Ran simulation → Observed LCD messages, servo movement, LED color changes, and buzzer sounds (visual indicator in Wokwi).

 Implementation in Arduino Bluetooth on mobile: 

• Change Button Configuration to (R, G, B, Y, C, M)

• And for Serial Monitor: Just enter the code 

Video For the Circuit Working:

Ai-Assisted Code:

AI-Assistance

1. The work of AI was not the majority. It helped me to deal with the issues I faced during testing my code and to make it a more organized code.

What AI added to my code

1. Password Change Feature

   • After entering the correct code, the system now asks the user to set a new 4-digit password.

   • The variable waitingForNewCode acts as a flag to know if the next input is a login attempt or a password update.

2. Masked Password Input on LCD

   • Instead of showing the digits, the LCD shows * characters for each entered digit, improving security.

What I learned:

 What is "state management"?

• A state is simply "what situation your system is in right now."

• In my safe door project, the system has two different situations (states):

  1. Normal login mode → waiting for the user to enter the current password.

  2. Password update mode → waiting for the user to enter a new password.

What is a "flag"?

• A flag is a variable (often boolean: true/false) used to signal something about the system’s current state.

• In my code, the flag is:

bool waitingForNewCode = false;

This means:

• false → system is in normal login mode.

• true → system is in password update mode.
  
  

3. Better Separation of Functions

   • Created helper functions:

     • recvCode() → handles password input.

FlowChart: 

Issue:
At first, my LCD display and Bluetooth module were not working together smoothly. Whenever I tried to power everything directly from the Arduino, the LCD would sometimes flicker, and the Bluetooth connection would drop unexpectedly.

Suggestion from a peer:
One of my teammates suggested that instead of powering all components directly from the Arduino’s 5V pin, I should use an external regulated power source and separate the load by using a breadboard power rail. They also advised me to check the baud rate of the Bluetooth module to make sure it matched the Arduino’s Serial communication.

Solution:
I applied this advice by connecting the Bluetooth module and servo motor to a DC-DC step-down converter to stabilize the voltage and reduce the load on the Arduino. I also adjusted the baud rate in the code to ensure stable communication. After that, both the LCD and Bluetooth worked perfectly together without interference. And the LCD alone was connected to the 5V from the Arduino. 

Contribution:
I helped my peers by showing them how to use the I2C scanner to detect the LCD address (0x27) and explained how to modify their code if they had a different module.

How peers helped me:
They helped me identify the power distribution problem and suggested an alternative wiring method that made the whole system more stable.

1. Issue: Power Consumption from Servo and Bluetooth Module

When I first connected the servo motor and HC-05 Bluetooth module directly to the Arduino UNO’s 5V pin, the system became unstable:

• The servo motor jittered or didn’t rotate properly.

• The Bluetooth module disconnected randomly.

• The LCD sometimes flickered due to voltage drops

This happened because the Arduino UNO cannot supply enough current for both the servo (which can draw up to 1A under load) and the Bluetooth module.

2. Solution: Using a DC-DC Step-Down Converter

To solve this, I introduced a DC-DC buck converter:

• Input: 9V (from adapter/battery).

• Output: Regulated 5V for the servo and Bluetooth module.

• Shared the GND of Arduino and external supply to maintain a common reference.

Now, the Arduino only powers the logic components (LCD, internal circuitry), while the high-current devices (servo + Bluetooth) get stable power from the DC-DC module.

3. How I Did Know

• I researched the issue online when I noticed servo vibrations and Bluetooth disconnections.

• I found discussions on Arduino forums and YouTube tutorials, where hobbyists recommended separating servo power and using a buck converter for stable current delivery.

• This was confirmed by datasheets that showed Arduino UNO’s onboard regulator provides only ~500mA max, which isn’t enough for servo + Bluetooth.
  
  

4. Mistakes Others Can Avoid

• Do not power servos directly from Arduino UNO’s 5V pin if the servo is under load; it can reset or damage the board.

• Always use a common ground when using an external power supply with Arduino.

• Check the current requirements of each module before wiring—Bluetooth and servo together exceed what Arduino can supply.

• Test with Wokwi first, but remember simulations don’t show power issues, so always cross-check with datasheets.
  
  

 Final Reflection:
The biggest challenge was power distribution. By pausing, researching, and applying a DC-DC step-down converter, I ensured the system worked reliably without resets or unstable behavior. This step was critical for moving from simulation (Wokwi) to successful real implementation.

This week, I learned how to properly wire and power a servo motor in an Arduino-based system. At first, I connected the servo directly to the Arduino UNO, but I discovered that it caused power instability because the servo requires higher current than the Arduino can supply. By researching and testing, I implemented a DC-DC step-down converter to provide a stable 5V power line for the servo, while keeping a common ground with the Arduino.

In my final project, I will also be using a servo motor as part of the system. The knowledge I gained this week is directly applicable:

• I now know the correct way to wire the servo motor so it operates smoothly without affecting other components.

• I understand the importance of separating power supplies for high-current devices and ensuring a common ground reference.

• I gained confidence in debugging power-related issues, which will save time when building the final project.

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchcell.com%2Felectronics%2Fxl4016e1-buck-converter-module-review-300w-9a&psig=AOvVaw2oscRvyu67s3lS8wkbR6xv&ust=1757944025004000&source=images&cd=vfe&opi=89978449&ved=0CBgQjhxqFwoTCOi2lfux2I8DFQAAAAAdAAAAABAE

The coolest thing I learned this week was how to build and program a robotic arm. I was really interested in working on this project because it combined mechanical design, electronics, and coding in a practical way. Seeing the robotic arm respond to our inputs and perform tasks was not only exciting but also showed me how different engineering skills can come together in one system.

Another thing that I will never forget from this week is that our team became the Winner of the Hackathon. This achievement meant a lot to me because it validated the effort and creativity we put into the project. It also boosted my confidence in my ability to work in a team, solve problems under time pressure, and apply my engineering knowledge in a competitive environment