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Background of the idea ​

In Japan, there has been an increase in the number of random stabbings recently. People who have nothing to do with the incident are being stabbed unexpectedly and it is making the news. Even if I think about it by replacing myself with the person who was stabbed, I feel uneasy that it cannot be prevented. This is because people can only recognize what is in front of them, and the range of what they can recognize is only 200 degrees, so there is a large blind spot behind them.

When I was thinking about whether there was a good solution, I found a good solution in the main character of the manga Golgo 13. The manga Golgo 13 is a manga that has been recognized by the Guinness World Records as having the largest number of publications for a single manga series in the world, with 201 volumes.

The main character in the manga 'Golgo 13' is a top-class sniper with the code name 'Golgo 13', whose real name is unknown. He boasts a success rate of almost 100% not only in sniping, but also in hand-to-hand combat and sabotage, but despite his stern appearance, he is actually a very cautious person who could even be called a coward. Because of his cowardice, he never lets anyone stand behind him. Here was the hint.

In other words, if I can detect and repel others behind me like Golgo 13, the problem will be solved.

Never stand behind me.

Golgo 13 Machine ​

The name of my final project is the Golgo 13 Machine. It is a machine that monitors the area behind it with a millimeter wave radar sensor and alerts you when someone approaches.

Final Project Sketch1

Final Project Sketch2

3D model ​

3D model created with Fusion.

3D model Download

Animation of 3D models ​

Animation of 3D models created in Fusion.

Requirement Definition ​

Purpose ​

To detect a person approaching from behind using a millimeter-wave radar sensor, and to alert the user via vibration and smartphone notification.

Functional Requirements ​

1. Millimeter-Wave Detection ​

• The system shall detect objects or people approaching from behind using a millimeter-wave radar sensor.
• Detection range should cover at least 1–2 meters behind the user.

2. Microcontroller Control (XIAO RP2040) ​

• The microcontroller shall receive and process distance data from the radar sensor.
• It shall determine if the threshold distance is breached.

3. Vibration Alert ​

• If someone is detected within the danger zone, the device shall activate a vibration motor.
• Vibration intensity may be fixed or adjustable.

4. Smartphone Notification ​

• The system shall send a wireless alert to the user’s smartphone when detection is triggered.
• BLE (Bluetooth Low Energy) is preferred for real-time communication.
• The notification should include a simple "Alert: Person approaching from behind" message.

5. Optional Features (Future Enhancements) ​

• Adjustable sensitivity or detection range via smartphone app
• Sound alert in addition to vibration

Hardware Summary ​

• XIAO ESP32C3
• Millimeter-wave radar sensor
• Vibration motor
• BLE module (or use built-in if available)
• Battery pack

System diagram ​

The following image shows an overview of the system.

Sequence diagram ​

The following images visually represent the flow of system processing.

Development Task List ​

1. Requirement Definition and System Design ​

• Clarify the purpose and functional requirements for detecting a person approaching from behind
• Create a system block diagram and a sequence diagram

2. Hardware Selection and Preparation ​

• Select and prepare the XIAO ESP32C3 microcontroller board
• Select and connect a millimeter-wave radar sensor
• Select and connect a vibration motor
• Select and connect a BLE module (including the use of built-in functions if available)
• Select a battery pack and design the power supply system

3. Software Development ​

• Acquire and analyze data from the millimeter-wave radar sensor
• Control the vibration motor when a threshold is exceeded
• Implement smartphone notification via BLE communication
• Integrate and validate the full system operation

4. Case Design and Fabrication ​

• Design the enclosure using 3D modeling software (e.g., Fusion 360)
• Fabricate the enclosure using a 3D printer or CNC router
• Design the layout and mounting method for internal components

5. System Integration and Testing ​

• Integrate hardware and software
• Verify the operation of each component and perform debugging
• Test and adjust the system in real usage conditions

6. Documentation and Submission Preparation ​

• Document the project overview, design drawings, circuit diagrams, and source code
• Take and edit photos and videos of the project
• Create a final presentation slide deck and a 1-minute demo video
• Organize and prepare all required files and materials for submission

Development Schedule ​

Schedule (May 10 – June 6) ​

System integration ​

System integration was carried out in Week 15.
For details, please refer to the Week 15 page.

1. PCB Design ​

To enable system integration, I designed a custom PCB using Fusion 360 tailored to the final project.
The board includes headers for connecting sensors, power input, and communication pins.

Design Process ​

1. Circuit Schematic Design
   I first created a circuit schematic in Fusion 360 and placed key components such as:

• ESP32-C3 microcontroller
• 24GHz motion detection / Doppler radar sensor module
• Transistors
• Resistors and capacitors
• Pin headers for external motor connection

2. PCB Layout
   After completing the schematic, I moved on to the PCB layout.

• I routed the traces carefully to avoid interference.
• I added mounting holes to match the design of the enclosure.

3. Exporting PNG Files
   To fabricate the PCB using a CNC milling machine, I exported the following files:

• traces.png: for milling copper traces
• millholes.png: for drilling component holes
• outline.png: for cutting the board outline

2. Enclosure Design ​

I modified the 3D model created in week02 to accommodate the PCB.

3. Integration of PCB and Enclosure ​

• Imported the 3D model of the PCB into the Fusion 360 enclosure design and aligned it for a perfect fit.
• Adjusted mounting holes and support structures based on the PCB dimensions and connector positions.

Bill of Materials (BOM) ​

Slide ​

Video ​