🔗 Phase 4: Integration & Testing

I wired all components inside my custom PLA enclosure. Each cable was crimped to match the headers on my single-sided PCB, which I milled on a Maker Carvera by removing all copper except the traces. Once connected, the system follows a strict flow to ensure safe operation:

4.1 System Flow

1. Idle: Relay open → machine powerless. LCD shows “Waiting for user…”, all LEDs off.
2. Authenticate: LCD prompts “Place Finger” (up to 5 attempts). The R307 sensor delivers >99% valid read rate (FAR <0.001%, FRR <1%).
3. Grant access: On valid scan → relay closes (power enabled), green LED lights, LCD displays a 10-minute countdown in seconds (critical for user awareness).
4. Failures: Each bad scan increments a counter. After 3 consecutive failures → relay remains open, red & yellow LEDs flash, buzzer sounds, LCD shows “Access Denied.”
5. Suspend mode: If 5 attempts elapse without unlock → low-power suspend (relay open, yellow LED steady, LCD “Standby – Press Emergency to Retry”). Pressing the emergency button resets the flow.
6. Emergency stop: Pressing the emergency button at any time immediately opens relay, triggers buzzer, LCD “EMERGENCY LOCKOUT,” red LED on. After 30 s, normal startup resumes.

4.2 Assembly & Visuals

4.3 Step-by-Step Assembly

1. PCB Milling: I milled a single-sided PCB on the Maker Carvera, carving away all unwanted copper to leave only the traces.

   

2. Enclosure Printing: I 3D-printed the case in PLA, test-fitted the PCB and filed openings for each component.

   

3. Cable Crimping: I cut color-coded wires to length, stripped insulation, and crimped Dupont terminals.
4. Module Mounting: I pressed the fingerprint sensor, emergency button, LCD, LEDs and buzzer into their slots until flush.
5. Wiring: I routed cables through designated slots, secured them with zip-ties, and kept power and signal lines separated.
6. PCB Installation: I placed the populated PCB in the case and fastened it with M3 screws and stand-offs.
7. Final Connections: I plugged each connector onto its header, verifying orientation against silkscreen labels.
8. Case Closure: I closed the lid carefully, ensured no wires were pinched, and tightened all screws.
9. Bench Testing: I powered on the system, confirmed “Waiting for user…” on the LCD, tested valid/invalid scans and the emergency stop.
10. Machine Integration: I mounted the sealed case onto the saw, connected the relay output to the saw’s power circuit, secured cables, and performed a full operational test.

    

4.4 Testing & Validation

As part of my Fab Academy evaluation, I conducted stress tests:

• ≈500 fingerprint scans over several hours → no false accepts, <1% false rejects.
• 50 emergency-stop activations → relay and buzzer responded within <10 ms each.
• Cooldown logic kept sensor temperature within safe limits throughout testing.

Pressing the emergency button instantly disables the relay, triggers a 30 s lockout, and lights the red LED. Unauthorized access activates buzzer + red LED and enforces a cooldown period before retry.

✅ Phase 5: Final Deployment & Validation

The final version was tested in the actual FabLab where the bench saw is located. A real session simulated a workshop environment:

• Unregistered users were denied access
• Registered fingerprints granted 10-minute machine control
• System safely locked and required reset via button after time expired

Everything was documented, including schematics, code, 3D files, and test logs. Final adjustments included mounting the system to a protective frame, polishing the acrylic display cover, and labeling ports.

🔍 Final Conclusions

• Modular Design: Headers and custom cables make this system scalable and maintainable.
• Safety First: Cooldown logic and emergency overrides ensure no unsafe operation is possible.
• Admin/Operation Split: Makes management intuitive while keeping runtime logic lightweight.
• Real-World Proof: Tested successfully in a real FabLab with real tools and people.
• Future Upgrades: Ready for Telegram/MQTT integration, RTC logging, and improved interfaces.

This project shows how open-source tools and careful planning can lead to powerful safety systems built by students for real-world use.

FabSafe by Jhonatan Cortes is licensed under CC BY-NC-SA 4.0 International .