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--- pm:prj2026:bianca.popa1106:ana.stanciulescu [2026/05/16 23:06]
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+++ pm:prj2026:bianca.popa1106:ana.stanciulescu [2026/05/25 01:42] (current)
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 | 3× RGB LEDs (CC)    | Optical indicator for each sensor (Green = Safe, Red = Stop) |  |
 | 6x Resistor   | A separate 220Ω resistor was used in series with the anode of each RGB LED |  |
-| Passive Buzzer   | Variable sound alarm   |  [[https://www.alldatasheet.com/datasheet-pdf/pdf/1284499/JOY-IT/KY-006.html|Buzzer]] |
+| Passive Buzzer   | Variable sound alarm   | [[https://www.alldatasheet.com/datasheet-pdf/pdf/1284499/JOY-IT/KY-006.html|Buzzer]] |
 | LCD 16×2  | Displays measured distances   | [[https://www.datasheetcafe.com/JHD162A-pdf-14977/|LCD 16×2]] |
@@ Line 113: / Line 113: @@
 ===== Results =====
-The system achieves an accuracy of approximately 1–2 cm. The interface is intuitive, allowing the driver to quickly identify which part of the car is closest to an obstacle.
+The completed system was mounted on a toy car and powered by a portable USB
+power bank, making it fully self-contained and independent of a development
+computer.
+The three ultrasonic sensors achieve a ranging accuracy of approximately
+-2 cm across their effective operating range. The exponential moving average
+filter applied to each sensor's readings eliminates the characteristic
++/-1-2 cm jitter of the raw HC-SR04 output, producing stable distance values
+without introducing perceptible lag (the system reacts to a real distance
+change in under ~600 ms).
+The three-zone feedback proved intuitive: each RGB LED independently reflects
+the proximity state of its corresponding sensor (green / yellow / red),
+letting the driver instantly identify which side of the vehicle is closest to
+an obstacle. The buzzer, driven by the minimum of the three measured
+distances, varies both its beep cadence and its tone frequency continuously
+as the nearest obstacle approaches, culminating in a continuous tone below
+cm. The LCD provides a precise numeric readout of all three distances
+simultaneously, for drivers who prefer a "dashboard" view.
+The asymmetric hysteresis on the LED state machine eliminated the boundary
+flickering observed in early prototypes, and the non-blocking architecture
+keeps the buzzer responsive even while the sensors are being polled.
+A demonstration of the complete system in operation:
+[[https://youtube.com/shorts/_dmrASQBtu4|Watch here]]
 ===== Conclusions =====
-The implementation on the ATmega328P demonstrates efficient handling of multiple sensors simultaneously using interrupts and timers. The project is scalable and can be integrated into any small vehicle.
+Building this project taught me a lot about how embedded systems work in
+practice - not just coding, but also designing the hardware, debugging odd
+issues, and getting everything to run smoothly on a moving toy car.
+One of the biggest lessons was learning how limited hardware resources have
+to be shared carefully. The ATmega328P only has three timers, and I needed
+them for the buzzer, LEDs, and time measurements at the same time. I ran
+into conflicts where the LEDs flickered whenever the buzzer was active, which
+forced me to better understand how the timers and pins are connected. In the
+end, I simplified the LEDs to basic on/off colors to avoid those conflicts.
+I also learned how important pin selection is. At one point I connected a
+sensor to PB5, not realizing it was also used by the programmer. That caused
+upload failures until I rewired the sensor, and after that I became much more
+careful about checking pin functions beforehand.
+Another challenge was dealing with noisy sensor readings. The measured
+distance constantly shifted by small amounts, which made the LEDs flicker and
+the buzzer react unpredictably. Adding a simple averaging filter and some
+hysteresis made the whole system feel much more stable and reliable.
+Writing the I2C LCD driver and interrupt handlers from scratch also gave me a
+much better understanding of what happens behind the scenes, compared to just
+using ready-made libraries.
+If I continued developing the project, I would add a low-power sleep mode,
+improve the LED fading effects, and possibly include more sensors for better
+coverage around the car.
+Overall, the project showed that the ATmega328P can reliably handle multiple
+sensors and peripherals at once using timers and interrupts, while the
+modular structure makes the system easy to adapt for other small vehicles.