IoT Parking Slot Availability Display using Ultrasonic Sensors

Drivers circling a lot looking for a free slot waste fuel and time, while lot operators have no live picture of occupancy. An ultrasonic sensor aimed at each slot answers the question directly: a short echo means a car is there. The engineering work is in polling several sensors without crosstalk, the occupied/free threshold and the live display. This project builds a student-scale IoT parking monitor on an ESP32: three demo slots each get an HC-SR04 ultrasonic sensor on a post, the ESP32 polls them in sequence, an LCD shows the free-slot count, a green/red LED per slot shows its state, and the slot map publishes to a phone dashboard over Wi-Fi.

1. The ESP32 triggers each HC-SR04 in turn and measures the echo time, converting it to distance for that slot.
2. Each distance is compared against the calibrated occupied threshold; readings below it mark the slot occupied, above it free.
3. A debounce count requires the state to persist across several polls before it flips, so a walking person doesn't toggle a slot.
4. The LCD updates with the free-slot count and per-slot states, and the post LEDs switch green or red to match.
5. On every state change (and a periodic heartbeat) the ESP32 publishes the slot map to the phone dashboard over Wi-Fi.
6. The buyer runs the included calibration procedure once to set the threshold for their exact demo geometry.

Tech stack:

• ESP32 development board
• HC-SR04 ultrasonic sensors (one per slot)
• 16x2 character LCD
• Green/red LED indicators
• Blynk-style IoT dashboard (phone slot map)
• Arduino IDE (C/C++ firmware)
• 5 V regulated power supply

• [Per-slot ultrasonic sensing] Each demo slot has its own HC-SR04 sensor measuring the distance to whatever is parked there.
• [Occupied/free threshold logic] Firmware compares each reading against a calibrated distance threshold to decide the slot state, with debouncing against passing movement.
• [LCD availability display] A 16x2 LCD shows the number of free slots and the per-slot status at a glance.
• [Per-slot LED indicators] A green/red LED pair at each slot post mirrors its state for the demo audience.
• [Wi-Fi slot map] The ESP32 publishes the live slot map to a phone dashboard over Wi-Fi for remote checking.
• [Sequential sensor polling] Sensors are polled one at a time in firmware to avoid ultrasonic crosstalk between adjacent posts.
• [Threshold calibration procedure] A buyer-run procedure sets the occupied distance for the demo geometry, documented in the report.

• Working model parking lot with three ultrasonic sensor posts, ESP32, LCD and LEDs
• Complete firmware with commented polling, threshold and telemetry logic
• Phone dashboard setup guide with screenshots
• Threshold calibration procedure
• Wiring diagram and connection table
• Project report PDF (background, system design, firmware logic, IoT architecture)
• PPT presentation for final review
• Viva Q&A preparation document (ultrasonic sensing, ESP32, threshold logic, IoT dashboards)

• The demo covers three model slots — a real lot would need one sensor per slot plus weatherproofing and power distribution, which is outside the student scope.
• Ultrasonic readings are affected by temperature, angled surfaces and soft materials; the threshold is tuned for the demo geometry, not universal.
• Detection latency and accuracy are design targets verified on the buyer's own build; no certified figures are claimed.
• Wi-Fi dashboard updates depend on the buyer's own network and the third-party service; no uptime is guaranteed for external services.
• The system reports occupancy only — it cannot identify vehicles or enforce reservations.
• Battery or solar operation is not included; the unit runs on a 5 V adapter.