My Open-Source Garage Parking Sensor

Built a parking guide that shows a colored LED bar indicating how far the car is from the wall. Hardware: ESP32, HC-SR04 ultrasonic sensor, and a 10-LED bar graph module.

The LED mapping: green LEDs illuminate from 200cm down to 60cm as you approach. At 60cm, yellow LEDs warn. Below 30cm, red LEDs flash. Below 15cm, all LEDs flash rapidly — stop immediately. The thresholds are stored in flash and configurable via a simple web interface hosted on the ESP32.

One reliability improvement: the HC-SR04 occasionally outputs erroneous readings (spikes to zero or maximum range). I apply a median filter over 5 consecutive readings and discard any reading that differs from the median by more than 10cm. This eliminates the occasional flash from a bad echo.