Smart parking bay

Why it’s here

Move from clear to caution to stop; check the phone occupancy status.

How it works

Combine ranging, traffic lights and a Wi-Fi occupancy page. 15 cm selects red; 30 cm selects amber. Above 30 cm is green and the bay is free. This guided model targets the original ESP32 and Arduino-ESP32 3.x; radio, acoustics, loads and mechanics are simplified.

Try it

1. Open this experiment
2. Move from clear to caution to stop; check the phone occupancy status.

Connections

• GPIO 5 / 19 — TRIG / ECHO
• GPIO 25 / 26 / 27 — Red / amber / green through resistors
• Wi-Fi — HTTP parking status

Example sketch

#include <WiFi.h>
#include <WebServer.h>
WebServer server(80);
bool lightOn = false;
float distanceCm = -1;

void setup() {
  pinMode(5, OUTPUT); pinMode(19, INPUT);
  for (int pin : {25, 26, 27}) pinMode(pin, OUTPUT);
  WiFi.begin("YOUR_SSID", "YOUR_PASSWORD");
  while (WiFi.status() != WL_CONNECTED) delay(250);
  server.on("/", []() { server.send(200, "text/plain", distanceCm < 0 ? "UNKNOWN" : distanceCm <= 30 ? "TAKEN" : "FREE"); });
  server.begin();
}

void loop() {
  digitalWrite(5, LOW); delayMicroseconds(2);
  digitalWrite(5, HIGH); delayMicroseconds(10);
  digitalWrite(5, LOW);
  unsigned long echo = pulseIn(19, HIGH, 30000);
  float cm = echo ? echo / 58.0f : -1;
  distanceCm = cm;
  digitalWrite(25, cm >= 0 && cm <= 15);
  digitalWrite(26, cm > 15 && cm <= 30);
  digitalWrite(27, cm > 30);
  server.handleClient(); delay(50);
}

Check your understanding

What happens exactly at 15 cm and 30 cm?