DIY Smart Ultrasonic Parking Sensor

Build your own parking sensor to help you park and tie into your smart home to trigger automation actions.

Here’s the sketch, or you can download it from github.

// All of the following includes are for WIFI
#include <ESP8266WiFi.h>          //ESP8266 Core WiFi Library (you most likely already have this in your sketch)
#include <WiFiManager.h>         // https://github.com/tzapu/WiFiManager

// MQTT IOT Includes
#include <PubSubClient.h>

//ultrasonic library https://github.com/Martinsos/arduino-lib-hc-sr04
#include <HCSR04.h>

// defines pins numbers
const int trigPin = D2;  //D2
const int echoPin = D1;  //D1
const int greenPin = D5; //D4
const int redPin = D4; //D5

//
UltraSonicDistanceSensor distanceSensor(trigPin, echoPin);

// defines variables
double last_dist, cur_dist;

// wifi config
// wifi auto configs using wifi manager. Just boot the device, then connect to the "ParkingSensorSetup" network
// after connecting, if you're not automatically redirected go to http://192.168.4.1 in your web browser.

// MQTT config
#define MQTT_SERV "192.168.50.167"
#define MQTT_PORT 1883
#define MQTT_NAME "YOUR MQTT USER"
#define MQTT_PASS "YOUR MQTT PASS"
#define MQTT_TOPIC "stat/garagebay1/parking"

WiFiClient client;
PubSubClient pubclient(MQTT_SERV, MQTT_PORT, client);

String macToStr(const uint8_t* mac)
{
  String result;
  for (int i = 0; i < 6; ++i) {
    result += String(mac[i], 16);
    if (i < 5)
      result += ':';
  }
  return result;
}

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT); // Sets the echoPin as an Input
  Serial.begin(115200); // Starts the serial communication

  //Connect to WiFi
  Serial.print("\n\nConnecting Wifi... ");
  WiFiManager wifiManager;
  wifiManager.autoConnect("ParkingSensorSetup");

  Serial.println("Wifi Connected!");
  
  pinMode(greenPin, OUTPUT);     // Initialize the LED_BUILTIN pin as an output
  pinMode(redPin, OUTPUT);     // Initialize the LED_BUILTIN pin as an output
  digitalWrite(greenPin, LOW);
  digitalWrite(redPin, HIGH);

}

void loop() {
  MQTT_connect();
  
  cur_dist = distanceSensor.measureDistanceCm();

  Serial.print(cur_dist);
  Serial.print("cm");
  Serial.println();

  
  if(cur_dist < 140.00  && last_dist >= 140.00){
    digitalWrite(greenPin, LOW);
    digitalWrite(redPin, HIGH);
    pubclient.publish(MQTT_TOPIC, "PARKED");
    Serial.println("Publish: PARKED");
  }

  if(cur_dist >= 140.00  && last_dist < 140.00){
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, HIGH);
    pubclient.publish(MQTT_TOPIC, "VACANT");
    Serial.println("Publish: VACANT");
  }

  last_dist = cur_dist;
  
  delay(500);
}

/***************************************************
  Adafruit MQTT Library ESP8266 Example

  Must use ESP8266 Arduino from:
    https://github.com/esp8266/Arduino

  Works great with Adafruit's Huzzah ESP board & Feather
  ----> https://www.adafruit.com/product/2471
  ----> https://www.adafruit.com/products/2821

  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing
  products from Adafruit!

  Written by Tony DiCola for Adafruit Industries.
  MIT license, all text above must be included in any redistribution
 ****************************************************/

void MQTT_connect() 
{
  // Stop if already connected.
  if (pubclient.connected()) 
  {
    return;
  }

  Serial.print("Connecting to MQTT... ");

  // Generate client name based on MAC address and last 8 bits of microsecond counter
  String clientName;
  clientName += "esp8266-";
  uint8_t mac[6];
  WiFi.macAddress(mac);
  clientName += macToStr(mac);
  clientName += "-";
  clientName += String(micros() & 0xff, 16);

  Serial.print("Connecting to ");
  Serial.print(MQTT_SERV);
  Serial.print(" as ");
  Serial.println(clientName);
  
  if (pubclient.connect((char*) clientName.c_str(), MQTT_NAME, MQTT_PASS)) {
    Serial.println("Connected to MQTT broker");
    Serial.print("Topic is: ");
    Serial.println(MQTT_TOPIC);
  }
  else {
    Serial.println("MQTT connect failed");
    Serial.println("Will reset and try again...");
    abort();
  }

  //uint8_t retries = 3;
  //while ((ret = mqtt.connect()) != 0) // connect will return 0 for connected
  //{ 
  //     Serial.println(mqtt.connectErrorString(ret));
  //     Serial.println("Retrying MQTT connection in 5 seconds...");
  //     mqtt.disconnect();
  //     delay(5000);  // wait 5 seconds
  //     retries--;
  //     if (retries == 0) 
  //     {
  //       // basically die and wait for WDT to reset me
  //       while (1);
  //     }
  // }
  Serial.println("MQTT Connected!");

  
}

And here’s the schematic: