im doing one of your project https://www.hackster.io/47551/build-a-tank-volume-reader-in-under-30-using-esp32-076faa , i have followed all the instructions and then i have a problem , the esp cannot send the data to ubidot, even though i can upload the code and i can see the result in serial monitor (i haven’t put all the sensor) as you can see below , can you help me?
Dear @vindobangun,
The values are not being sent because the temperature & humidity sensor readings are not being taken properly. Please verify the connection between your sensor and the module until the output sensor show the real value.
Then, once you are able to receive the real value instead of nan, you will receive the values properly in the Ubidots side.
I hope this would help you!
All the best,
Maria C.
do i need to create device esp 32 in ubidots? i have tried testing Ubidots MQTT broker using MQTTlens
and it didn’t success
Are you modifying the structure of the payload after commented those lines of code? Probably the payload is being built wrong. For this, I recommend you un-comment this line of code in order to check the structure of the payload.
Please reference to the Ubidots MQTT documentation to review how the payload should be structured.
To start with Ubidots using MQTT Lens, check the video below:
All the best,
Maria C.
i didn’t modify the structure , i just commented all the code that consisted of dht
#include <WiFi.h>
#include <PubSubClient.h>
//#include <DHT.h>
/****************************************
* Define Constants
****************************************/
namespace {
const char * WIFISSID = ""; // Put your WifiSSID here
const char * PASSWORD = ""; // Put your wifi password here
const char * TOKEN = ""; // Put your Ubidots' TOKEN
const char * MQTT_CLIENT_NAME = "KzSf1iZsOv"; // MQTT client Name, please enter your own 8-12 alphanumeric character ASCII string;
const char * VARIABLE_LABEL_1 = "distance"; // Assign the variable label
const char * VARIABLE_LABEL_2 = "humidity"; // Assign the variable label
const char * VARIABLE_LABEL_3 = "temperature"; // Assign the variable label
const char * DEVICE_LABEL = "tugaskp"; // Assign the device label
const char * MQTT_BROKER = "things.ubidots.com";
//const int DHTPIN = 33; // Pin where is connected the DHT11
// const int DHTTYPE = DHT11; // Type of DHT
const int trigPin = 13; // Triger pin of the HC-SR04
const int echoPin = 14; // Echo pin of the HC-SR04
}
/* Sensor's declarations */
long duration;
float distance;
/* Space to store the request */
char payload[300];
char topic[150];
/* Space to store values to send */
char str_sensor[10];
//char str_TempSensor[10];
//char str_HumSensor[10];
/****************************************
* Auxiliar Functions
****************************************/
WiFiClient ubidots;
PubSubClient client(ubidots);
//DHT dht(DHTPIN, DHTTYPE);
void callback(char* topic, byte* payload, unsigned int length) {
char p[length + 1];
memcpy(p, payload, length);
p[length] = NULL;
String message(p);
Serial.write(payload, length);
Serial.println(topic);
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.println("Attempting MQTT connection...");
// Attemp to connect
if (client.connect(MQTT_CLIENT_NAME, TOKEN, "")) {
Serial.println("Connected");
} else {
Serial.print("Failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 2 seconds");
// Wait 2 seconds before retrying
delay(2000);
}
}
}
/****************************************
* Sensor Functions
****************************************/
float readDistance() {
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = (pulseIn(echoPin, HIGH));
distance = float(duration/29/2);
return distance;
}
/****************************************
* Main Functions
****************************************/
void setup() {
Serial.begin(115200);
WiFi.begin(WIFISSID, PASSWORD);
/* Initializing the DHT11 */
// dht.begin();
/* Assign the PINS as INPUT/OUTPUT */
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
Serial.println();
Serial.print("Wait for WiFi...");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(500);
}
Serial.println("");
Serial.println("WiFi Connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
client.setServer(MQTT_BROKER, 1883);
client.setCallback(callback);
}
void loop() {
if (!client.connected()) {
reconnect();
}
/* Reading temperature and humidity */
// float humidity = dht.readHumidity();
//float temperature = dht.readTemperature();
/* call the funtion readDistance() */
distance = readDistance();
/* 4 is mininum width, 2 is precision; float value is copied onto str_sensor*/
dtostrf(distance, 4, 2, str_sensor);
//dtostrf(humidity, 4, 2, str_HumSensor);
//dtostrf(temperature, 4, 2, str_TempSensor);
/* Building the Ubidots request */
sprintf(topic, "%s%s", "/v1.6/devices/", DEVICE_LABEL);
sprintf(payload, "%s", ""); // Cleans the payload
sprintf(payload, "{\"%s\": %s,", VARIABLE_LABEL_1, str_sensor); // Adds the variable label
// sprintf(payload, "%s\"%s\": %s,", payload, VARIABLE_LABEL_2, str_HumSensor); // Adds the variable label
//sprintf(payload, "%s\"%s\": %s}", payload, VARIABLE_LABEL_3, str_TempSensor); // Adds the variable label
sprintf(payload, "%s {\"value\": %s}}", payload, str_sensor);
/* Print the sensor reading to the Serial Monitor */
Serial.println("Publishing values to Ubidots Cloud");
Serial.print("Distance = ");
Serial.println(distance);
// Serial.print("Humidity = ");
// Serial.println(humidity);
//Serial.print("Temperature = ");
//Serial.println(temperature);
/* Publish the request to Ubidots */
client.publish(topic, payload);
client.loop();
delay(1000);
}it works right now thank you , i changed the payload
sprintf(payload, "{\"%s\": %s}", VARIABLE_LABEL_1, str_sensor);
I’m glad to read that! 
All the best,
Maria C.
i have a question , can you explain me about volume formula ? how did you find the formula?