Keisar
1
Hi,
I was using a bme280 to read exterior temperature and humidity but after a month a very humid period the sensor died.
To replace it I get a SHT20 sensor supposed to be for exterior/soil and modified the program.
It run very nicely for a little while and then after few hours the temperature goes crazy:
Then I reboot the Arduino and temperatures goes immediately right.
Humidity is fine.
It's like the temperature suddently have an offset of smth like 50 degrees.
No external factor.
Any clue why ?
Sensor model
Thanks.
Here the code I use for this sensor (an extract from the code) :
#include <Wire.h>
#include "DFRobot_SHT20.h"
DFRobot_SHT20 sht20;
float humd ;
float temp ;
void setup()
{
sht20.initSHT20(); // Init SHT20 Sensor
delay(100);
sht20.checkSHT20(); // Check SHT20 Sensor
}
void loop()
{
humd = sht20.readHumidity(); // Read Humidity
temp = sht20.readTemperature(); // Read Temperature
delay(1000);
}
stevemj
2
If you read the device's reviews it would seem many go wrong 
b707
3
@Keisar
Problems may be in the part of the code that you did not show, so always post the full code
Keisar
4
Okay, here it is :
/************************* Library ***************************/
#include <SPI.h>
#include "Adafruit_MQTT_Client.h"
#include <Ethernet.h>
//#include <Adafruit_BME280.h>
#include <SD.h>
#include "DFRobot_SHT20.h"
#include <Wire.h>
/************************* Ethernet Client Setup *****************************/
byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xEC};
IPAddress myDns(192, 168, 1, 1);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
/************************* SD *********************************/
const int chipSelect = 4;
/************************* MQTT brokers *********************************/
#define Local_SERVER "192.168.1.65"
#define Local_SERVERPORT 1883
#define Local_USERNAME "xxxxxxx"
#define Local_KEY "xxxxxxx"
#define AIO_SERVER "io.adafruit.com"
#define AIO_SERVERPORT 1883
#define AIO_USERNAME "xxxxxxxx"
#define AIO_KEY "xxxxxxxx"
/************************* Time global *********************************/
unsigned long action_AIO = 0;
unsigned long action_Local = 0;
unsigned long action_SD = 0;
#define intervale_publication_AIO 10000 //Interval de publication sur le réseau internet
#define intervale_publication_Local 5000 //Interval de publication sur le réseau local
#define intervale_publication_SD 1800000 //Interval de publication sur la carte SD
unsigned long temps = 0;
/************************* Array & tests *********************************/
#define interval_array 3600000 // Time between update of each value
#define interval_update_array 5000 // Time between each update of the same value of the array
#define size_array 10 // Number of value of the array
long time_array = 0 ;
long time_update =0 ;
byte index = 1 ;
float temp_max_tempo ;
float temp_min_tempo ;
float array_max [size_array];
float array_min [size_array];
float temperature_loop ;
float global_max_val ;
float global_min_val ;
/************ Global State ******************/
//Set up the ethernet client
EthernetClient client;
EthernetClient client2;
Adafruit_MQTT_Client mqtt_Local(&client, Local_SERVER, Local_SERVERPORT, Local_USERNAME, Local_KEY);
Adafruit_MQTT_Client mqtt_AIO(&client2, AIO_SERVER, AIO_SERVERPORT, AIO_USERNAME, AIO_KEY);
// You don't need to change anything below this line!
#define halt(s) { Serial.println(F( s )); while(1); }
/************************* Input Setup *********************************/
//#define adresseI2CduBME280 0x76
//Adafruit_BME280 bme;
//unsigned long action = 0;
DFRobot_SHT20 sht20;
/****************************** Feeds ***************************************/
Adafruit_MQTT_Publish Local_publi_temperature = Adafruit_MQTT_Publish(&mqtt_Local, Local_USERNAME "/feeds/temperature");
Adafruit_MQTT_Publish Local_publi_humidite = Adafruit_MQTT_Publish(&mqtt_Local, Local_USERNAME "/feeds/humidite");
Adafruit_MQTT_Publish Local_publi_max_temp = Adafruit_MQTT_Publish(&mqtt_Local, Local_USERNAME "/feeds/max_temp");
Adafruit_MQTT_Publish Local_publi_min_temp = Adafruit_MQTT_Publish(&mqtt_Local, Local_USERNAME "/feeds/min_temp");
Adafruit_MQTT_Publish AIO_publi_temperature = Adafruit_MQTT_Publish(&mqtt_AIO, AIO_USERNAME "/feeds/temperature");
Adafruit_MQTT_Publish AIO_publi_humidite = Adafruit_MQTT_Publish(&mqtt_AIO, AIO_USERNAME "/feeds/humidite");
Adafruit_MQTT_Publish AIO_publi_max_temp = Adafruit_MQTT_Publish(&mqtt_AIO, AIO_USERNAME "/feeds/max_temp_2");
Adafruit_MQTT_Publish AIO_publi_min_temp = Adafruit_MQTT_Publish(&mqtt_AIO, AIO_USERNAME "/feeds/min_temp");
/*------------------------------------ Setup ------------------------------------*/
void setup()
{
Serial.begin(9600);
Serial.println(F("Debut programme"));
Serial.print(F("\nInit the Client..."));
Ethernet.begin(mac);
delay(500); //give the ethernet time to initialize
//bme.begin(adresseI2CduBME280);
sht20.initSHT20();
delay(100);
sht20.checkSHT20();
temp_min_tempo = sht20.readTemperature() ;
temp_max_tempo = sht20.readTemperature() ;
temp_min_tempo = sht20.readTemperature() ;
temp_max_tempo = sht20.readTemperature() ;
global_max_val = sht20.readTemperature() ;
global_min_val = sht20.readTemperature() ;
for (int i=0; i < size_array; i++)
{
array_max [i] = sht20.readTemperature();
array_min [i] = sht20.readTemperature();
}
if (!SD.begin(chipSelect))
{
Serial.println("Card failed, or not present");
return;
}
Serial.println(F("Setup all good"));
}
/*------------------------------------ Loop ------------------------------------*/
void loop()
{
temps = millis();
temperature_loop = sht20.readTemperature();
global_max_val = -1000;
global_min_val = 1000;
MQTT_AIO_connect() ;
MQTT_Local_connect() ;
if((millis() - time_update) > interval_update_array) // Update of the current array position if temperature > / <
{
//Serial.print("Check value #");Serial.println(index);
if (temp_max_tempo < temperature_loop)
{
array_max[index] = temperature_loop;
temp_max_tempo = temperature_loop;
//Serial.println("UPDATE");
}
if (temp_min_tempo > temperature_loop)
{
array_min[index] = temperature_loop;
temp_min_tempo = temperature_loop;
}
for (int i=0; i < size_array; i++) // Check what is the biggest vallue in both array
{
if (array_max[i] > global_max_val)
{
global_max_val=array_max[i];
}
if (array_min[i] < global_min_val)
{
global_min_val=array_min[i];
}
}
time_update = millis();
}
if((millis() - time_array) > interval_array) //Switch of array position and reset of old values
{
index = index + 1;
if(index >= size_array)
{
index = 0 ;
}
temp_max_tempo = temperature_loop; ;
temp_min_tempo = temperature_loop; ;
array_max[index] = temperature_loop;
array_min[index] = temperature_loop;
time_array = millis();
/*Serial.println("");
Serial.println("Array maximum : ");
for (int i=0; i < size_array; i++)
{
Serial.print(" - ");
Serial.print("Value :");
Serial.print(i);
Serial.print(" : ");
Serial.print(array_max[i]);
if (i == size_array-1){Serial.println("");}
}
Serial.print("Maximum value is : ");Serial.println(global_max_val);
Serial.println("");
Serial.println("Array minimum : ");
for (int i=0; i < size_array; i++)
{
Serial.print(" - ");
Serial.print("Value :");
Serial.print(i);
Serial.print(" : ");
Serial.print(array_min[i]);
if (i == size_array-1){Serial.println("");}
}
Serial.print("Minimum value is : ");Serial.println(global_min_val);
Serial.println("");*/
}
if ( ( temps - action_Local ) > intervale_publication_Local ) //Publication toutes les x secondes sur le MQTT Local
{
action_Local = temps ;
Local_publi_temperature.publish(sht20.readTemperature()) ;
Local_publi_humidite.publish(sht20.readHumidity()) ;
Local_publi_max_temp.publish((float)global_max_val);
Local_publi_min_temp.publish((float)global_min_val);
}
if ( ( temps - action_AIO ) > intervale_publication_AIO ) //Publication toutes les x secondes sur le MQTT Internet
{
action_AIO = temps;
AIO_publi_temperature.publish(sht20.readTemperature()) ;
AIO_publi_humidite.publish(sht20.readHumidity()) ;
AIO_publi_max_temp.publish((float)global_max_val);
AIO_publi_min_temp.publish((float)global_min_val);
}
if ( ( temps - action_SD ) > intervale_publication_SD ) //Publication toutes les x secondes sur la carte SD
{
File dataFile = SD.open("Temp_log.txt", FILE_WRITE);
if (dataFile)
{
dataFile.println(temperature_loop);
dataFile.close();
Serial.println("Ecriture SD");
}
else
{
Serial.println("error opening datalog.txt");
}
}
if(! mqtt_AIO.ping()) // ping the server to keep the mqtt connection alive
{
mqtt_AIO.disconnect();
}
if(! mqtt_Local.ping())
{
mqtt_Local.disconnect();
}
}
/************************* Voids *****************************/
void MQTT_AIO_connect()
{
int8_t ret;
// Stop if already connected.
if (mqtt_AIO.connected())
{
return;
}
Serial.print("Connecting to MQTT AIO... ");
while ((ret = mqtt_AIO.connect()) != 0) { // connect will return 0 for connected
Serial.println(mqtt_AIO.connectErrorString(ret));
Serial.println("Retrying MQTT AIO connection in 5 seconds...");
mqtt_AIO.disconnect();
delay(5000); // wait 5 seconds
}
Serial.println("MQTT AIO Connected!");
}
void MQTT_Local_connect()
{
int8_t ret2;
// Stop if already connected.
if (mqtt_Local.connected())
{
return;
}
Serial.print("Connecting to MQTT Local... ");
while ((ret2 = mqtt_Local.connect()) != 0) { // connect will return 0 for connected
Serial.println(mqtt_Local.connectErrorString(ret2));
Serial.println("Retrying MQTT Local connection in 5 seconds...");
mqtt_Local.disconnect();
delay(5000); // wait 5 seconds
}
Serial.println("MQTT Local Connected!");
}
Keisar
5
This morning again the temperatures went cray, I unplug the sensor itself from the cable and put i back 30 secs and all good.
Is there a way the sensor itself overheat ?
b707
6
I don't see anything incorrect in your code...
amitf
7
Does resetting also make it working fine?
Keisar
8
When I reset or unscrew that bit and unplug / plug the sensor it work fine for a while.
amitf
9
may be a simple way to solve it is to use resetFunc(); function ever hour
b707
10
perhaps just clean the contacts?
PaulRB
11
It appears to me like you might have a faulty sensor. I've used sht20 in similar packages but I've never seen them do that.
Keisar
12
Actually, I have switched from 5v to 3.3v and it runs like a charm since 2 days without any trouble.
Even if the specification mentioned 5v was fine...
