💬 Air Humidity Sensor - DHT

[hek]

@skywatch said:

Now I can sleep at night again

Haha, yeah, good to hear you will get a good nights sleep again.

[flopp]

@skywatch said:

Hurrah! :)

Now I can sleep at night again ;)

Good job!

haha, me too :)

[Pavel Larkin]

Hello. Maybe someone could help :) hopefully..
I have arduino1 with 1 DHT22, which is over arduinoGW connected to RSPi with latest domoticz.
when i connect stuff up, after some time i see some strange childids, not related to this arduino1 in no way.
Lots of unknown!, with V_TEMP values, with V_HUM values, even V_FORECAST, V_PRESSURE and etc. which arduino1 should not send (or no other arduino on my area).

Illustration:
<img href="http://www.lstudio.lt/wp-content/uploads/dht22problem.png">
http://www.lstudio.lt/wp-content/uploads/dht22problem.png

my code is quite simple (for ex only temperature is shown)

#define CHILD_DESCR "TEMP3"
#undef CHILD_ID
#define CHILD_ID 31
present(CHILD_ID, S_TEMP, CHILD_DESCR);
delay(250) ;

loop:

  temp3=dht3.readTemperature();

if (temp3 >= 120) {temp3 = lasttemp3;}
if (temp3 <= -50) {temp3 = lasttemp3;}
MyMessage msg31(CHILD_ID,V_TEMP);
send(msg31.set(temp3,1));

so.. that is basically all

[flopp]

@Pavel-Larkin

I have also seen this, I noticed it last week. Some of my Nodes have those Unknown-child, but it is working correctly anyway.
DZ 3.5877, MyS 1.5.1, RPi 2

[Gimlur]

Hello,
i have a problem with this sketch.
After downloading DTH.h froom Mysensors Examples, i have this error :
DhtTemperatureAndHumiditySensor:85: error: 'getConfig' was not declared in this scope

metric = getConfig().isMetric;

Any Idea of my mistake ?...

[hek]

It isn't your mistake, it's ours. The examples hasn't been updated correctly to reflect the most recent change in the api.

It should say getControllerConfig().isMetric

[johnecy]

I have the dht22 sensor hooked up and working on a pro mini on pin 3 I get a normal temp reading but the humidity always stays at 1.0 does not read.

[mfalkvidd]

@johnecy https://forum.mysensors.org/topic/5978/temperature-and-humidity-dht22

[donhuan78p]

Hello everybody,
hope, someone could help a newby :-)
I've installed the MQTT - GW and would use the Air/Humidity - sensor. But it doesn't work properly.
The Connection to the Gateway seems to be okay. But I get no Air/Humidity - Information.
The sensor does not measure anything.
I've tried to change the data - pin, I've tried the DHT11 and DHT22 - sensor. No choice.
I'm getting mad :-)

Thanks a lot.

[gohan]

Have you tried the basic arduino sketch that prints data to serial port?

[donhuan78p]

Hello,
thanks a lot for your answer.
Yes, I did. It produced the Messages as excepted.

[gohan]

So you'd better post your code so we can take a look at what is wrong with it.

[donhuan78p]

...sorry, Typo.
As expected :-)

[donhuan78p]

...no Problem:

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0: Henrik EKblad
 * Version 1.1 - 2016-07-20: Converted to MySensors v2.0 and added various improvements - Torben Woltjen (mozzbozz)
 * 
 * DESCRIPTION
 * This sketch provides an example of how to implement a humidity/temperature
 * sensor using a DHT11/DHT-22.
 *  
 * For more information, please visit:
 * http://www.mysensors.org/build/humidity
 * 
 */

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached 
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69
//#define MY_RS485
 
#include <SPI.h>
#include <MySensors.h>  
#include <DHT.h>

// Set this to the pin you connected the DHT's data pin to
#define DHT_DATA_PIN 2

// Set this offset if the sensor has a permanent small offset to the real temperatures
#define SENSOR_TEMP_OFFSET 0

// Sleep time between sensor updates (in milliseconds)
// Must be >1000ms for DHT22 and >2000ms for DHT11
static const uint64_t UPDATE_INTERVAL = 30000;

// Force sending an update of the temperature after n sensor reads, so a controller showing the
// timestamp of the last update doesn't show something like 3 hours in the unlikely case, that
// the value didn't change since;
// i.e. the sensor would force sending an update every UPDATE_INTERVAL*FORCE_UPDATE_N_READS [ms]
static const uint8_t FORCE_UPDATE_N_READS = 10;

#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1

float lastTemp;
float lastHum;
uint8_t nNoUpdatesTemp;
uint8_t nNoUpdatesHum;
bool metric = true;

MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
DHT dht;


void presentation()  
{ 
  // Send the sketch version information to the gateway
  Serial.println("Presentation");
  sendSketchInfo("TemperatureAndHumidity", "1.1");
  
  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID_HUM, S_HUM);
  present(CHILD_ID_TEMP, S_TEMP);
  
  metric = getConfig().isMetric;
}


void setup()
{
  Serial.println("vor Presentation");
  
  dht.setup(DHT_DATA_PIN); // set data pin of DHT sensor
  if (UPDATE_INTERVAL <= dht.getMinimumSamplingPeriod()) {
    Serial.println("Warning: UPDATE_INTERVAL is smaller than supported by the sensor!");
  }
  // Sleep for the time of the minimum sampling period to give the sensor time to power up
  // (otherwise, timeout errors might occure for the first reading)
  sleep(dht.getMinimumSamplingPeriod());
}


void loop()      
{  

  Serial.println("loop Anfang");
  
  // Force reading sensor, so it works also after sleep()
  dht.readSensor(true);
  
  // Get temperature from DHT library
  float temperature = dht.getTemperature();
  if (isnan(temperature)) {
    Serial.println("Failed reading temperature from DHT!");
  } else if (temperature != lastTemp || nNoUpdatesTemp == FORCE_UPDATE_N_READS) {
    // Only send temperature if it changed since the last measurement or if we didn't send an update for n times
    lastTemp = temperature;
    if (!metric) {
      temperature = dht.toFahrenheit(temperature);
    }
    // Reset no updates counter
    nNoUpdatesTemp = 0;
    temperature += SENSOR_TEMP_OFFSET;
    send(msgTemp.set(temperature, 1));

    #ifdef MY_DEBUG
    Serial.print("T: ");
    Serial.println(temperature);
    #endif
  } else {
    // Increase no update counter if the temperature stayed the same
    nNoUpdatesTemp++;
  }

  // Get humidity from DHT library
  float humidity = dht.getHumidity();
  if (isnan(humidity)) {
    Serial.println("Failed reading humidity from DHT");
  } else if (humidity != lastHum || nNoUpdatesHum == FORCE_UPDATE_N_READS) {
    // Only send humidity if it changed since the last measurement or if we didn't send an update for n times
    lastHum = humidity;
    // Reset no updates counter
    nNoUpdatesHum = 0;
    send(msgHum.set(humidity, 1));
    
   #ifdef MY_DEBUG
    Serial.print("H: ");
    Serial.println(humidity);
   #endif
  } else {
    // Increase no update counter if the humidity stayed the same
    nNoUpdatesHum++;
  }

  // Sleep for a while to save energy
  sleep(UPDATE_INTERVAL); 
}

[Arnold Šlepetis]

I am using dht22 outside. Does any one know how to change to whole number not decimal. The temperature outside change a lot. Let say temp 20.2 changed to 20.4 and still sends to getaway . If I do "send(msgTemp.set(temperature, 0));" and still receive both times 20 and 20, and I want only if change to 21 or 19.

[mfalkvidd]

@Arnold-Šlepetis change

float lastTemp;

to

signed int lastTemp;

and

float temperature = dht.getTemperature();

to

signed int temperature = dht.getTemperature() + 0.5; // Add 0.5 to get correct rounding

and

temperature = dht.toFahrenheit(temperature);

to

temperature = dht.toFahrenheit(temperature) + 0.5;

and

send(msgTemp.set(temperature, 1));

to

send(msgTemp.set(temperature));

You might also have to handle the isnan test.

[Arnold Šlepetis]

@mfalkvidd Thanks. It works like a charm

[jwosnick]

I've made a bit of an unusual observation in relationship to this script. I am running a fairly stripped-down version of it, but with the "standard" (not MySensors-customized) DHT library and its associated functions.

Here is the code:

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached 
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69
//#define MY_RS485

#define MY_NODE_ID 47

#include <SPI.h>
#include <MySensors.h>  
#include <DHT.h>

// Set this to the pin you connected the DHT's data pin to
#define DHT_DATA_PIN 5

// Set this offset if the sensor has a permanent small offset to the real temperatures
#define SENSOR_TEMP_OFFSET 0

// Sleep time between sensor updates (in milliseconds)
// Must be >1000ms for DHT22 and >2000ms for DHT11
static const uint64_t UPDATE_INTERVAL = 10000;

#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1

bool metric = true;

MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
DHT dht(DHT_DATA_PIN, DHT22);
float temperature;
float humidity;

void presentation()  
{ 
  // Send the sketch version information to the gateway
  sendSketchInfo("TemperatureAndHumidity", "1.1");

  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID_HUM, S_HUM);
  present(CHILD_ID_TEMP, S_TEMP);

  metric = getControllerConfig().isMetric;
}


void setup()
{
  delay(100);
}


void loop()      
{  
  
  // Get temperature from DHT library
  temperature = dht.readTemperature();
  if (isnan(temperature))
  {
    Serial.println("Failed reading temperature from DHT!");
  }
    
  else
  {
    send(msgTemp.set(temperature,0));
    #ifdef MY_DEBUG
    Serial.print("T: ");
    Serial.println(temperature);
    #endif
  }  

  // Get humidity from DHT library
  
  humidity = dht.readHumidity();
  if (isnan(humidity))
  {
    Serial.println("Failed reading humidity from DHT!");
  }
    
  else 
  {
    send(msgHum.set(humidity,1));
    #ifdef MY_DEBUG
    Serial.print("H: ");
    Serial.println(humidity);
    #endif
  }

  // Sleep for a while to save energy
  sleep(UPDATE_INTERVAL); 
}

I find that if I leave the last line as
sleep(UPDATE_INTERVAL);
then the sensor node ends up sending the same temperature and humidity values, over and over again, even if the actual humidity and temperature change.

However, if I change the last line to
delay(UPDATE_INTERVAL);
then everything works as expected.

This is with known good DHT22 units, so I suspect there is something funny about the sleep() function and the operation of the standard (not customized) DHT library.

It took a lot of poking around to discover this, but is this in fact the reason why the MySensors customized DHT library is required for this script? Is that library necessary to make sleep() and DHT temperature measurements play nicely together?

[gohan]

What libraries versions are you using?

[mfalkvidd]

@jwosnick the example sketch has this:

  // Force reading sensor, so it works also after sleep()
dht.readSensor(true);

which is missing in your sketch. The comment suggests that it might be relevant.