Sensor - DHT11 - Temperatuur, Luchtvochtigheid sensor

Hardware

Informatie

Met deze module kun je de temperatuur en luchtvochtigheid meten, hij is door de fabrikant al behoorlijk geijkt, eventuele aanpassingen (bijvoorbeeld ijken) kunnen softwarematig gedaan worden, de meetwaarden van de DHT22 zijn nauwkeuriger dan zijn broertje, de DHT11.

– Werkt op: 3-5V.
– 2.5mA max stroomverbruik wanneer data opgevraagd wordt.
– Temperatuur bereik: -40 t/m 80 ºC.
– Temperatuur nauwkeurigheid: ±0,5 ºC.
– Vochtigheid bereik: 20-95% RH.
– Vochtigheid nauwkeurigheid: ±5,0% RH.
– Response tijd: < 5 sec.

Let op: de DHT11 geeft geen decimalen weer, de DHT22 wel!

Ps. Voor velen wordt deze sensor als een oude reliek gezien, maar….het is de enige sensor die kan communiceren over lange afstanden met kabel, de modernere sensoren hebben een I2C of SPI interface, en zijn daardoor beperkt met een max. kabellengte van 15-30 cm!

Vergelijking tussen de DHT121 en DHT22:

Pinout

Pin:	Functie:
01	+5V
02	Data
03	NC (niet aangesloten)
04	GND

Arduino

De sensor werkt met binaire data, er zijn daarvoor diverse bibliotheeken geschreven om het makkelijk te maken.

1) Weerstand 4,7 kOhm
2) Arduino DHT bibliotheek

Sluit de module aan volgens onderstaand overzicht:

Ps. de weerstand is nodig voor de pull-up!

Arduino pin:	BMP280 pin:
+5V	+5V (VCC)
GND	GND
A5	SCL Serial Clock (line)
A4	SCA Serial Clock (data)

Script (voorbeeld Markruys bibliotheek)

#include "DHT.h"
DHT dht;
 
void setup() {
	Serial.begin(9600);
	Serial.println();
	Serial.println("Status\tVochtigheid (%)\tTemperatuur (C)\t(F)");
	// DHT aangesloten op data pin 2.
	dht.setup(2);
}
 
void loop() {
	delay(dht.getMinimumSamplingPeriod());
 
	// Haal de data uit de DHT module en zet deze om in een variabele.
	float vochtigheid = dht.getHumidity();
	float temperatuur = dht.getTemperature();
 
	// Print de gegevens naar de seriele monitor.
	Serial.print(dht.getStatusString());
	Serial.print("\t");
	Serial.print(vochtigheid, 1);
	Serial.print("\t\t");
	Serial.print(temperatuur, 1);
	Serial.print("\t\t");
	Serial.println(dht.toFahrenheit(temperatuur), 1);
}

#include "DHT.h"

DHT dht;

void setup() {

Serial.begin(9600);

Serial.println();

Serial.println("Status\tVochtigheid (%)\tTemperatuur (C)\t(F)");

// DHT aangesloten op data pin 2.

dht.setup(2);

}

void loop() {

delay(dht.getMinimumSamplingPeriod());

// Haal de data uit de DHT module en zet deze om in een variabele.

float vochtigheid = dht.getHumidity();

float temperatuur = dht.getTemperature();

// Print de gegevens naar de seriele monitor.

Serial.print(dht.getStatusString());

Serial.print("\t");

Serial.print(vochtigheid, 1);

Serial.print("\t\t");

Serial.print(temperatuur, 1);

Serial.print("\t\t");

Serial.println(dht.toFahrenheit(temperatuur), 1);

}

Output

Script (RobTillaart “DHTlib” library)

Voorbeeld met een DHT22 sensor

#include "DHT.h"
DHT dht;
 
void setup() {
	Serial.begin(9600);
	Serial.println();
	Serial.println("StatustVochtigheid (%)tTemperatuur (C)t(F)");
	// DHT aangesloten op data pin 2.
	dht.setup(2);
}
 
void loop() {
	delay(dht.getMinimumSamplingPeriod());
 
	// Haal de data uit de DHT module en zet deze om in een variabele.
	float vochtigheid = dht.getHumidity();
	float temperatuur = dht.getTemperature();
 
	// Print de gegevens naar de seriele monitor.
	Serial.print(dht.getStatusString());
	Serial.print("t");
	Serial.print(vochtigheid, 1);
	Serial.print("tt");
	Serial.print(temperatuur, 1);
	Serial.print("tt");
	Serial.println(dht.toFahrenheit(temperatuur), 1);
}

#include "DHT.h"

DHT dht;

void setup() {

Serial.begin(9600);

Serial.println();

Serial.println("StatustVochtigheid (%)tTemperatuur (C)t(F)");

// DHT aangesloten op data pin 2.

dht.setup(2);

}

void loop() {

delay(dht.getMinimumSamplingPeriod());

// Haal de data uit de DHT module en zet deze om in een variabele.

float vochtigheid = dht.getHumidity();

float temperatuur = dht.getTemperature();

// Print de gegevens naar de seriele monitor.

Serial.print(dht.getStatusString());

Serial.print("t");

Serial.print(vochtigheid, 1);

Serial.print("tt");

Serial.print(temperatuur, 1);

Serial.print("tt");

Serial.println(dht.toFahrenheit(temperatuur), 1);

}

Output

Arduino Library

Installatie van Arduino IDE libraries: Arduino info

DHT informatie @ Arduino Playground

RobTillaart “DHTlib” library (aanbevolen voor Arduino)

The DHT11, 21, 22, 33 and 44 are relative inexpensive sensors for measuring temperature and humidity.

This library can be used for reading both values from these DHT sensors.
The DHT11 only returns integers (e.g. 20) and does not support negative values.
The others are quite similar and provide one decimal digit (e.g. 20.2)
The hardware pins of the sensors and handshake are identical so ideal to combine in one lib.

The library (0.1.13 version) is confirmed to work on:

UNO (tested myself)
2009 (tested myself)
MEGA2560
DUE
attiny85 @8MHz
Digistump Digix @ 84 MHz

version 0.1.13 is the last stable version for both AVR and ARM
version 0.1.14 and up are not compatible anymore with pre 1.0 Arduino
version 0.1.14 and up have breaking changes wrt ARM based arduino's e.g DUE.
version 0.1.15 is stable version for AVR only
version 0.1.16 and 0.1.17 have breaking changes for DHT11
version 0.1.18 works again for DHT11 (avr only)
version 0.1.19 fixed masking bug DHT11 (avr only)
version 0.1.20 Reduce footprint (34 bytes) by using int8_t as error codes. (thanks to chaveiro)
version 0.1.21 replace delay with delayMicroseconds() + small fix (thanks to codingforfun)

version 0.1.13 is the last stable version for both AVR and ARM

version 0.1.14 and up are not compatible anymore with pre 1.0 Arduino

version 0.1.14 and up have breaking changes wrt ARM based arduino's e.g DUE.

version 0.1.15 is stable version for AVR only

version 0.1.16 and 0.1.17 have breaking changes for DHT11

version 0.1.18 works again for DHT11 (avr only)

version 0.1.19 fixed masking bug DHT11 (avr only)

version 0.1.20 Reduce footprint (34 bytes) by using int8_t as error codes. (thanks to chaveiro)

version 0.1.21 replace delay with delayMicroseconds() + small fix (thanks to codingforfun)

Dowload Robtillaart DHTlib library @ Github

Markruys “arduino-DHT” library (arduino)

Ondersteuning voor DHT11. DHT22, AM2302, RHT03.
Detecteert automatisch het sensor model.
Verbruikt weinig geheugen.
Zeer kleine code.

Dowload Markruys arduino-DHT library @ Github

Adafruit “DHT library” (arduino)

This is an Arduino library for the DHT series of low cost temperature/humidity sensors.

To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder DHT. Check that the DHT folder contains DHT.cpp and DHT.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.

Dowload Adafruit DHT library @ Github

Niesteszeck “idDHT11” library

De DHT bibliotheek van Niesteszeck is interrupt gedreven en belast de atmega minder, zodat er capaciteit overblijft voor andere taken.

Dowload Niesteszeck – idDHT11 library @ Github

Bronnen:
ControlEverythongCommunity @ Github.com
raspberrypi-spy.co.uk

Robtillaart - DHTlib v0.1.21.7z 4,54 kb
Robtillaart - DHTlib v0.1.19.7z 4,24 kb
Robtillaart - DHTlib v0.1.15.7z 3,82 kb
Robtillaart - DHTlib v0.1.14.7z 3,44 kb
Robtillaart - DHTlib v0.1.13.7z 3,22 kb
Robtillaart - DHTlib v0.1.09.7z 2,79 kb
Niesteszeck - idDHT11 v0.1 (interrupt gedreven).7z 3,75 kb
Markruys - arduino-DHT v2013-07-01.7z 41,07 kb
Adafruit - DHT-sensor-library v1.2.3.7z 4,97 kb
Adafruit - DHT-sensor-library v1.0.0 (gedownload op 2015-02-07).7z 3,06 kb

Raspberry Pi

Let op: Soms krijg je geen uitslag/resultaat van de scripts, dat komt omdat Linux de (precieze) timing van de aanroepen niet kan garanderen!, bij voorkeur zijn de DHT sensoren niet geschikt voor een Raspberry Pi

De sensor werkt met binaire data, er is daarvoor een bibliotheek geschreven om het makkelijk te maken.

1) Python DHT sensors bibliotheek

Aansluiten op de Raspberry Pi

Sluit de DHT sensor aan zoals aangegeven op onderstaand schema:

Raspberry Pi pin:	DHT11 pin:
1 (+3.3v)	1 (+3.3 - 5v)
7	2 (data)
14 (GND)	4 (GND)

Ps. de weerstand is nodig voor de pull-up!

Raspberry Pi pin:	DHT22 pin:
1 (+3.3v)	1 (+3.3 - 5v)
18	2 (data)
14 (GND)	4 (GND)

Scripts

Onderstaand script leest eenvoudig een DHT 11 sensor uit op GPIO 4, en geeft de waarden weer via de console.

Maak een bestand aan, bijvoorbeeld /usr/src/dht.py (evt onder root, en vergeet niet chmod te gebruiken om het bestand uit te kunnen voeren), voeg deze inhoud daar in toe:

# Importeer Adafruit DHT bibliotheek.
import Adafruit_DHT

humidity, temperature = Adafruit_DHT.read_retry(Adafruit_DHT.DHT11, 4)

humidity = round(humidity, 2)
temperature = round(temperature, 2)

if humidity is not None and temperature is not None:
  print 'Temperatuur = {0:0.1f}*C  Luchtvochtigheid = {1:0.1f}%'.format(temperature, humidity)
else:
  print 'Kan de sensor niet uitlezen!'

# Importeer Adafruit DHT bibliotheek.

import Adafruit_DHT

humidity, temperature = Adafruit_DHT.read_retry(Adafruit_DHT.DHT11, 4)

humidity = round(humidity, 2)

temperature = round(temperature, 2)

if humidity is not None and temperature is not None:

print 'Temperatuur = {0:0.1f}*C Luchtvochtigheid = {1:0.1f}%'.format(temperature, humidity)

else:

print 'Kan de sensor niet uitlezen!'

Commandolijn parameters

Wil je commandolijn parameters gebruiken?, bijvoorbeeld als je meerdere DHT sensors hebt aangesloten via de GPIO pinnen, gebruik deze voorbeeld code.

Start het script met commandolijn: sudo python /usr/src/dht.py [11/22/2302] [GPIO pin]

Het commando sudo python /usr/src/dht.py 22 24 leest bijvoorbeeld een DHT22 sensor uit die aangesloten is op GPIO pin 24 (Broadcom SOC)

# Importeer Adafruit DHT bibliotheek.
import Adafruit_DHT
# Importeer bibliotheek voor systeemfuncties.
import sys

# Commandolijn parameters verwerken.
sensor_args = { '11': Adafruit_DHT.DHT11,
                '22': Adafruit_DHT.DHT22,
                '2302': Adafruit_DHT.AM2302 }
if len(sys.argv) == 3 and sys.argv[1] in sensor_args:
  sensor = sensor_args[sys.argv[1]]
  pin = sys.argv[2]

humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

humidity = round(humidity, 2)
temperature = round(temperature, 2)

if humidity is not None and temperature is not None:
  print 'Temperatuur = {0:0.1f}*C  Luchtvochtigheid = {1:0.1f}%'.format(temperature, humidity)
else:
  print 'Kan de sensor niet uitlezen!'

# Importeer Adafruit DHT bibliotheek.

import Adafruit_DHT

# Importeer bibliotheek voor systeemfuncties.

import sys

# Commandolijn parameters verwerken.

sensor_args = { '11': Adafruit_DHT.DHT11,

'22': Adafruit_DHT.DHT22,

'2302': Adafruit_DHT.AM2302 }

if len(sys.argv) == 3 and sys.argv[1] in sensor_args:

sensor = sensor_args[sys.argv[1]]

pin = sys.argv[2]

humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

humidity = round(humidity, 2)

temperature = round(temperature, 2)

if humidity is not None and temperature is not None:

print 'Temperatuur = {0:0.1f}*C Luchtvochtigheid = {1:0.1f}%'.format(temperature, humidity)

else:

print 'Kan de sensor niet uitlezen!'

Gegevens wegschrijven naar CSV bestand

Je kan de gegevens ook opslaan in een CSV bestand, onderstaand script maakt ook gebruik van de commandolijn parameters en slaat gegevens op in een bestand (per maand) in /usr/src/DHT_DATA_[YYYY]_[MM].csv

# Importeer Adafruit DHT bibliotheek.
import Adafruit_DHT
# Importeer bibliotheek voor systeemfuncties.
import sys
# Importeer bibliotheek voor tijdfuncties.
import time
# Importeer bibliotheek voor CSV functies.
import csv

# Definieer variabelen.
DY = time.strftime("%Y")
DM = time.strftime("%m")
DD = time.strftime("%d")
TH = time.strftime("%H")
TM = time.strftime("%M")

# Commandolijn parameters verwerken.
sensor_args = { '11': Adafruit_DHT.DHT11,
                '22': Adafruit_DHT.DHT22,
                '2302': Adafruit_DHT.AM2302 }
if len(sys.argv) == 3 and sys.argv[1] in sensor_args:
  sensor = sensor_args[sys.argv[1]]
  pin = sys.argv[2]

humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

humidity = round(humidity, 2)
temperature = round(temperature, 2)

if humidity is not None and temperature is not None:
  print 'Temperatuur = {0:0.1f}*C  Luchtvochtigheid={1:0.1f}%'.format(temperature, humidity)
else:
  print 'Kan de sensor niet uitlezen!'

data = [DY, DM, DD, TH, TM, humidity, temperature]
# Sla gegevens op in een bestand (per maand) in /usr/src/DHT_DATA_[YYYY]_[MM].csv
csvfile = "/usr/src/DHT_DATA_" + DY + DM + ".csv"

# Open het csv bestand en schijf door achter de bestaande inhoud.
with open(csvfile, "a") as output:
  writer = csv.writer(output, delimiter=";", lineterminator='\n')
  writer.writerow(data)

# Importeer Adafruit DHT bibliotheek.

import Adafruit_DHT

# Importeer bibliotheek voor systeemfuncties.

import sys

# Importeer bibliotheek voor tijdfuncties.

import time

# Importeer bibliotheek voor CSV functies.

import csv

# Definieer variabelen.

DY = time.strftime("%Y")

DM = time.strftime("%m")

DD = time.strftime("%d")

TH = time.strftime("%H")

TM = time.strftime("%M")

# Commandolijn parameters verwerken.

sensor_args = { '11': Adafruit_DHT.DHT11,

'22': Adafruit_DHT.DHT22,

'2302': Adafruit_DHT.AM2302 }

if len(sys.argv) == 3 and sys.argv[1] in sensor_args:

sensor = sensor_args[sys.argv[1]]

pin = sys.argv[2]

humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

humidity = round(humidity, 2)

temperature = round(temperature, 2)

if humidity is not None and temperature is not None:

print 'Temperatuur = {0:0.1f}*C Luchtvochtigheid={1:0.1f}%'.format(temperature, humidity)

else:

print 'Kan de sensor niet uitlezen!'

data = [DY, DM, DD, TH, TM, humidity, temperature]

# Sla gegevens op in een bestand (per maand) in /usr/src/DHT_DATA_[YYYY]_[MM].csv

csvfile = "/usr/src/DHT_DATA_" + DY + DM + ".csv"

# Open het csv bestand en schijf door achter de bestaande inhoud.

with open(csvfile, "a") as output:

writer = csv.writer(output, delimiter=";", lineterminator='\n')

writer.writerow(data)

De inhoud van het CSV bestand ziet er zo uit:

2015;03;13;13;56;35.0;23.0
2015;03;13;13;59;35.0;23.0
2015;03;13;14;06;35.0;23.0
2015;03;13;14;06;35.0;23.0
2015;03;13;14;06;36.0;23.0
2015;03;13;14;06;47.0;29.0

2015;03;13;13;56;35.0;23.0

2015;03;13;13;59;35.0;23.0

2015;03;13;14;06;35.0;23.0

2015;03;13;14;06;36.0;23.0

2015;03;13;14;06;47.0;29.0

Script met Adafruit bibliotheek

Onderstaand script leest eenvoudig een DHT 22 sensor uit op GPIO 18, en geeft de waarden weer via de console.

Maak een bestand aan, bijvoorbeeld /usr/src/dht.py (evt onder root, en vergeet niet chmod te gebruiken om het bestand uit te kunnen voeren), voeg deze inhoud daar in toe:

#!/usr/bin/python
import Adafruit_DHT

gpiopin = 18
HUM = 0.0
TEMP = 0.0
HUM, TEMP = Adafruit_DHT.read(Adafruit_DHT.DHT22, gpiopin)
if HUM >0 and TEMP >0:
  HUM = round(HUM, 2)
  TEMP = round(TEMP, 2)
  print '{0:0.1f}'.format(TEMP) + ';' + '{0:0.1f}'.format(HUM)
else:
  print '0;0'

#!/usr/bin/python

import Adafruit_DHT

gpiopin = 18

HUM = 0.0

TEMP = 0.0

HUM, TEMP = Adafruit_DHT.read(Adafruit_DHT.DHT22, gpiopin)

if HUM >0 and TEMP >0:

HUM = round(HUM, 2)

TEMP = round(TEMP, 2)

print '{0:0.1f}'.format(TEMP) + ';' + '{0:0.1f}'.format(HUM)

else:

print '0;0'

Bronnen:
community.mydevices.com
raspberrytips.nl

Python Library

Python library to read the DHT series of humidity and temperature sensors on a Raspberry Pi or Beaglebone Black.

Currently the library is only tested with Python 2.6/2.7.

For all platforms (Raspberry Pi and Beaglebone Black) make sure your system is able to compile Python extensions. On Raspbian or Beaglebone Black’s Debian/Ubuntu image you can ensure your system is ready by executing:

apt-get update
sudo apt-get install build-essential python-dev

1 2	apt-get update sudo apt-get install build-essential python-dev

Installatie via GIT (github)

cd /usr/src/
sudo git clone https://github.com/adafruit/Adafruit_Python_DHT.git

1 2	cd /usr/src/ sudo git clone https://github.com/adafruit/Adafruit_Python_DHT.git

Cloning into 'Adafruit_Python_DHT'...
remote: Counting objects: 112, done.
remote: Total 112 (delta 0), reused 0 (delta 0), pack-reused 112
Receiving objects: 100% (112/112), 38.30 KiB, done.
Resolving deltas: 100% (66/66), done.

Cloning into 'Adafruit_Python_DHT'...

remote: Counting objects: 112, done.

remote: Total 112 (delta 0), reused 0 (delta 0), pack-reused 112

Receiving objects: 100% (112/112), 38.30 KiB, done.

Resolving deltas: 100% (66/66), done.

cd Adafruit_Python_DHT
sudo python setup.py install

1 2	cd Adafruit_Python_DHT sudo python setup.py install

Downloading https://pypi.python.org/packages/source/s/setuptools/setuptools-4.0.1.zip
Extracting in /tmp/tmpbzKAm3
Now working in /tmp/tmpbzKAm3/setuptools-4.0.1
Building a Setuptools egg in /usr/src/Adafruit_Python_DHT
/usr/src/Adafruit_Python_DHT/setuptools-4.0.1-py2.7.egg
running install
running bdist_egg
running egg_info
creating Adafruit_DHT.egg-info
writing Adafruit_DHT.egg-info/PKG-INFO
writing top-level names to Adafruit_DHT.egg-info/top_level.txt
writing dependency_links to Adafruit_DHT.egg-info/dependency_links.txt
writing manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'
reading manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'
writing manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'
installing library code to build/bdist.linux-armv6l/egg
running install_lib
running build_py
creating build
creating build/lib.linux-armv6l-2.7
creating build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/common.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/Beaglebone_Black.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/__init__.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/Raspberry_Pi_2.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/Raspberry_Pi.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/Test.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
copying Adafruit_DHT/platform_detect.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT
running build_ext
building 'Adafruit_DHT.Raspberry_Pi_Driver' extension
creating build/temp.linux-armv6l-2.7
creating build/temp.linux-armv6l-2.7/source
creating build/temp.linux-armv6l-2.7/source/Raspberry_Pi
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/inclu               de/python2.7 -c source/_Raspberry_Pi_Driver.c -o build/temp.linux-armv6l-2.7/source/_Raspberry_Pi_Driv               er.o -std=gnu99
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/common_dht_read.c -o build/temp.linux-armv6l-2.7/source/common_dht_read.o -std=gnu99
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/Raspberry_Pi/pi_dht_read.c -o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_dht_read.o -std=gnu99
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/Raspberry_Pi/pi_mmio.c -o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_mmio.o -std=gnu99
gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-z,relro build/temp.linux-armv6l-2.7/source/_Raspberry_Pi_Driver.o build/temp.linux-armv6l-2.7/source/common_dht_read.o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_dht_read.o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_mmio.o -lrt -o build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_Driver.so
creating build/bdist.linux-armv6l
creating build/bdist.linux-armv6l/egg
creating build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_Driver.so -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/common.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Beaglebone_Black.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/__init__.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_2.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Test.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
copying build/lib.linux-armv6l-2.7/Adafruit_DHT/platform_detect.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/common.py to common.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Beaglebone_Black.py to Beaglebone_Black.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/__init__.py to __init__.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi_2.py to Raspberry_Pi_2.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi.py to Raspberry_Pi.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Test.py to Test.pyc
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/platform_detect.py to platform_detect.pyc
creating stub loader for Adafruit_DHT/Raspberry_Pi_Driver.so
byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi_Driver.py to Raspberry_Pi_Driver.pyc
creating build/bdist.linux-armv6l/egg/EGG-INFO
copying Adafruit_DHT.egg-info/PKG-INFO -> build/bdist.linux-armv6l/egg/EGG-INFO
copying Adafruit_DHT.egg-info/SOURCES.txt -> build/bdist.linux-armv6l/egg/EGG-INFO
copying Adafruit_DHT.egg-info/dependency_links.txt -> build/bdist.linux-armv6l/egg/EGG-INFO
copying Adafruit_DHT.egg-info/top_level.txt -> build/bdist.linux-armv6l/egg/EGG-INFO
writing build/bdist.linux-armv6l/egg/EGG-INFO/native_libs.txt
zip_safe flag not set; analyzing archive contents...
creating dist
creating 'dist/Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg' and adding 'build/bdist.linux-armv6l/egg' to it
removing 'build/bdist.linux-armv6l/egg' (and everything under it)
Processing setuptools-4.0.1-py2.7.egg
Copying setuptools-4.0.1-py2.7.egg to /usr/local/lib/python2.7/dist-packages
Adding setuptools 4.0.1 to easy-install.pth file
Installing easy_install script to /usr/local/bin
Installing easy_install-2.7 script to /usr/local/bin

Installed /usr/local/lib/python2.7/dist-packages/setuptools-4.0.1-py2.7.egg
Processing dependencies for setuptools==4.0.1
Finished processing dependencies for setuptools==4.0.1
Processing Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg
Copying Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg to /usr/local/lib/python2.7/dist-packages
Adding Adafruit-DHT 1.1.0 to easy-install.pth file

Installed /usr/local/lib/python2.7/dist-packages/Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg
Processing dependencies for Adafruit-DHT==1.1.0
Finished processing dependencies for Adafruit-DHT==1.1.0

Downloading https://pypi.python.org/packages/source/s/setuptools/setuptools-4.0.1.zip

Extracting in /tmp/tmpbzKAm3

Now working in /tmp/tmpbzKAm3/setuptools-4.0.1

Building a Setuptools egg in /usr/src/Adafruit_Python_DHT

/usr/src/Adafruit_Python_DHT/setuptools-4.0.1-py2.7.egg

running install

running bdist_egg

running egg_info

creating Adafruit_DHT.egg-info

writing Adafruit_DHT.egg-info/PKG-INFO

writing top-level names to Adafruit_DHT.egg-info/top_level.txt

writing dependency_links to Adafruit_DHT.egg-info/dependency_links.txt

writing manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'

reading manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'

writing manifest file 'Adafruit_DHT.egg-info/SOURCES.txt'

installing library code to build/bdist.linux-armv6l/egg

running install_lib

running build_py

creating build

creating build/lib.linux-armv6l-2.7

creating build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/common.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/Beaglebone_Black.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/__init__.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/Raspberry_Pi_2.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/Raspberry_Pi.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/Test.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

copying Adafruit_DHT/platform_detect.py -> build/lib.linux-armv6l-2.7/Adafruit_DHT

running build_ext

building 'Adafruit_DHT.Raspberry_Pi_Driver' extension

creating build/temp.linux-armv6l-2.7

creating build/temp.linux-armv6l-2.7/source

creating build/temp.linux-armv6l-2.7/source/Raspberry_Pi

gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/inclu de/python2.7 -c source/_Raspberry_Pi_Driver.c -o build/temp.linux-armv6l-2.7/source/_Raspberry_Pi_Driv er.o -std=gnu99

gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/common_dht_read.c -o build/temp.linux-armv6l-2.7/source/common_dht_read.o -std=gnu99

gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/Raspberry_Pi/pi_dht_read.c -o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_dht_read.o -std=gnu99

gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c source/Raspberry_Pi/pi_mmio.c -o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_mmio.o -std=gnu99

gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-z,relro build/temp.linux-armv6l-2.7/source/_Raspberry_Pi_Driver.o build/temp.linux-armv6l-2.7/source/common_dht_read.o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_dht_read.o build/temp.linux-armv6l-2.7/source/Raspberry_Pi/pi_mmio.o -lrt -o build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_Driver.so

creating build/bdist.linux-armv6l

creating build/bdist.linux-armv6l/egg

creating build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_Driver.so -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/common.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Beaglebone_Black.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/__init__.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi_2.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Raspberry_Pi.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/Test.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

copying build/lib.linux-armv6l-2.7/Adafruit_DHT/platform_detect.py -> build/bdist.linux-armv6l/egg/Adafruit_DHT

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/common.py to common.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Beaglebone_Black.py to Beaglebone_Black.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/__init__.py to __init__.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi_2.py to Raspberry_Pi_2.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi.py to Raspberry_Pi.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Test.py to Test.pyc

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/platform_detect.py to platform_detect.pyc

creating stub loader for Adafruit_DHT/Raspberry_Pi_Driver.so

byte-compiling build/bdist.linux-armv6l/egg/Adafruit_DHT/Raspberry_Pi_Driver.py to Raspberry_Pi_Driver.pyc

creating build/bdist.linux-armv6l/egg/EGG-INFO

copying Adafruit_DHT.egg-info/PKG-INFO -> build/bdist.linux-armv6l/egg/EGG-INFO

copying Adafruit_DHT.egg-info/SOURCES.txt -> build/bdist.linux-armv6l/egg/EGG-INFO

copying Adafruit_DHT.egg-info/dependency_links.txt -> build/bdist.linux-armv6l/egg/EGG-INFO

copying Adafruit_DHT.egg-info/top_level.txt -> build/bdist.linux-armv6l/egg/EGG-INFO

writing build/bdist.linux-armv6l/egg/EGG-INFO/native_libs.txt

zip_safe flag not set; analyzing archive contents...

creating dist

creating 'dist/Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg' and adding 'build/bdist.linux-armv6l/egg' to it

removing 'build/bdist.linux-armv6l/egg' (and everything under it)

Processing setuptools-4.0.1-py2.7.egg

Copying setuptools-4.0.1-py2.7.egg to /usr/local/lib/python2.7/dist-packages

Adding setuptools 4.0.1 to easy-install.pth file

Installing easy_install script to /usr/local/bin

Installing easy_install-2.7 script to /usr/local/bin

Installed /usr/local/lib/python2.7/dist-packages/setuptools-4.0.1-py2.7.egg

Processing dependencies for setuptools==4.0.1

Finished processing dependencies for setuptools==4.0.1

Processing Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg

Copying Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg to /usr/local/lib/python2.7/dist-packages

Adding Adafruit-DHT 1.1.0 to easy-install.pth file

Installed /usr/local/lib/python2.7/dist-packages/Adafruit_DHT-1.1.0-py2.7-linux-armv6l.egg

Processing dependencies for Adafruit-DHT==1.1.0

Finished processing dependencies for Adafruit-DHT==1.1.0

Download Adafruit_Python_DHT @ Github

Afmetingen

Teardown

Inside the case is a small PCB with a SOIC 14 packaged IC unfortunately the part number has been removed so there is really no way to tell if this is a custom part or a specially programmed MCU. along the edge of the IC are couple of ceramic capacitors for decoupling and noise suppression, and some other misc passive components. The green resistor I can assume is a precision resistor for the humility sensor (explained in more detail later).

On the other side the sensor hardware itself. This consists of a PCB with interlaced traces that creates capacitance this with change based on the amount of moisture present in the air around it.

HOW DOES IT WORK

The interlaced +ive and -ive traces allow a small amount of charge to be stored in each of the traces allowing the circuit to charge up a little, this is called capacitance and this is effected by the material separating the +ive and -ive which is mostly air and its airs permittivity one of the factors for calculating capacitance is affected by temperature and humidity.

So the chip uses the precision resistor I mentioned earlier and measures the discharge time through that resistor to calculate the capacitance, and then uses that figure used with the internal temperature sensor inside the main IC to calculate the relative humidity.