![Image](https://hobbycomponents.com/images/forum/mLink/HCMODU0181_3.jpg)
![](https://hobbycomponents.com/images/forum/forum/Description.png)
The mLink DHT22 sensor is a serial (I2C/IIC) temperature and humidity sensor module. It adds the ability of your microcontoller/Arduino to measure temperature (in oC) and relative humidity (%RH) to 1 decimal place using only its I2C interface. It is compatible with other mLink or standard I2C modules allowing you to daisy-chain several different types of modules together using only the two I2C pins of your microcontroller.
For Arduino users you can use the mLink library (see below) to control any type of mLink module. Only one single instance of the library is needed to control multiple types of mLink modules resulting in very little resources overhead and therefore making it great for Arduinos with small amounts of memory and pin counts.
For Raspberry Pi users we have a Python module which can be installed via pip or downloaded and installed directly from our forum. Please see the mLink Python forum thread for requirements and download link here: viewtopic.php?f=131&t=3062&p=8592#p8592
Module specifications:
Module code: HCMODU0181 Supply Voltage (VDD): 3.3V to 5.5V Current consumption (idle): 5mA Current consumption (sleep): 1.5mA Interfaces: I2C I2C Interface speed: 400kbits/s (fast mode) I2C default address (HEX): 0h51 Maximum number of modules: 5 with pullups fitted, 112 with pullups removed* Module dimensions (inc headers): 64mm x 17mm x 11.5mm DHT22 specifications: Operating range: Humidity 0-100%RH Temperature -40~80 Celsius Accuracy: Humidity +-2%RH(Max +-5%RH) Temperature <+-0.5Celsius Resolution or sensitivity: Humidity 0.1%RH Temperature 0.1Celsius Repeatability: humidity +-1%RH Temperature +-0.2Celsius Humidity hysteresis: +-0.3%RH Long-term Stability +-0.5%RH/year Sensing period Average: 2s *Note the maximum number of connected modules will depend on cable lengths and power requirements of each module. Do not exceed 5 mLink modules connected in series with all fitted to all modules.
Arduino Connection Example:
![Image](https://hobbycomponents.com/images/forum/mLink/mLink_DHT22_Connection_Diagram.png)
![Image](https://hobbycomponents.com/images/forum/mLink/mLink_Arduino_Connection_Table.png)
Raspberry Pi Connection Diagram
![Image](https://hobbycomponents.com/images/forum/mLink/mLink_DHT22_Raspberry_Pi_Diagram.png)
Please note: when connecting to a Raspberry Pi the mLink module should either be powered via 3.3V, or the mLink modules I2C pullup resistors should be removed. See the 'Removing the modules I2C pullup resistors' section below for more information.
Removing the modules I2C pullup resistors
Please note that the modules I2C pullup resistors should be removed if you intend to use it as follows:
1) You wish to connect more than 5 modules to the same I2C bus.
2) You wish to power this module at 5V and you have a 3.3V development board that does not have a 5V tolerant I2C interface.
3) You wish to power this module at 5V and you have a 3.3V development board that has its own I2C pullup resistors.
To disconnect the modules two 10K pullup resistors from the I2C bus, locate the 3 jumper pads labelled ‘END DEV’ and cut the two tracks linking them together as follows:
![Image](https://hobbycomponents.com/images/forum/mLink/mLink_HCMODU0181_Pullups.png)
![Image](http://hobbycomponents.com/images/forum/forum/Downloads.png)
mLink Arduino library
viewtopic.php?f=58&t=3001
mLink Raspberry Pi Python module
The mLink python module can be installed with the following terminal command:
- pip install hc-mlink
Alternatively the library can be manually installed by downloading it from the forum and unzipping it to your project folder. See the Python module forum thread for more information and download link:
viewtopic.php?f=131&t=3062&p=8592#p8592
Please note that in some cases there may be additional configuration required. If you have issues getting your Raspberry Pi to communicate with the mLink module then please see the Python module forum thread here: viewtopic.php?f=131&t=3062
mLink Library Quick Start Guide For Arduino Users
https://hobbycomponents.com/downloads/m ... _Guide.pdf
mLink Library Reference Guide For The DHT22 Module
https://hobbycomponents.com/downloads/m ... _Guide.pdf
mLink Specifications and Register Map For The DHT22 Module
https://hobbycomponents.com/downloads/m ... er_Map.pdf
Libraries, example code, and diagrams are provided as an additional free service by Hobby Components and are not sold as part of this product. We do no provide any guarantees or warranties as to their accuracy or fitness for purpose.
Descriptions and diagrams on this page are copyright Hobby Components Ltd and may not be reproduced without permission.