Temperature is the measure of warmth or coldness in reference to a set standard, often expressed in terms of degrees Fahrenheit or Celsius. Humidity refers to the amount of water vapor, or moisture, in the air.
There are generally two types of humidity ie. absolute and relative. The former tells the humidity present in a parcel of air without taking temperature into consideration whereas the latter tells the humidity present in the air concerning the temperature of the air.
If temperature increases it will lead to a decrease in relative humidity, thus the air will become drier whereas when temperature decreases, the air will become wet means the relative humidity will increase.
Temperature and humidity sensor are devices that can convert temperature and humidity into electrical signals that can easily measure temperature and humidity. Temperature humidity transmitters available on the markets, generally measure the amount of temperature and relative humidity in the air, and convert it into electrical signals or other signal forms according to certain rules and output the signal to the instrument or software to meet the environmental monitoring needs of users.
An overview of the SHT35 sensor
SHT3x-DIS is the next generation of Sensirion’s temperature and humidity sensors. It builds on a new CMOSens sensor chip that is at the heart of Sensirion’s new humidity and temperature platform. Its functionality includes enhanced signal processing, two distinctive and user selectable I2C addresses and communication speeds of up to 1 MHz. These sensors are made in DFN package and this allows for integration of the SHT3x-DIS into a great variety of applications. Additionally, the wide supply voltage range of 2.4 V to 5.5 V guarantees compatibility with diverse assembly situations.
SHT35 module Key Features
- User-selectable module power supply voltage between 3V3 and 5V
- Selectable I2C address
- Access to Reset pin of SHT35
- ON/OFF LED indicator
- GebraBit Pin Compatible with GEBRABUS
- It can be used as a daughter board of GebraBit MCU Modules
- Featuring Castellated pad (Assembled as SMD Part)
- Separatable screw parts to reduce the size of the board
- Package: GebraBit small (36.29mm x 32.72mm)
GebraBit SHT35 module
GebraBit SHT35 is a digital humidity and temperature measurement module.
GebraBit SHT35 operates with 3V3 and 5V Supply Voltages that users can easily select with jumper selector of the module.
User can interface with GebraBit SHT35 by I2C protocol and capable of setting I2C address with jumper selector of the module.
Also, Users can access to the most important pins of the SHT35 through the GebraBit SHT35 module. Reset (RST) and interrupt (int) Pins that can user use them as reset the module and interrupt to indicates programmable alarm condition of sensor
Considering that it is difficult to access the sensor pins, the user needs a starter circuit and driver for the hardware development and of course the software development of the HTU31D sensor. GebraBit implements the HTU31D sensor circuit and provides access for the convenience of users.
It is enough to put the GebraBit SHT35 module in the BreadBoard, then by applying the proper voltage set up the GebraBit SHT35 module with any of Arduino, Raspberry Pi, Discovery board, and especially we recommend using GebraBit microcontroller development modules (GebraBit STM32F303 or GebraBit ATMEGA32 module) then receive the data.
The reason for our recommendation when setting up the GebraBit SHT35 module with GebraBit microcontroller development modules (such as GebraBit STM32F303 or GebraBit ATMEGA32), is the presence of an internal 3V3 regulator on these modules and the compatibility of the pin order of all GebraBit modules together (GEBRABUS standard), it’s enough to Put the SHT35 in the corresponding socket as shown in the above picture and develop the desired sensor module without the need for wiring.
Introduction of module sections
SHT35 sensor is the Humidity and Temperature sensor of this module which its circuit is designed.
According to the state of 0R resistance of this jumper, the main voltage of the sensor power supply is selected between “5V” and “3V3”.
SHT35 series has the capability to respond 2 distinct I²C addresses. This feature allows to use multiple sensors on the same I²C network and avoid address conflict with other components. The only constraint is that the level has to stay constant starting from the I2C start condition until the communication is finished. For this purpose, the ADD SEL selector jumper is installed on the GebraBit SHT35 module so that the user can easily change the I2C address of the sensor by changing the ADD SEL 0R resistance then users are able to use multiple sensors on the same I2C network.
The sensor I2C address table is as follows:
Power supply LED
According to the state of the VCC SEL jumper and applying voltage to the module by the corresponding pin, the LED of the module will be lit.
GebraBit SHT35 Module pins
- 3V3 and 5V: These pins can supply the sensor main power supply and the logic level of the sensor digital connection (I2C) according to the state of the VCC SEL selector jumper.
- GND: This is the common ground pin for power and logic level of the sensor.
- SDA: This pin is the I2C communication data pin, which is connected to the corresponding data pin in the microcontroller (processor). According to the state of the VCC SEL jumper, you can use the logic level with a voltage of 5V or 3V3.
- SCL: This pin is the I2C communication clock pin, which is connected to the corresponding clock pin in the microcontroller (processor). Depending on the state of the VCC SEL jumper, you can use the logic level with a voltage of 5V or 3V3.
- RST: The RST pin can be used to generate a reset of the sensor. A minimum pulse of 1 μs is required to reliably trigger a sensor reset.
- INT : Interrupt pin for SHT35 sensor, according to the datasheet , the user can set the interrupt conditions, the modes and methods of the interruption, etc.
Connect to the processor
I2C connection with GebraBit STM32F303
for i2c communication of GebraBit SHT35 and GebraBit STM32F303 microcontroller module, after defining SDA and SCL on pins PB9 and PB8 (for convenience in STMCUBEMX), follow the below steps:
- Connect the 3V3 pin of the SHT35 module to the 3V3 output pin of the microcontroller module. (red wire)
- Connect the GND pin of the SHT35 module to the GND pin of the microcontroller module (black wire).
- Connect the SCL pin of the SHT35 module to the PB8 pin of the microcontroller (SCL) module (blue wire).
- Connect the SDA pin of the SHT35 module to the PB9 pin of the microcontroller (SDA) module. (yellow wire)
Note: Considering that the PA14 pin of the GebraBit STM32F303 microcontroller module is used to program the microcontroller, I2C setting on the PA14 and PA15 pins is impossible in this version, so in this version for I2C connection with the GebraBit STM32F303 microcontroller module, GebraBit SHT35 module cannot be placed as Pin to Pin on it.
I2C connection with GebraBit ATMEGA32A
Considering that the I2C pins of the ATMEGA32A microcontroller are based on the GEBRABUS standard and correspond to the I2C pins of other GEBRABIT modules, the GebraBit SHT35 module can be placed pin to pin on the GebraBit ATMEGA32A module Here, for better understanding, the separate connection of these two modules is shown.
NOTE: If you are using GebraBit microcontroller modules, note that the power selector jumper of the GebraBit SHT35 is set to 3V3 so that you can easily power-on the GebraBit SHT35 module by getting the 3V3 voltage from the microcontroller module.
I2C Connection with ARDUINO UNO
follow the below steps to connect the GebraBit SHT35 module to the ARDUINO UNO:
- Since the VCC SEL jumper is set to 3V3, connect the “3V3” pin of the SHT35 module to the “3V3” output pin of the ARDUINO UNO board. (Red wire)
- Connect the SCL pin of the SHT35 module to the A5 pin of the ARDUINO UNO board (SCL). (blue wire)
- Connect the SDA pin of the SHT35 module to the A4 pin of the ARDUINO UNO board (SDA). (orange wire)
How to connect the above mentioned steps, can be seen in this picture: