Crowtail- HTU21D Humidity& Temperature Sensor
Description¶
Crowtail- HTU21D Humidity &Temperature sensor is a low-cost, easy to use, highly accurate, digital humidity and temperature sensor. And the work voltage range about this sensor is 1.5V-3.6V, so we need to use the AMS1117 to achieve step-down when we want it work with our crowduino which has a 5V voltage output. The sensor outputs the calibrated digital signal in standard I2C format. Diversified output mode, wide operating voltage range, while high temperature accuracy and humidity accuracy. HTU21 series module designed for low-power/small-volume application design, with good quality, fast response speed, anti-interference ability, cost-effective advantages, very low power consumption. It’s ideal for environmental sensing and data logging and perfect for a weather stations or humidor control systems. All you need is connect the specific crowtail port into the arduino/crowduino by using a crowtail cable.
Model: CRT02120H 
Specifications¶
| Item | Value |
|---|---|
| Input voltage | 5V |
| Humidity measurement range | 0-100% RH |
| Temperature measurement range | -40 ℃ -105 ℃ |
| Maximum power consumption | 2.7uW |
| Communication | I2C |
| Humidity accuracy range (10% RH to 95% RH) | HTU21D ± 2% RH |
| Load Weight | 1KG |
| Humidity hysteresis | ± 1% RH |
| Measurement time | 50ms |
| Annual drift | -0.5% RH / year |
| Response time | 5s |
| Dimensions(mm) | 20.0(L)x20.0(W)x9.8(H) |
Interface¶
Platforms Supported¶
| Arduino |
|---|
 |
Usage¶
Hardware¶
STEP1 Prepare the below stuffs:
| Crowduino Uno | Base Shield | Crowtail- HTU21D Humidity &Temperature sensor |
|---|---|---|
 |  |  |
| Get one now | Get one now | Get one now |
STEP2 Plug Crowtail-Base Shield into Crowduino Uno;
STEP3 Plug HTU21D Humidity&Temperature Sensor into I2C port on the Crowtail-Base Shield I Port with Crowtail cable;
STEP4 Connect Crowduino Uno to PC via a Mini USB cable.
| NOTE |
|---|
| If we don't have Crowtail Base Shield, We also can directly connect this module to Crowduino Uno as below. |
| Crowduino Uno | Weight Sensor |
|---|---|
| A4(J7) | SDA |
| A5(J7) | SCL |
| 5V | VCC |
| GND | GND |
Software¶
STEP 1.Download filesSparkFun_HTU21D_Breakout_Arduino_Library-master.zip
STEP2 Configure controller board&communication port
On top of the Arduino IDE, click “Tools>Board>” and select “Arduino Uno” from the available options
Select the COM port that indicates Arduino Uno. Please note that the actual numbers after the “COM” word will vary from computer to computer, so they could be different from the ones shown in the figure.
STEP 3 Install Library: Unzip the SparkFun_HTU21D_Breakout_Arduino_Library-master.zip file and copy it to the Libraries directory under the Arduino installation directory
STEP4 Open Arduino IDE and load SparkFun_HTU21D_RegisterReading：click “File→Examples→SparkFun HTU21D Humidity and Temperature Sensor Breakout→SparkFun_HTU21D_RegisterReading”
STEP5 Click the 
to upload the code to the Crowduino board
STEP6 After the program is downloaded, open the Serial Monitor of Arduino IDE, set baud rate to 9600, and the value of humidity and temperature will be printed,such as shown in the figure 
FAQS¶
You can list you question here or contact with techsupport@elecrow.com for technology support.
Resources¶
Crowtail-_HTU21D_Humidity%26Temperature_Sensor_eagle_file.zip
SparkFun_HTU21D_Breakout_Arduino_Library-master.zip
HTU21D_datasheet.pdf