Humidity Sensor HTU21D

Description

Things you should know about this sensor:

• Uses the I²C interface
• Typical humidity accuracy of ±2%
• Typical temperature accuracy of ±0.3C
• Operates from 0 to 100% humidity but this sensor isn’t recommended for harsh environments where it could come in contact with water (such as rain).
• 3.3V sensor – use inline logic level converters or 10k resistors to limit 5V signals
• Here’s the datasheet
• Only one HTU21D sensor can reside on the I²C bus at a time

This sensor is ideal for environmental sensing and data logging. Perfect for a weather station or humidor control system. It is a very good replacement for digital humidity sensors such as the SHT15, SHT21, SHT25, HIH-4030, HIH6130 and capacitive humidity sensors such as the HH10D.

Suggested Reading

Things you might need to know:

• I²C Protocol
• Using the PCA9306 voltage translator
• Logic Levels
• Installing an Arduino library

Connections: Breakout board to Arduino

• VCC → 3.3V
• GND → GND
• SDA → A4
• SCL → A5

There are only four pins that need to be hooked up in order to start using this sensor in a project. One for VCC, one for GND, and two data lines for I²C communication. On an Arduino board connect the SDA pin on the breakout board to A4 and SCL to A5. If you have a newer Arduino, you can connect the SDA and SCL lines directly to the SDA and SCL lines broken out on the Arduino headers.

This board runs at 3.3V. Be sure to power the board from the 3.3V pin! Because I²C is an open drain signal, there’s no need to worry about level shifting the signal; the 3.3V signal will be adequate to communicate with the Arduino and the signal will never reach a dangerous level for the pins on the HTU21D.

• Note: This breakout board has built in 4.7k pull up resistors for I²C communications. If you’re hooking up multiple I²C devices on the same bus, you may want to disable these resistors