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Temperature and Humidity Sensor: AHT21

  • £350

This is a high-precision intergated temperature and humidity sensor module for use with your Arduino or micrcontroller project.

It has an I2C interface so is easy to communicate with & Arduino libraries are available. Note: There is only one I2C address so it's not a good option when you need multiple humidity sensors on one I2C bus.

It's great for your environemental monitoring projects, maybe measuring temperature and humidity in your greenhouse or for weather monitoring.

The specifications are:

  • Voltage supply: 2.2 - 5.5V DC
  • Temperature range: -40 to 120
  • Temperature accuracy: ± 0.3 ℃
  • Humidity range: 0-100%
  • Humidity accuracy: ± 2 % RH ( 25 ℃)
  • Communication: I2C
  • Sensor IC: AHT21

You get a 4 way header pin which you may want to solder on to use jumper wires, or add four wires to connect to your project.

Sensor details from the manufacturer are here.

The datasheet can be downloaded here.

There is an Arduino library for communicating to these devices here. There are others! I needed to download that library. Then I opened up the folder and zipped up the "AHT-main" folder. This can then be added to your Arduino libraries by "Include Library" -> "add .ZIP library" and then select the zipped "AHT-main" folder.

Here is a brief sketch to get you up and running.

The connections are:

  • Sensor: VIN to Arduino: +5V
  • Sensor: GND to Arduino: GND
  • Sensor: SCL to Arduino: A5 (I2C Clock)
  • Sensor: SDA to Arduino: A4 (I2C Data)

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