Attributes

Brand	-
Category	Robotics / STEM Teaching Tools / Sensors
Origin	-
Sensor Type	HTU21D Digital Humidity & Temperature
Interface	I2C (Inter-Integrated Circuit)
Operating Voltage	3.3V to 5.5V DC
Humidity Range	0% to 100% RH
Temperature Range	-40°C to +125°C
Humidity Accuracy	±2% RH (at 25°C)
Temperature Accuracy	±0.3°C (at 25°C)
Response Time	5 seconds (typical)
Board Dimensions	14mm x 9mm x 2mm
Package Includes	1x GY-21 Module, 1x Pin Header Strip

6 reviews

Anonymous

Mar 31, 2026

Rating: 5/5

Perfect for Arduino Projects

This sensor module works flawlessly with my Arduino Uno. The I2C library integration was straightforward, and the readings are consistent with my calibrated reference meter. Great value for hobbyists.

Anonymous

Mar 31, 2026

Rating: 5/5

High Precision at Low Cost

Compared to more expensive industrial sensors, this HTU21 module offers impressive accuracy for the price point. Ideal for prototyping environmental data loggers.

Anonymous

Mar 20, 2026

Rating: 4/5

Solid Performance

We bought a batch of ten for our makerspace. Nine worked perfectly out of the box; one had a slightly loose pin header but was easily fixed. Overall very satisfied with the quality.

Anonymous

Mar 18, 2026

Rating: 4/5

Reliable for Plant Monitoring

I used three of these to monitor humidity in my indoor garden. They have been running for two months without drift. Only giving 4 stars because the soldering pads are a bit small for beginners.

Anonymous

Mar 04, 2026

Rating: 5/5

Great for University Projects

Bought this for my final year project on smart home automation. The documentation online is plentiful, and the sensor responds quickly to changes in humidity. Highly recommended.

Anonymous

Mar 04, 2026

Rating: 5/5

Low Power Consumption

Excellent choice for battery-powered IoT nodes. The sleep mode current draw is minimal, allowing my weather station to run for weeks on a single charge.

5 FAQ

Q: What is the default I2C address for this sensor?

A: The default I2C address for the HTU21D sensor on this module is typically 0x40. However, please verify with your specific library documentation as some variations exist.

Q: Is this module compatible with 5V logic levels like the Arduino Uno?

A: Yes, the GY-21 module includes a voltage regulator and level shifting, making it safe to use with both 3.3V and 5V microcontrollers.

Q: Does the package include connecting wires?

A: The package includes the sensor module and a strip of male pin headers for soldering. Connecting wires are not included but can be purchased separately.

Q: How do I calibrate the sensor if the readings seem off?

A: The HTU21D is factory calibrated and generally does not require user calibration. If readings are inconsistent, check your power supply stability and ensure proper I2C pull-up resistors are installed.

Q: Can this sensor be used outdoors in direct rain?

A: No, this module is not waterproof or weather-sealed. It should be housed in a breathable enclosure if used outdoors to protect it from direct moisture and dust.

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