Description
Reviews
| Brand | - |
| Category | Robotics / STEM Teaching Tools / Sensors |
| Origin | - |
| Model Number | CJ-HJ31A / HR202L |
| Sensor Type | Resistive Humidity Sensor |
| Operating Voltage | DC 1.5V - 5V |
| Humidity Range | 20% RH to 90% RH |
| Response Time | < 10 seconds |
| Recovery Time | < 30 seconds |
| Accuracy | ±5% RH (at 25°C) |
| Operating Temperature | -10°C to +60°C |
| Package Style | Through-hole / Module |
| Application | Home Automation, Weather Stations |
Anonymous
Mar 31, 2026
Rating: 5/5
Great documentation support
Found plenty of libraries online compatible with this HR202L chip. Integration with ESP32 was seamless. The output is analog which gives good resolution.
Anonymous
Mar 28, 2026
Rating: 4/5
Good sensitivity, needs calibration
The module is very responsive to breath or steam. You do need to spend some time calibrating it against a known standard if you need precise data, but for general detection, it's excellent.
Anonymous
Mar 20, 2026
Rating: 3/5
Decent but fragile
The sensor works fine, but the pins bent easily during shipping. Make sure to handle with care. Once set up, it reads humidity changes accurately enough for my alarm system.
Anonymous
Mar 20, 2026
Rating: 4/5
Works well for plant monitoring
Using this to monitor soil ambient humidity in my greenhouse setup. It reacts quickly when I mist the plants. The only downside is the lack of a waterproof coating on the bare element.
Anonymous
Mar 17, 2026
Rating: 5/5
Reliable and compact
I bought five of these for different rooms. They are small, easy to solder, and have been running stable for three months now. Highly recommended for DIY enthusiasts.
Anonymous
Mar 08, 2026
Rating: 5/5
Perfect for my Arduino project
This sensor works exactly as described. The resistance changes smoothly with humidity levels, making it easy to calibrate in code. Great value for the price.
Q: Does this module come with a digital output or just analog?
A: This specific CJ-HJ31A module provides an analog output based on resistance change. You will need an ADC (Analog-to-Digital Converter) on your microcontroller to read the values.
Q: Is there a library available for Raspberry Pi?
A: Since the output is analog, you cannot connect it directly to GPIO pins on a Raspberry Pi. You must use an external ADC chip like the MCP3008, for which many Python libraries exist.
Q: How long does it take to stabilize after powering on?
A: Typically, the sensor requires a warm-up period of about 1 to 2 minutes after power-on to provide stable and accurate readings.
Q: Can this be used outdoors in the rain?
A: No, this sensor is not waterproof. It should be used in indoor environments or inside a weatherproof enclosure with ventilation to allow air exchange.
Q: What is the maximum voltage I can apply without damaging the sensor?
A: We recommend operating between 1.5V and 5V DC. Applying voltage higher than 5V may damage the sensitive resistive element permanently.
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