CH07J alternative sensor module
This sensor module is a replacement for CH-07J-3D0A humidity sensor found in many dehumidifying units. It uses DHT20 sensor, delivers higher precision and supports wider measurement range.
Dehumidifier usually reports E3 error when this sensor module fails.
- Operating voltage: from 3 to 5 V DC
- PCB size: 34,0 x 21,5 mm, thickness: 1,6 mm
Data encoding
Data is transmitted over single wire and encoded with pulse-position modulation (PPM). After initial long high pulse of length of 524 ms a series of 32 pulses is transmitted.
- Most significant bit first (MSB first)
- Bit 0 is transmitted using a 500 µs low, 500 µs high pulse
- Bit 1 is transmitted using a 500 µs low, 1500 µs high pulse
- Total of 4 bytes are transmitted, each consisting of 8 bits
- The first byte encodes the temperature, in degrees Celsius (°C)
- The second byte encodes the relative humidity, in percentages (Rh%)
- The third byte is the first byte negated (complementary value), to detect transmission errors
- The fourth byte is the second byte negated, to detect transmission errors
Product images
SKU: CH07J
Schematics and source code
Sensor module uses ATmega328PB and gets humidity and temperature measurements from DHT20 sensor over I²C protocol. All parts except DHT20 and 3-pin JST PH 2 mm connector are placed on the back side of the PCB to be less exposed to the cold humid air.