Goal
Arduino device to compare data for as much t/RH sensors as possible without manual sensor switch
Preparation
Use of same sensor on i2c usually limited by 1 or 2 (using ALT i2c address) of same type. And SHT20, SHT21, SHT25, HTU21 is actually same type, so to be able to compare measurement there is need to use i2c multiplexer. In case of 8 line multiplexer there is possibility to have 8-16 sensor of same time to be connected with Arduino.
Sensor i2c addresses
| Sensor | address | alt address | spec | V | ||
|---|---|---|---|---|---|---|
| Senserion SHT2x | 0x40 | 64 | 0x41 | 65 | 20,21,25 | 3.3v |
| Senserion SHT3x | 0x44 | 68 | 0x45 | 69 | SHT3x | 3.3v |
| Senserion SHT8x | 0x44 | 68 | 69 | SHT85 | 3.3v | |
| Meas(1) HTU21D | 0x40 | 64 | HTU21D | 3.3v | ||
| Silicon Labs Si7021 | 0x40 | 64 | 3.3v | |||
| Bosch(2) BMEx80 | 0x76 | 118 | 0x77 | 119 | 280,680 | 3.3v |
| Ti(3) HDC1080 | 0x40 | 64 | 3.3v | |||
| AOSONG DHT12 | 0x5C | 92 | 3.3v | |||
1 TE Connectivity Measurement Specialties
2 Texas Instruments
3 Bosch Sensortec
Multiplexer Lines
| Line | 0x40 | 0x44 | 0x5c | 0x77 | 0x41 | 0x45 | 0x76 | 0x70 |
|---|---|---|---|---|---|---|---|---|
| A | SHT21 | SHT30 | DHT12 | BME680 | ||||
| B | SHT21 | SHT30 | DHT12 | BME680 | ||||
| C | HTU21D | SHT31 | DHT12 | BME280 | ||||
| D | HTU21D | SHT31 | - | BME280 | ||||
| E | HTU21D | SHT35 | - | BME280 | ||||
| F | SHT20 | SHT35 | - | BME680 | ||||
| G | SHT21 | SHT31 | - | BME680 | ||||
| H | SHT25 | SHT85 | - | - |
i2c Scan
Port:0 i2c addr 64 i2c addr 68 i2c addr 119 Port:1 i2c addr 64 i2c addr 68 i2c addr 119 Port:2 i2c addr 64 i2c addr 68 i2c addr 118 Port:3 i2c addr 64 i2c addr 68 i2c addr 118 Port:4 i2c addr 64 i2c addr 68 i2c addr 118 Port:5 i2c addr 64 i2c addr 68 i2c addr 92 i2c addr 118 Port:6 i2c addr 64 i2c addr 68 i2c addr 92 i2c addr 118 Port:7 i2c addr 64 i2c addr 68 i2c addr 92
Hardware in use
- Mega2560 keyestudio
- LCD 3.5 inch Arduino Mega2560
- DFRobot i2c multiplexer (or compatible ShangSi MoudleCX TCA9548A i2c multiplexer)
- Sensors (DHT11, SHT21, SHT20, SHT25, HTU21D, SHT30, SHT31, SHT35, SHT85, BME280, BME680)
Draft sketch
github code:
