Goal
Create arduino based 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 and voltages
to devide between multiplexers
| Sensor | address | alt address | spec | Vmin-Vmax | Vtyp | 3.3v | 5v |
|---|---|---|---|---|---|---|---|
| Senserion SHT2x | 0x40 (64) | 0x41 (65) | 20,21,25 | 2.1-3.6v | 3v |  |  |
| Senserion SHT3x | 0x44 (68) | 0x45 (69) | SHT3x | 2.15-5.5v | 3.3v | | |
| Senserion SHT8x | 0x44 (58) | SHT85 | 2.15-5.5v | 3.3v | | | |
| Meas(1) HTU21D | 0x40 (64) | HTU21D | 1.5v-3.6v | 3v | | | |
| Silicon Labs Si7021 | 0x40 (64) | 1.9v-3.6v | - | | | ||
| Bosch(2) BMEx80 | 0x76 (118) | 0x77 (119) | 680 | 1.71v-3.6v | 1.8v | | |
| Bosch(2) BME280 | 0x76 (118) | 0x77 (119) | 280 | 1.71v-3.6v | 1.8v | | |
| Ti(3) HDC1080 | 0x40 (64) | 2.7v-5.5v | 3v | | | ||
| AOSONG DHT12 | 0x5C (92) | 2.7-5.5v | 5v | | | ||
| AOSONG AM2320 | 0x5C (92) | 0xB8 ? | 3.1-5.5v | 5v | | |
1 TE Connectivity Measurement Specialties
2 Texas Instruments
3 Bosch Sensortec
Versions
v1
- Single multiplexer breadboard draft project with 26 Sensors
v2
- Use less wires and more soldering and connectors
Plan
v2
- Add more multiplexors to be able to include hdc1080 and Si7021,
- Add more SHT85 sensors to see results repitability (for most expensive sensor)
- Add more columns to the screen
v3
- Power one of multiplexers by 5v to add DHT22 to test.
- SD data logging and visualisation
v4
- remove libraries (that is suppose to work with single sensor mostly) and create simple init and read functions for all sensor types
- remove i2c scan every cycle, remember sensors from setup phase (need restart to change sensors but it is fine)
- add non-i2c sensors like DHT11 and AM2302
- make some additional screen modes and control buttons
v5
- got some kind of home-made "calibration" tests with resolutions
- publish final electric scheme, sketch, results
