Template: SGP40 VOC Senosr Spec
Introduction
The SGP40 VOC Sensor is a digital VOC (Volatile Organic Compounds) sensor module that incorporates SGP40, designed for air quality monitoring. It can be used to measure fire coal, natural gas emissions, cigarette/cooking smoke, and emissions from construction activity, decoration material, furniture, and home appliances, then generate digital signals for triggering air treatment devices. The SGP40 VOC Sensor is small in size for easy integration into air treatment devices and air quality monitors, definitely an ideal choice for learning air quality monitoring.
Feature
- Incorporates SGP40, for measuring 0 ~ 1000 ppm of ethanol equivalents.
- Features humidity-compensation and low heat dissipation, providing outstanding performance in all sorts of environments.
- Digital I2C output, less interference.
- Onboard voltage translator, compatible with 3.3V/5V operating voltage.
Specification
- Sensor: SGP40
- Measurement range: 0~1000 ppm of ethanol equivalents
- Communication bus: I2C (constant address: 0x59)
- Operating voltage: 3.3V/5V
- Response time: <10s (tau 63%)
- Switch-on time: <60s
- Dimensions: 27 x 20mm
- Mounting hole size: 2.0mm
Pinout
- Pins
| PIN | SYMBOL | Description |
| 1 | VCC | 3.3V/5V Power on |
| 2 | GND | Ground |
| 3 | SDA | I2C data pin |
| 4 | SCL | I2C clock pin |
Hardware
Controller
This product uses Sensirion's SGP40 gas sensor and is designed for easy integration into air purifiers or demand-controlled ventilation systems. Sensirion's CMOSens® technology provides a complete, easy-to-use sensor system on a single chip with a digital I2C interface and temperature-controlled micro-heating plates that provide VOC-based humidity-compensated indoor air quality signals. Sensirion's powerful VOC algorithm processes the output signal directly, converting the original signal into a VOC index that can be used as a reliable measure of indoor air quality. The VOC algorithm automatically ADAPTS to the environment in which the sensor is located. Both the sensing element and the VOC algorithm are unmatched in robustness against the polluting gases present in real-world applications, resulting in unique long-term stability and low drift and device-to-device differences.
Communication protocol
SGP40 uses I2C communication, I2C communication, one data line, and one clock line. Normal I2C bus has three types of signals in the data transmission process: start signal, end signal, and response signal, as shown in the figure below:
Start signal: When SCL is high, SDA jumps from high level to low level, and data transmission begins。
End signal: When SCL is high, SDA jumps from low level to high level, and data transmission ends。
Reply signal: After receiving 8bit data, the receiving IC sends a specific low-level pulse to the sending IC to indicate that the data has been received..
- I2C data read and write operations for SGP40
As can be seen from the figure above, the data of SGP40 is sent with 16-bit addresses, and the 16-bit data sent needs a CRC-8/MAXIM verification code.
CRC
Cyclic Redundancy Check (CRC) is one of the most commonly used error Check codes in the field of data communication. Its characteristic is that the length of information fields and verification fields can be arbitrarily selected. Cyclic redundancy check (CRC) is a data transmission error detection function that performs polynomial calculations on the data and attaches the results to the back of the frame. The receiving device also performs a similar algorithm to ensure the correctness and integrity of the data transmission.
SGP40 uses THE CRC-8/MAXIM check code calculation, that is, the calculation result of polynomial x^8 + x^5 + x^4 + 1.
The procedure has been simplified, using the lookup table method.