Application Guide for Sharp A1DU5P2CP005B VOCs Sensor Module - sharpsensoruser/sharp-sensor-demos GitHub Wiki
Sharp A1DU5P2CP005B VOCs Sensor Module Application Guide
A1DU5P2CP005B is a new sensor module from Sharp Corporation for measuring the concentration of harmful substances in the air such as formaldehyde (HCHO) and TVOC (Total Volatile Organic Compounds). The sensor module incorporates the iS-MM-VOCs-4 sensor IC made by MNST (Micro & Nano Sensor Technology Co., Ltd). Typical applications of A1DU5P2CP005B include:
- Air purifiers and air conditioners
- Smart home and room monitoring devices
- Air quality monitors
- Portable / wearable devices
MSNT iS-MM-VOCs-4 is a very compact MEMS sensor (3.8 x 3.8 x 1.5mm) which is capable of detecting formaldehyde, CO2, ethanol, and TVOC. In collaboration with MNST, Sharp has released A1DU5P2CP005B as a specific configuration of the sensor in module packaging which can sense 2 of the 4 substances: formaldehyde and TVOC. Other configurations of the sensor are possible and if you are interested in volume production you can contact Socle Technology Corp. which is Sharp's agent in North America, China, and Taiwan.
You should be able to find the Sharp module at a component distributor under part number A1DU5P2CP005B.
Sharp A1DU5P2CP005B is designed to be used indoors. Follow the module specifications and avoid exposing the sensor to dust, salt, or gases such as SO2, H2S, Cl2 and NH3.
When the module is first powered on, it goes through a pre-heating initialization period lasting up to 3 minutes.
Communication with the A1DU5P2CP005B module can be done over I2C or UART (serial). In either case, the module transmits a 9-byte data record with the following format.
The module outputs the HCHO and TVOC values using units of ppb (parts per billion). However, air quality concentrations are commonly expressed in units of ug/m3. The conversion from ppb to ug/m3 depends on atmospheric pressure, temperature, and the molecular weight of the substance involved. According to this reference, if we assume a standard pressure of 1 atmosphere and a temperature of 25 degrees Celsius, the formula for converting ppb to ug/m3 units is as follows:
Concentration (ug/m3) = 0.0409 x concentration (ppb) x molecular weight
In the case of formaldehyde (HCHO), the molecular weight is 30 g/mol. So no problem with formaldehyde.
However, TVOC is a combination of several different VOC substances such as benzene and toluene. So how to determine what molecular weight to use? I contacted the sensor manufacturer MNST directly and put this question to them. They told me that for TVOC, to use a conversion factor of 1.8:
1 ppb = 1.8 ug/m3
Working backwards using the first formula, I found that this corresponds to a molecular weight of 44 g/mol which is quite close to the molecular weight of propane (44.1 g/mol). So I am guessing that MNST derived this 1.8 factor based on propane although I am not entirely certain because while propane is a VOC as well, it is not commonly found in typical indoor environments.
Sharp A1DU5P2CP005B uses a 6-pin connector made by Zhejiang Xinfuer Electronics Co., Ltd.:
- Module-side connector: 1.25T-6AWB
Connect the A1DU5P2CP005B sensor module to your Arduino board as shown in the figure below. This example uses Arduino Uno but it should work the same with Arduino Mega 2560. The sensor module requires a supply voltage of 3.3V and its SDA and SCL pins operate on 3.3V logic as well. Therefore, it is necessary to use a logic level converter to convert between 3.3V and the 5V that Arduino uses.
The corresponding I2C demo source code for the above circuit uses the Arduino Wire library to request the formaldehyde and TVOC concentration data from the sensor over I2C, and then display both values using the Arduino Serial Monitor.
The I2C slave address for the module is 0x51 and the register for requesting the 9-byte data record is 0x61.
Connect the A1DU5P2CP005B sensor module to your Arduino board as shown in the figure below. This example uses Arduino Uno but it should work the same with Arduino Mega 2560.
In the circuit, the hardware serial port is used only for printing output concentration values to the Arduino Serial Monitor. A software serial port is used for the actual communication with the A1DU5P2CP005B module (Arduino pins 10 and 11) as shown in the UART demo source code. If you're using Arduino Mega, you can use one of the other hardware serial ports instead such as Serial1 for communicating with the A1DU5P2CP005B module.
The sensor module requires a supply voltage of 3.3V and its TX and RX pins operate on 3.3V logic as well. Therefore, it is necessary to use a logic level converter to convert between 3.3V and the 5V that Arduino uses.
The UART demo source code shows how to request the concentration data from the sensor by sending the UART command 0x61. A 9-byte data record is transmitted back by the sensor module which is then decoded into concentration values and printed to the Arduino Serial Monitor.
If you are switching between different Arduino boards, make sure you go to the Arduino IDE Tools menu and set Board and Port appropriately before compiling or uploading the code. The following screen capture shows example output from the A1DU5P2CP005B module as displayed on the Arduino Serial Monitor.
To actually test with some VOCs, you can open the cap of a permanent marker and wave it around near the sensor.