Acetone sensor module

acetone sensor module is a module developed using MEMS micro gas sensor, which can be used to detect the acetone content in breath.

Feature:

High sensitivity, high resolution, low power consumption, and long service life. Providing UART, analog voltage signal, PWM waveform and other output methods with high stability and excellent linear output.

Application:

breath tester etc …

1. Technical Parameters

2. Module Size

3.    Pin definition

Remarks: Unused pins can be added according to the actual needs of users, such as buzzer, relay, solenoid valve and other output signals .

4. UART communication setting parameters

General settings: Use UART communication interface, the settings are as follows, Table 1:

The communication is active uploading, and the data is sent every 3S. The format of active data sending is hexadecimal, the format is as follows,

The data length reported by the module serial port is fixed at 24 bytes, and the current valid bits are: Frame header (0xAA) + temperature (4 bytes) + humidity (4      bytes) + voltage 1 + voltage 2 (reserved) (both voltages are 4 bytes) + gas type (1 byte) + gas concentration (4 bytes) + alarm/level (1 byte) + the 24th byte is fixed as a cumulative check code When 4 bytes of data such as temperature, voltage,   concentration, etc. are parsed into decimal system in hexadecimal system, The high   order of the original data is at the back, and the low order is at the front. After rearrangement, it is converted into a decimal integer, then divided by 1000 to get a decimal floating point number.

Examples:

AA A8 61 00 00 50 C3 00 00 DC 02 00 00 00 00 00 00 0B 20 4E 00 00 01 1E

Frame header    AA

Temperature    A8 61 00 00 --> 61 A8 (hexadecimal) -> 25000 (10 hex)-> 25.000 (divide by 1000)

Humidity    50 C3 00 00    -> C3 50    -> 50000    -> 50.000

Voltage 1    DC 02 00 00    -> 02 DC    -> 732    -> 0.732

Voltage 2 (reserved)    00 00 00 00       -> 0

Gas type    0B             -> 11

Gas concentration    20 4E 00 00    -> 4E 20       -> 20000    -> 20.000

Alarm level      01

Inspection code (cumulative)    1E

The analysis procedure of the cumulative check code (including the frame header) is as follows:

uint8_t CheckSum(uint8_t *p,uint8_t len)

{

uint8_ti;

uint32_t sum = 0;

for(i = 0;i < len;i++)

{

sum += p[i];

}

sum = sum & (0xFF);

return sum;

}

Serial commands:

The module can send commands through the serial port to achieve some functions, as follows:

(1) AA 00 FA

Switch the module to Q&A mode or active upload. The module initializes the default active upload mode. This command can be used to switch between the two modes .     (2) AA 00 F9

In the question and answer mode, the module data is fetched by this command, and the data return format is consistent with the active upload format.

(3) AA 00 FE BB Algorithm reset

(4) AA 00 FB

Toggle decimal floating point outpu

The decimal output format is as follows:

Note: The data is sent as a string, with spaces between the data.

Notes:

1. Conditions that must be avoided

1.1 Exposure to volatile silicon compound vapors

The module should be protected from silicon adhesive, hair gel, silicone rubber, putty or other places where volatile silicon compounds are present. Otherwise it will cause the sensitivity of the module is reduced and it will not even respond.

1.2 Highly corrosive environment

The module is exposed to high-concentration corrosive gases (such as H2S, SOX, Cl2, HCl, etc.), which will cause corrosion or damage to the sensor heating materials and   sensor leads in the module ，and it will cause irreversible deterioration of the performance of sensitive materials, which will affect the performance and accuracy of the module.

1.3 Contact with water

If the sensor in the module is splashed or immersed in water, it will cause the sensor's sensitivity characteristics to decrease and affect the measurement accuracy of the module.

1.4 Icing

The icing on the surface of the sensor's sensitive material of the module will cause the sensitive layer to crack and lose its sensitive characteristics.

2 Conditions to avoid as much as possible

2.1 Condensate

Under indoor use conditions, slight condensation will have a slight impact on the performance of the sensor in the module. But if water condenses on the surface of the sensitive layer and keeps it for a period of time, the sensor characteristics in the module will decrease, and the measurement error of the module will increase.

2.2 in high concentration gas

Regardless of whether the module is powered on, long-term placement in high concentration gas will affect the sensor characteristics in the module. If spraying directly with lighter gas to the sensor in the module, it will cause great damage to the sensor in the module, and will cause the sensitivity of the module to decrease.

2.3 Long-term storage

When the module is stored for a long time without power, the resistance of the sensor will have a reversible drift. This drift is related to the storage environment. Modules  should be stored in sealed bags that do not contain volatile silicon compounds .