Product Characteristics:
The gas-sensitive material used in the MQ-3 gas sensor is tin dioxide (SnO2) which has a low conductivity in clean air. When alcohol vapour is present in the sensor's environment, the conductivity of the sensor increases with the concentration of combustible gas in the air. Having different resistance values for different concentrations, the change in conductivity can be converted to an output signal corresponding to the concentration of that gas using a simple circuit. Resistant to interference from gasoline, smoke, and water vapour. This sensor detects a wide range of alcohol atmospheres at a variety of concentrations, making it a low-cost sensor suitable for a wide range of applications. Sensor ad hoc M3 fixed mounting holes, using a wide voltage LM393 comparator, clean signal, good waveform, strong driving ability, more than 15mA, with adjustable precision potentiometer to adjust the sensitivity.

Product parameters:
Operating voltage: 5VDC

Power consumption (current): 150mA

Output form: analogue and digital output

Instructions for use:
Connect VCC and GND, the module power indicator will light. Before use, the power supply at least 2 minutes to warm up, the sensor is slightly warm is a normal phenomenon, because there is an electric heating wire inside, if it is hot, it is not normal. Module in the absence of sensitive gas influence or gas concentration does not exceed the set threshold, the digital interface DO port output high level, analogue interface A0 voltage is basically 0v or so, when the gas influence exceeds the set threshold, the module digital interface D0 output low level, the digital indicator light, the analogue interface A0 output voltage will slowly increase with the influence of the gas, the AO output: 0.1-0.3V (relatively) AO output: 0.1-0.3V (non-polluting), the highest concentration of voltage 4V or so; clockwise adjustment of the potentiometer (only for the sensitivity of the TTL output) to sense the increase in concentration; small board digital output D0 can be directly connected to the microcontroller, through the microcontroller to detect the high and low levels, and thus detect the ambient gas; small board digital output DO can be directly driven by the shop relay module, which can be composed of a gas switch; small board digital output DO can be directly driven by the shop relay module, which can be composed of a gas switch; small board digital output D0 can be directly driven by the shop digital indicator light. The digital output DO can directly drive our active buzzer module, which can form a gas alarm; the analogue output AO can be connected with our AD module, through AD conversion, it can get the approximate value of ambient gas concentration.

Note:
Correct wiring! Do not reverse the positive and negative connections, so that the board electronics burned. The sensor probe sensitivity is non-linear, so the analogue output voltage is not linearly related to the sensitive gas concentration. This module does not have analogue output voltage concentration graph to provide, please according to the standard instrument actual comparison voltage concentration control value, the actual test distance from the sensitive source gas will exist in the concentration of different. 5.1ohm resistor in series with the heating circuit of the sensor, can protect the heating wire from the shock of the cold power-up.