Bộ Dụng Cụ Kiểm Tra Khoảng Cách Cồn Mq3 Mq3

Function: the alcohol concentration alarm circuit is mainly an alarm control circuit consisting of mq-3 of the gas sensitive sensor group. when the sensor mq-3 is located in an environment where alcohol vapor exists, the conductivity of the sensor will increase with the increase of alcohol vapor concentration.The alcohol content in the environment can be determined by measuring the series pressure between the sensor and the fixed resistance.

Working voltage: 5-7.5v dc

Pcb size: 6.2x3.6 cm



Circuit description:

This circuit can be powered by 5-7.5 volt dc power source,Switch s1 for power switch,Resistance r1 and led d1 for power supply instructions,Sensor mq-3 interior needs to be heated to a certain temperature at work,So there is an electric wire inside it,Resistance r4 is the limiting resistance of electric wire,Mq-3 fever is normal after electricity transmission.When mq-3 does not detect alcohol vapor, its internal resistance is high, r3, rw pressure drop is low, ne55's 2-foot voltage is lower than the trigger voltage (vcc/3), its 3-foot output is high, d2 is extinguished, buzzers are silent and relays are not moving.When mq-3 detects alcohol vapor, the internal resistance drops, the voltage of r3 and rw increases, the voltage of ne55 at 2 feet is higher than the trigger voltage, 3 feet becomes low-level, d2 leads light, buzzers start to sound through currents, and electromagnetic coils in relays attract switches.Thus, the detection and alarm function is realized.Adjustable resistance rw is used to adjust detection sensitivity.This circuit uses the second comparator inside ne 555 to detect voltage changes and use its internal trigger to shake off.Ne 55's 7th and 5th feet are not in use and are suspended.The output side of the relay, j3, can be used to control other electrical appliances, such as fan exhaust, to start fan exhaust when alcohol concentration exceeds standard, to close fan exhaust after concentration drops, and to achieve automatic control.Diode d 3 is used to eliminate inductive electric potential generated by relay coil breaking.The power supply interface can be dc plug, or can be used directly in j2 position, pay attention to the positive and negative pole sign, dc plug power supply positive and nega