I have done my project on alcohol detection for drivers, but I don't know the minimum and maximum distances between the alcohol sensor and the driver. What are the maximum and minimum distances?
MQ-3 Alcohol Sensor is base the amount ethanol molecules that is present near the electrodes. Therefore minimum and maximum distance had no or little bearing.
To give a little insight in to how the MQ3 sensor works.
The sensing element as shown in the picture below is a cuboid structure made out of an Alumina (Yellow) tube covered with Tin Dioxide (Light Brown). The electrode which is made out of Aurum is shown in Black.
The pin out and a drive circuit for the sensor are shown below.
The above circuit activate the heating element.
As a result electrons begin to move because Tin Oxide ceramics has become a semi-conductor.
Now when air with alcohol elements enter the cuboid structure the circuit generate additional current because the ethanol burns into Acetic acid.
Therefore the minimum or maximum distance has no bearing, but the presence of alcohol will have significant effect on the sensor. For more detail information review the references.