Help me design an air flow detector

[kiddly2]

i m doing my project about the air flow detector, but i have no idea about design this circuit. anyone can guide me ??

i just need to get HIGH output when there is an air flow detected, and LOW when no air flow detected

 

[ehsanelahimirza]

air low flow detector

hi

i can give u idea

u can use a fan type thing which is connected with a small dynmo of cycle,( it will produce AC voltage ) so u have to convert it or u have to use a DC dynmo.

when air is flowing dynmo will produce current by the motion of fan

 

[pqtam]

application and working air flow detector

i m doing my project about the air flow detector, but i have no idea about design this circuit. anyone can guide me ??

i just need to get HIGH output when there is an air flow detected, and LOW when no air flow detected

Hi, what sensitivity u want? flow of 0.1 mm/h speed or 100km/s?
If speed is enough, use flag mechanism to toggle microswitch.
If hi sensitivity required, use 2 diaphragm, one can be waved (like door mechanism), put across the flow direction to detect flow, the second (smaller) is tighted with the first with 90 degree and used to block IR (or other light) passage of the optocouple. When flow comes, the 1st diafragm will be waved, carrying the 2nd to close the light passage, which lead to HI (or LOW, whatever you want) signal from light receiver. Sensitivity depends on the area of the 1st diaphragm and resistance of the waving mechanism.
pqtam

 

[VVV]

optical clogged filter detector

There is a way to detect it electronically, the so-called "hot-wire" method.

Basically you have a resistor bridge, where sufficient current passes through it that the resistors heat up. Only one of the resistors is exposed to the airflow. Because of the airflow, this resistor cools down, its resistance becomes different from that of the non-exposes ones and the bridge goes out of balance. You can then detect that condition and signal a lack of airflow.

(Incidentally, this is the method used in many modern cars to measure the engine intake air mass. MAS stands for Mass Airflow Sensor, because the resistance of the wire changes with respect to the MASS of the air flowing past it. But you can use it for your project).

Obviously, if you are going to build your own resistors, choose a material with a large coefficient, so you get good sensitivity.

 

[Siniša]

working of air flow detetor

Detection of air movement can be obviously done in number of ways but most common are paddle that activates switch or interrupts light beam or thermal method mentioned earlier. Thermal method is used for low air flow mostly as safety for active cooling systems. You could use brushed DC fan as generator for higher air flows.There is also measurement of pressure differential measured at ends of tube used mostly to detect clogged filter in projects that are not cost sensitive. If you require sensor for project and do not need to reinvent wheel, there are number of sensors out there made for that purpose. For example Klixon,TI's subs. makes 2SE series air flow sensors on thermal principle.

 

[martin martinez]

micro switch used as flow detector

maybe you can try w a sort of a windmill tipe thing
adapted to size and flow of your needs and some small magnets and a hall effect(magnetic sensor)
like some tachometers do or something like the wheels inside the mouse they cut the optical path of a ir pair and send pulses every step!!