I'm looking for a simple circuit that would sense the amount of airflow going through my air conditioning filter to give me an indication when the filter needs to be changed. I'd like to see the display telling me this rather than have to open the door up each time I want to know if the filter is dirty. I want the display to be an up/down LED bar display on the outside of the air filter while the sensor circuit would be in the back of the filter. Does anyone know if this is available anywhere for a modest price? If I have to make one up it would have to be a simple circuit. I was thinking of hanging a piece of cardboard behind the filter which, would be attached to a potentiometer. when the air moves the cardboard the pot would increase or decrease the voltage, acting as an air flow sensor. Can anyone give me any ideas about this. Thanks
Rod
Rod