breath control

Hello!

I want to convert someone blowing to a variable resistance/current as cheaply as possible...

I was thinking that I could use a cheap fan with a small magnet attached to it and a relay as the input (kind of like a bike computer works) and read that to a pic (ie how many times a sec the rlay is switched) , then output that to something that would control a variable resistor... does this sound like a good way to do it and anyone have any suggestions for components/code? I normally use a PIC16F876.

I live in the UK (london) and am a bit of a beginner at all this!

thanks very much for your help..

I would suggest something like how car Mass Air Flow sensors work.

You can use a flap in a tube that's attached to a pot. when air is blown through the tube, the flap is pushed aside and turns the pot. Obviously there's less air moving, so it would have to be more sensitive.

Also some use a heated resistive wire. They measure the cooling effect on the wire by the air that passes through the tube.

I would use a flow sensor. turbine type. it out puts a freq that represents the flow

use a thermistor with a resistor in series and a comparator sense the
change.