air flow sensing

Hello:

I found this circuit on the web. By its description it seems sensitive enough for an air sensing circuit for an electronic musical instrument I am building. I can make it work by blowing a strong current of air, still how can I make it more sensitive?

Thanks in advance for your help.

The gain of the circuit is proportional to the ratio of the feedback resistance to the input resistance = Rf/Rin. For you, Rf = 100k and Rin = 1k + C1's reactance. You can put a 500k trimmer pot in series with Rf and have variable gain. An LM324 may not have the horsepower you need to get a lot more gain.
The little SCR circuit "A" could cause you bodily harm if it is tied to the AC mains as mentioned in the blurb.

Try replacing R2 for a 1 meg ohm, that'll give you 10x more sensitvity.

You could use another one of the 4 op amps within the lm324 to give another gain stage, you just need another couple of resistors and a capacitor, only I cant post a drawing, try the 1 meg first.

The little SCR circuit "A" could cause you bodily harm if it is tied to the AC mains as mentioned in the blurb.

Click to expand...

Also, if the load is an AC motor or transformer you could fry it, as the SCR passes DC, not AC.

Have you looked at differential pressure sensors?

You could replace the scr with a triac for AC loads.