I'm looking for schematics of some simple opamp-based analog filter, which has a sharp band-pass functionality. I want it to control small robot with sounds of different pitch.
The matter is like this - to amuse my pupils I already made a robot which is controlled by digital filters. Perhaps this short demo explains better. However some of them asked if they can build similar thing.
My design is rather simple, but makes usage of a small MCU and about hundred lines of code. They complain they are not advanced enough in programming so I'm thinking of proposing "more analog" solution to them.
That is why I'm looking for substituting digital filter (and MCU at all) with analog schematics. I do know how to build first-order low-pass and high-pass with RC chain. And I can use several of them with opamps...
But filtering of 20 or 40 dB per decade seems to be not too sharp for my goal. The main problem is that controlling pitches should not be too far (e.g. I do not want to use 261 and 440 Hz) to ensure that sounds have roughly equal loudness. With simple plastic recorder tones of 784, 880 and 988 are ones of most easily produced and quite loud (indoors) - that is why I used them.
So now I'm looking for schematic consisting of preferably opamps, resistors and capacitors (preferably no coils) which will allow to extract very narrow band. Currently it gives about 0.3-0.4 of amplitude on, say, 784 or 988 Hz filter output when 880 Hz tone is played (and amplitude on 880 Hz filter is about 1.0).
Probably I just do not know proper keywords for googling. What such kind of filter could be called?
Thanks in advance for any suggestions!