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Help Needed:3 kHz Bandpass Filter Design

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audioguru

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Your bandpass filter is fine except:
1) It must be fed from a very low impedance like the output of an opamp.
2) It has a high gain so its input level must be low.
3) C1 should be about 10uF so the bottom end of R4 is grounded at 3kHz.

Your schematic does not show the supply voltage.
The scope does not show which trace is which.
If your input is 6V p-p then it is way too high.
 

audioguru

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Most Helpful Member
It is too bad that you posted your schematic over at Image Shack instead of attaching it here. It takes Image Shack half the day to wake up and their popup ad is a nuisance.

Where is your other thread about measuring the distance of a gunshot?

Another problem with using a bandpass filter for a gunshot is that it takes time for the signal in a bandpass filter to build up. The sound will be gone before the filter 's output reaches the correct level. Echoes will add to the level.
 

gurunz

New Member
i try to attached it but cant and i only know imageshack to host my image.
My other post at edaboard forum.i think i succeed to design bandpass after testing it yesterday evening at lab but...ughhh...another problem...thankfully u mention it here about time opamp needed to build up signal....another problem to solve...i have samples of m16 gunshots, all the gunshot sample duration is 2 seconds.Do you think it is enough time to op amp build signal? thanks again audioguru for helping me alot
 

audioguru

Well-Known Member
Most Helpful Member
Compare an unfiltered sample of the sound of a gunshot with the bandpass filtered signal and you will see on an oscilloscope that the duration of the BANG sound from the gun is too short for the bandpass filter to accurately show its amplitude.
 
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