BPM counter update: audio processing(not good)

Finally had enough time to sit and experiment with a bunch of different designs to boost and smooth the signal from an audio source. The few that I have tried didn’t work very well, the op-amp(741) with a LP filter didn’t boost the audio as much as i liked, it was giving poor results or no results at times, and  it used more components then i would have liked, since i don’t need audio quality sound, I didn’t feel the need to buy a dedicated audio amp or ICs. the other circuit i had tried was a LP  filter with a few extra caps, it looks like it would have worked but the audio signal was way too small to get a good reading.

So i scratched everything and started again trying to go for simple, So i decided to use a Transistor amp, or class B amplifier since i am only using half of the wave…

after the first few attempts it worked, not as i wanted but it did amplify the music, but it was not giving me the correct reading, when it was read it was giving very high odd values, between 400 and 900, and when plotted it did have a sine wave to the graph. the bad thing was it was a very small change in values and was unusable to create an algorithm to determine the beat, so i went to the drawing board, and looked at my design ,

I had figured i forgot the pull down resistor on the ADC of the arduino(oops), after that i hooked it back up and tried again…….now the weird part, it didn’t work……so i double checked everything, connectivity the transistor, arduino, and i couldn’t find anything wrong…it should have been working……so i have put it down for now till i figure out why its not working ………

I finally figured it out…..I killed my MP3 player that i was using as my source audio,  and now i have to find a replacement audio source that’s a little bit more robust then the one i just fried. an idea for replacement is use a 555 timer and set it at 120BPM and use that as my test source, but its just an idea……ill let you know how it turns out this weekend….

BTW if anyone has any ideas for a simple schematic program, it would help greatly,

everything i find has extra functions or some weird way to connect the wiring …..all i need is something that i can just place a symbol down rotate if needed and connect the wires….like using paintbrushes in gimp, then drawing a line between them……i tried that method too but no luck on the paintbrushes 🙁

if i ever get something simple or i find a parallel cable for my scanner, i will post all my test diagrams and schematics.