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upsidedownlabs / DIY-Muscle-BioAmp-Shield

A Do It Yourself (DIY) Electromyography (EMG) shield for learning neauroscience with ease.
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BandPass filter poles do not match the description on schematic #4

Open kevinjwalters opened 9 months ago

kevinjwalters commented 9 months ago

The v0.3 schematic describes the active filter as a BandPass filter (72Hz - 720Hz).

If I calculate the poles of the filter I get 159.15 and 723.43, the lower value does not match, why is that? I found an online bode plotter http://sim.okawa-denshi.jp/en/optool.php and it agrees with the frequencies I calculate.

udl-muscle-bioamp-v0 3-bpfilter-values

udl-muscle-bioamp-v0 3-bpfilter-bodeplot

lorforlinux commented 4 months ago

Hey @kevinjwalters, we are using 2.2uF on the production board of Muscle BioAmp Shield. Thus you are seeing 72Hz-720Hz on the specifications. I will update the schematic to reflect this production change.