Hi,

Well, my youngest just bought himself a bass guitar.  Anyway, along with
the amp we're building I thought I'd toss in a tuning indicator.  Found a
nice example of one done with an Atmel part, code in C, so I'm most of the
way there.  The only gotcha seems to be the PIC listening to the bass
pickups.  Input is via a series .02uF cap to the base of a 2N2222a, 330K
resistor to Vcc, 56K resistor to ground, PIC input is from the collector
with a 4.7K pullup, emitter to ground.  It does what it's supposed to
(amplify).  I get a nice pulse to ground at the primary frequency of the
string...  but I'm also getting what looks like some harmonics (or maybe
just noise) that are apparently getting amped enough to trigger the PIC
input (Schmitt trigger, A0 on a 12CE674).  Result is that the PIC almost
always says the string freq. is too high, even when it's ridiculously low.
Tried a few different resistor values on the base of the transistor, but
no improvement.

Well, blast it, I just broke a string playing with it...  Obviously
there's a better way to handle picking up the base frequency of the
string...  anyone got a bright idea that doesn't involve op amps and a
hundred components?

Dale
(yes, I **KNOW** I can buy a tuner for $12.  So?)
--
"Curiosity is the very basis of education and if you tell me that
curiosity killed the cat, I say only the cat died nobly."
          - Arnold Edinborough

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