[sdiy] Strobe Tuner Project

[James Patchell]

http://www.oldcrows.net/~patchell/StrobeTuner/StrobeTunerWebpage.html

That was all I managed to do this weekend.  I need to add a microprocessor 
(ATMega8515) to provide an interface to the user and to control things.

Here is a quick rundown of what it is supposed to do.

Mind you, there may be a few boo-boos in there...I think I have the gain in 
the AGC loop backwards, for instance...

The microphone goes into the the preamp.  The AGC is intended to keep the 
output at a more or less constant amplitude.  The output of the preamp gets 
converted into a current that is going to be used to drive the LED display.

The phase accumulator provides the reference frequency.  The upper 5 bits 
go to a decoder that will select one of 32 LEDs to activate.  So, if you 
set the phase accumulator to put out 440 Hz (concert A), the circle of 32 
LEDs will be "rotated" 440 times per second.  If the signal going into the 
preamp just happens to be 440 hz, you will see a pattern of leds being on 
in one part of the circle.  If the input frequency just happens to be 441 
Hz, you will see the lighted pattern rotate around the circle one time 
every second....actually, just saying this, I see one change I need to 
make.  I need to put a full wave rectifier between the current driver and 
the output of the preamp, that will give me an on pattern 180 degrees apart 
on the circle...

Anyway, didn't quite get it done enough to start a PC board :-)....maybe 
next week.



         -Jim
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http://www.oldcrows.net/~patchell

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