First Tests

A project log for Clipper - A Clip on Tuner for Musical Instruments

Minimalist LED strobe style clip on instrument tuner using a SAM D11C and a piezo sensor with LED readout.

rrace001rrace001 08/23/2019 at 00:080 Comments

The different color LEDs have a drastic difference in brightness.  The photo is terrible because I turned off the flash for the LEDs to be visible but it does not show the brightness difference due to this.  The outer ring is made up of diffused white 0603s and the 7 segment is made up of clear blue 0603s.  The white is very bright and the blue is not so bright.  I like the diffused so the next iteration will have diffused all around and I will try to better match the LED brightness.   Overall the circuit is drawing to much current which was somewhat anticipated.  I have a couple ways to deal with this so I might be able to keep the 2032.  If not then either go with a AAA with a booster or a lipo.  The opamp works best when being powered by a battery but I want the AAA and that needs the booster.  Could go with two 2032 but not sure.  Hard decision...

The middle scope snapshot is the g string and it is clipping because there is only about a volt and a quarter head room do to the LM324 1.5 volt limit within the positive rail.  This is anticipated as the voltage divider is 1/4 VCC.  The clipping on the top and bottom is about even so that turned out good.  I zoomed in another step for the E string, bottom, and struck it a little lighter.   This has me worried because of the noise on top of it.  Could not get rid of it by striking the string different or muting the others.  Not sure if that is a harmonic or some type of ringing.  I left out the filter capacitors on the feedback paths of the opamp to save some room but now I am thinking I should not have done that.  I am going to try and piggy back the first feedback resistor with a cap to see if it reduces this noise - if that is what it is.   I have never seen that before so a little confused.  I might also try swapping out the LM324 with a LMV324 for the rail to rail and possible cleaner feedback.  My other projects never had it so I need to do some probing....