Hi,
For a project I am trying to implement the circuit in the attached file "circuit". The two 6V supplies are 4AA packs.
It's a differential amplifier whose input is coming from a piezo disc that is acting as an audio receiver. The peaks of the signal is then counted by the Pro Trinket to determine the frequency.
This circuit and the code was verified on an Arduino Uno that was plugged into a laptop. When transferred onto the Trinket (battery powered) we no longer got the results we wanted.
This is the 5V 16Mhz Pro Trinket
My thoughts:
It seems the virtual ground is the problem. We have an arduino uno plugged into a laptop and if i short it's ground the the virtual gnd then everything works great. You can see the input signal from the piezo going into the Trinket in the attached file "with laptop gnd", where the top cursor is at 1.9V, the minimum voltage level for a logic high on the board.
With only the virtual gnd we see what is displayed in the attached file "no laptop gnd" where again the top cursor is the 1.9V threshold for a logic high. We're obviously not crossing that in this scenario at least most of the time.
I've tried switching the Trinket gnd from the virtual gnd to Vcc- for a "true 0V gnd" but no help. Also tried powering the arduino with a separate 12V (8xAA) battery pack which also did not help. As well as connecting the virual gnd to a piece of metal in hopes of a chassis gnd.
Not too sure what else to try here.
Thanks in advance for any input!
