Greetings! This is an acoustic drum lighting board (driven by piezos on the drums, run back over CAT5 to the PCB for processing) that drives 8 separate strands of 12v RGB LED strips over CAT5 cabling with a simple breakout module on the other end to break it out from CAT5 to the appropriate contacts on the LED strip. The Arduino is handling this via 3 chained 74HC595 shift registers (with .1uF decoupling capacitors on each) and an Arduino Nano 3 (since it has 8 analog inputs).
I etched and drilled the PCB, made sure to check all traces for continuity/shorts (no errors) and am assembling the board one channel at a time to make debug tracking simpler... Each "channel" consists of 3 Tip122 transistors and 3 220ohm resistors coming off pins from the shift registers. Upon completing the first channel, all 3 components of the RGB LEDs worked fine on a test strip over 6ft of CAT5. --- After installing the 2nd channel (still leaving 2 pins not connected on the only shift register currently installed), now the transistor controlling green on the first channel does not work (but blue and red do) and the transistor controlling red on the 2nd channel stays on statically (blue and green work as expected). I thought it may be a cable or trace issue on either end, but if I short the red or blue pin on the outgoing RJ45 port to the green pin, it works as one would expect by lighting in accordance with the shorted pin.
As a note, I am using the ShiftPWM library with a debug/test function running on the arduino that simply turns all outputs on and off in 1 second intervals, nothing more. Thank you in advance to anyone that can offer any suggestions as to what may be causing this bizarre effect, for I am on a time crunch that requires this board to be working within several days.
