What components are actually driving the LEDs?
The modules are wired in a matrix format: there are 128 row lines on each side. Along the bottom, driving the columns are 384 column lines (each column has two lines: one line for red and another for green). The row lines are driven by TIP125 Darlington power transistors. The sign has a total of 256 power transistors. Row-wise the display is split in half. Each row has a drive transistor for the left half and a drive transistor for the right half. I did this because had only a single transistor been used per row than that transistor could potentially have to drive 384 LEDs at once. Although the TIP125 is rated to 8 Amps, current division and IR losses would cause the side opposite the drive transistor to be significantly less bright than the side nearest the transistor. Also, to further lessen the effects of IR drops along the power rails (which are 16 gauge Monster cable) the left side and right sides are never driven at once: the left side is enabled while the pixels for the right ar
