Here I am posting the schematic of the current design, and my proposed schematic for design revision 2. The main changes are:
- Directly drive the ROW inputs with transistors, instead of using shift register. I have enough I/O pins that there is no need for a shift register here, and the transistors will allow a decent amount of current through.
- Limit the current coming out of the COLUMNS with resistors. This is needed now that there will be more current flowing through. Before I got away without them, probably because each row was being driven by a single output pin of the shift registers
- Use shift registers on columns as before, but this time with a latch, so you wont see the data being shifted in. Thus the ‘off’ LEDs will really be off, instead of the faint flicker/glow
Schematic Rev. 1
(What I currently have built)
Schematic Rev. 2
(What I am planning to change next time)