Strange current occurance?
As a test I wanted to see what would happen if I lowered (1 of the 16) - 22 ohm resistors my matrix is using to a 2 ohm. Surprisingly I saw no difference in brightness. The brightness is lowered when 5 or more LEDs are on a column.
As another test, I removed the resistor and still saw no difference. I started removing all of the 16 current limiting resistors and so there were no resistors (just 16 anodes, 16 cathodes, 2 UDN2982s and 2 ULN2803s going to 32 I/O lines of the SX52.
What I did notice is that the current was measured previously at ~300 - 640 mA. Now it appears to be about 20-30 mA.
Does this sound right?
On a side note....I etched a custom soldering board with 16 of the surface mounted P-Channel 2.4A FETs as described earlier. I will take out the UDN2982 and try using this double sided PCB (8 P-FETs on each side) and see if this helps. This means there will be (as a test)...16 Anodes, 16 Cathodes {LED matrix 256 LEDs total}, ULN2803 (2) - {probably should add back the 16 - 22 ohm resistors - but this time put them on the outputs of the ULN2803s not the UDN2982s - that are replaced with the P-FETs}. Do I need to pull up 1 K resistors on the Gates of the P-FETs?
Thought...Comments.