I have just completed the 8x8 Matrix project from the EarthshineElectronics guide. It uses 2x 74HC595's to drive a 8x8 matrix, 1 row at a time. I'm using a USB powered UNO.
It works fine, except the rows that have 5 LED's on, will appear dimmer than a row that has 1 LED on - I'm not surprised in a way, but what is the solution to this?
The pinout for the matrix wasn't very clear, I have 270R on each (what I believe is) common cathode. Should I just reduce the resistor and will the difference in brightness be reduced/less noticeable? - surely the underlying issue would still exist? Is this a limitation of using the 595 and would this be solved by using a different (LED Driver) chip?
I am interested in the principle of this, to complete the project and my understanding - but also with a view to building an LED cube in the future, because surely that would suffer the same issue?
If someone could point me in the right direction, I would be happy to read up further myself.