Hello
I'm building a big 16x12 led matrix using 5mm UV LEDS. considering the amount of rows to toggle, are resistors going to be necessary?
I'm guessing they will be flashing too quickly to burn out..
Thanks for your advice
However your circuit is designed it is required that you don't draw more then the recommended current from any digital output pin, say 30ma or less and that the total current drawn from all output pins is lower then 200 ma. This can be accomplished several ways such as constant current driver components or simple resistors. Either way the design has to ensure that the processors electrical specifications are met. Using external drive components can be one way to increase the current capacity for driving large LED arrays so as to not let the processor be the limiting factor.
Lefty
Hi Richard, retrolefty,
Sorry about the disclosures, I plan to use 4 595 shift registers to power the matrix, feeding off a 12v 1A wall wart.
The project is a monophonic sequencer (12 note, 16 step) so I only intend to light one LED on each row (one led at a time).
Thanks for the insight and pointing me to the Led Resistor Calculator, this will be very useful.
Thanks!
Then you said you were using four, 8-bit shift registers = 32 channels.
32 channels can be arranged in a 16 x 16 matrix, which is good enough for 16x12.
Korman
You always always ALWAYS need some form of current limiting when you drive an LED. Normally this is a resistor but it can be a constant current regulator for higher powered stuff. See:-
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html
12 Rows of LEDs for notes + 16 columns of LEDs for steps = 28 channels needed for the matrix.
With four shift registers I'll have 32 channels available, 4 will be spare.
If I've understood the principle of a Matrix and considering that only one note will be lit per step/scan, I'm only looking at powering one LED at a time. I will use the appropriate limiting current though.
Just wanted to clarify
Best
Alex