avoid the Matrix with this large number of LED's
Steel
Posts: 313
You may want to avoid the Matrix with this large number of LED's.
It will cut down dramatically on wires, but there is a HUGE drawback...
If you can only scan 1 row at a time, then the PWM of that row will be greatly reduced by the number of rows you have...
...If you have 10 rows of LED's, each row will only be illuminated for 10% of the time.· This will make your Display very weak, and appear to be flickering.
The best solution is to control each LED individually without running a matrix.
Post Edited By Moderator (Joshua Donelson (Parallax)) : 10/23/2009 4:33:08 AM GMT
It will cut down dramatically on wires, but there is a HUGE drawback...
If you can only scan 1 row at a time, then the PWM of that row will be greatly reduced by the number of rows you have...
...If you have 10 rows of LED's, each row will only be illuminated for 10% of the time.· This will make your Display very weak, and appear to be flickering.
The best solution is to control each LED individually without running a matrix.
Post Edited By Moderator (Joshua Donelson (Parallax)) : 10/23/2009 4:33:08 AM GMT
Comments
You are absolutely correct if one multiplexes in a straight sequential manner.
On the other hand, if only a few (say less than 5) LEDs out of the hunderds need to be illuminated at one time, then one can do some smarter form of mutiplexing.....don't bother with rows/columns that are not needed. So its a matter how many leds need to be on at one time. With "Charlieplexing" this relates to a brightness inverse of the number of "on" LEDs, so one compensates by hitting the LEDs harder during their "on" period.
And then of course the brightness can be dynamically altered by the mutilexing time ratios...
Cheers,
Peter (pjv)
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Chris Savage
Parallax Tech Support
csavage@parallax.com