Three months working on a commercial led matrix MMD project.
I'm using a 28 pin PIC18F2620 and 2x12
8x8 led matrices.
It's far from ready, even to a DS1307 clock drivers ...
But, to test and debug my main scrolling routines, I made
a simplified ISIS simulation and it's working fine yet.
It presents and describes almost all possible functions.
horizontal - vertical
left - right
scroll big (double)
settable CLOCK max 623
chars/message (limited by the PIC's RAM) max 90 fix
and one user modifiable message
insert a running clock into a fix message
Measured in ISIS the program is fast enough, at 16 MHz PIC clock
the whole refresh rate is better than 240 Hz
. In ISIS I'm using
a slower (4 Mhz) clock, so the refresh rate is better than 60 Hz.
I do not intend to make public the project, you must this understand.
But for those who are interested I uploaded a video which shows the
operation of the simulation: http://ifile.it/m0c2rwd/MyAvi.rar
Sorry for the quality of the video. It's caused by the asynchronity
of the two frame rates (speeds): the Proteus and the video capture.
And now here is my problem:
- how much average current should be for a good LED brightness,
(in my case 16 rows are multiplexed, all with 96 cols)
- if the led lits as well while its average current is 10 mA:
at worst case the max necessary current is 16 x 10 = 160 mA
on column side (I'm using 96 x BS170 Mosfet drivers here)
but all rows eat (at worst case) 96 x 160 mA = 15.36 A
(I'm using 16 pieces TIP147 pnp darlington transistors here)
Seems the peak currents are horrible ...
I think the column scanning is not better, well, only
16 leds lit at a time but multiplexed by 96 !
Is there a 8x8 led matrix wich lits well with 5 mA or less?
Please help me!