"tiny" single i2C or serial RGB led controller

[TucoRamirez]

btw, i have an offline question ...

it's concerning the following...

if i made a led pannel (10x10 , RGB)  , and i have to do some tests with a camera to check patterns and detect colours (on a translucid surface)  what will be the most efficient way to not perturb on any way the sensors :   simultaneous pwm signal on each led  or  multiplexed like zuisti's MMD  ?   

its my one penny question as long as i have not received the components yet ^^

[ehnonymouse]

  what will be the most efficient way to not perturb on any way the sensors

I'd like to help you with this, but I'm afraid I don't understand what you mean here. Is there any chance you could explain?

[Gallymimu]

I can only guess he is talking about flicker due to the frame rate of the camera?  Is that what you are asking?

[TucoRamirez]

yes off course, i mean, a cmos image sensor ( in a first state a webcam )  will watch to the led panne ( i'll put a translucid screen)   to test some colour , brightness and pattern profile detection algorithms...   but i'm affraid if i use a multiplexed matrix technique the sensor will have troubles identifying the whole pattern at a specific analyse instant  (or instant picture of the pannel)

thanks for your interest, 

[SpaleKG]

If you use camera (ie. slowest web camera with 10fps) then you need to have vertical scan at least 50-100Hz in your muxed matrix. For better cameras like 20-25fps that should be x10 about vertical scan (200-250Hz) of your LED panel.

[TucoRamirez]

and in the case of a picture taken of it???   (i'll confirm the strategie of the 'robotic eye' testing the pannel in 2 weeks when the chief of the project will be back from hole-in-days )

thanks again, at least i'll do a parallel pwm with a tiny pic just for initial test then i'll switch to a usb F2550 maybe to use its more ports and pins ... still in paper and pen mode until final response about the flicker stuff

[Gallymimu]

If your LED power is low enough you could put some capacitors on them to stabilize the output and reduce flicker.

[SpaleKG]

and in the case of a picture taken of it???   (i'll confirm the strategie of the 'robotic eye' testing the pannel in 2 weeks when the chief of the project will be back from hole-in-days )

thanks again, at least i'll do a parallel pwm with a tiny pic just for initial test then i'll switch to a usb F2550 maybe to use its more ports and pins ... still in paper and pen mode until final response about the flicker stuff

The single shot picture is one frame. Speed of that frame (how long camera will store all pixels) is as long as one frame in 25fps. So if your camera does 25fps then your single shot will be 1/25 of second. So it is same as for moving pictures and do the math. Also some cameras (like camera in iPhone) have delaying until picture is stable (no movement). Those type of cameras avoiding flickering.

[Ichan]

ok i found a solution ...  200 hz output and > 64 PWM outputs with shift registers and the pic12f1840   controlled by RS232  ...  i tested on simulator now i'll buy the ci to real test

I would like to see the schematic and code, it must be interesting - so you will generate 64 channel pwm using serial in parallel out shift register, it must be a tricky one.

-ichan