Looking for idea validation and hopefully to hear that I'm on the right track. I'm planning to build a coat that has embedded (common anode) rgb LED's. It will likely have around 50 or so.
I plan to power it externally through a couple ULN2803 darlington arrays to sink the rows (more about this in a second). To power the pwm, I'm daisy chaining multiple TLC5903 shift registers.
The idea is to have the LEDs under the material basically go through the color crossfade tutorial (here). I want one led to start randomly, while multiple others are still going. Trying to do this in a standard loop with multiplexing seems impossible given the memory constraints, but please correct me if I'm wrong. So I figured I would strobe through the rows with the darlington array, while the pwms pins drove a column at a time and make use of POV. Is this reasonable given the refresh rates?
My backup is to use 50 apa102 "smart" pixels and try and drive them somehow from external power, anyone have experience with them? Id rather spend the extra money on pixels instead of having to fab a pcb for the controller.
Why do you talk of PWM and multiplexing in the same breath.
You can not do them as the same time because it is impossible to sync the two processes.
I'm not sure if I am misunderstanding you, or you are misunderstanding me. My plan is to use the TLC5940 to pwm control chains of rgb leds. Then use the ULN2803 to turn off rows that dont need to be on. For example below, column "1" would be driven by pin 1 from the TLC5940 (really three pins since its rgb), and rows a,b,d, and e would be turned off in the darlington array, thereby lighting up [1,c] with full PWM control. How is that impossible?
1234567
a xxxxxxx
b xxxxxxx
c xxxxxxx
d xxxxxxx
e xxxxxxx
My plan is to use the TLC5940 to pwm control chains of rgb leds.
You never said anything about using a TLC5940 in your original post did you?
You said:-
To power the pwm, I'm daisy chaining multiple TLC5903 shift registers.
http://www.ti.com/product/tlc5903
Yes, I mistyped the old model number for another LED driver that offers pwm. How exactly would that make your original comment relevant or pertinent at all?
I'm new here, so I'll just go out on a limb and guess you're the guy that berates all posts and is generally unhelpful, while maintaining an air of superiority. Every forum has one.
Anyone like to actually help?
Look at the Karma points, you don't get to be that high without helping someone.
Chips have all sorts of numbers and the description of the chip and the number you gave is not enough information for anyone to know you made a misspelling.
Awaiting apology.