Just a quick question : I'm planning to build a LED Matrix, which will be over a table, with a satinated glass pannel over it. This glass pannel will hide the leds when they're not used, so that it looks like a "standard" table usually.
But I need to use bright leds in order for their light to get through this glass pannel. I made a test with WS2812B pannels, and they work quite fine. Their light gets through the glass pannel in a quite perfect way. Nevertheless, they require 15A for a 16x16 pannel of leds at full white, so 60A for a 32x32, which causes quite some powering issues - although we've been able to find solutions for them.
But I've also found this 32x32 adafruit LED Pannel, but I do not know how bright they are - but they only require 4A for a full white matrix. Would someone know how they compare ? Are they just as bright ? If so, would you know how that is possible, as both use just 5V ?
Thanks for your help If you're interested for some reason, we've also discussed this project here.
Keep in mind that these displays are designed to be driven by FPGAs or other high speed processors: they do not have built in PWM control of any kind. Instead, you're supposed to redraw the screen over and over to 'manually' PWM the whole thing. On a 16 MHz arduino, we managed to squeeze 12-bit color (4096 colors) with 40% CPU usage but this display would really shine if driven by any FPGA, CPLD, Propeller, XMOS or other high speed multi-core controller. The good news is that the display is pre-white balanced with nice uniformity so if you turn on all the LEDs it's not a particularly tinted white.
@Grumpy_Mike thanks for decrypting the message on their page, that wasn't quite clear to me ^^
@Paul__B indeed, it uses a quarter of the power, which strongly suggests a less bright display. But they use multiplexing, which is quite a smart trick and could lead to save some power while maintaining the brightness ?
Why would you say I'd be in a lot of pain with that display ?
But they use multiplexing, which is quite a smart trick and could lead to save some power while maintaining the brightness ?
No you can’t have your cake and eat it. Multiplexing reduces the average which results in a corresponding reduction in brightness. It is not a linear relationship because while the brightness is determined by the current, the perceived brightness goes up with a log law because that is how the eye works.
However an LEDs turned on and off an equal length of time quickly enough for it to look like it is constant on will look as bright as and LED on all the time with only half the current*
not quite but it is as close as makes no odds.
Why would you say I'd be in a lot of pain with that display ?
Because you have to keep refreshing the display and that will take up most of your processing power.
If you're interested for some reason, we've also discussed this project here.