I’m designing a 64x32 panel with yellow LED’s. This is a high brightness panel with a 1:8 multiplexing ratio. Dimming is also needed. To dim it I’m using a TPS54331 with a bit of voltage adjustment circuitry added. I’m using one for each 8 rows. With a 12Ohm current limiting resistor it allows for the max 150mA pulse per LED or 50mA max continues current per LED. The panel input itself is 10-18V. Controlling this is something i have to add myself as far as i can tell but should have enough pins available.
Currently I have one data line for the columns of each 64x8 sub cluster. Address lines for the active row are shared. I guess this gives me 4 parallel rows in reality. Seems like I can run it as 2 panels each with 2 sets of shift registers.
The total panel will consist of 3 64x32 panels in a row to make a scrolling text sign.
Do you have to design your yellow panel, or can you use strings of neopixels that can easily be made a matrix out of, even if they will cost you around $400 fo 64x32? (but it’ll be pre-made, on need to re-invent the wheel and depending on your deployment size vs your engineering time, may be worth it?)
I looked into a neopixel based solution. At 4-5 cents an LED it would be quite cheap. The relative inefficiency would be fine. Only problem is the wide angle light output and lack of light output. The current LED’s have a light output of 3000mcd while the WS2812 based led’s only have 500 ish. The bad representation of yellow is also an issue. The 3000mcd is also at 50mA while the LED’s can take up to 150mA for short pulses
neopixels are on 100% of the time. RGB panel LEDs are on 1/4, 1/8th, or even 1/32th of the time, so you have to divide the light output by 4 or even 32. neopixels will always be brighter in a matrix in my experience compared to RGB panel LEDs due to the row scan issue (unless you get some new PWM panels with built in refresh, but they are not supported by this lib)
