I'm very new to electronics and Arduino. I'd like to build a prototype of a custom LED display that needs to control, in a fixed pattern, a min of 256 LED's, preferably 512 or even 1024! ! It will have quite a few individually addressable groups of 4 different colored LED's that need to flash 1, 2, 3, 4 then repeat. It needs to be able to cycle thru the pattern at a variable rate from 1 fps to 30 fps or 100fps, the faster the better! Note that at any given time only 1/4 of all the LED's are on.
So can an Arduino microcontroller and its other hardware, in addition to whatever other components I'd need to buy, handle such a task? Or would a Raspberry Pi be better suited?
Which model would be best for my needs?
Thank you for the advice.
I would go with the WS2812B like CrossRoads said.
However the problem might be memory, you need to store three bytes for every LED so if you have 1024 LEDs you need a buffer of 3072 bytes. For a Uno you only have 2048 bytes of memory in total. That means you would have to go for a Mega which has 8K of memory.
Or would a Raspberry Pi be better suited?
You can drive the WS2812B from that, there are two projects in the MagPi issue 36, free on line from:- The MagPi issue 36 — The MagPi magazine You don't have the memory issue but you need to boost the output signal from 3V3 to 5V. Note that the driver library currently does not work on the Model 2, fortunate you can still get the B+ version.
However, the power supply is an issue. At 60mA per pixel then 1024 LEDs work out at a current of just short of 62A and that is going to take some supplying and correct handling.
MyWebs:
It will have quite a few individually addressable groups of 4 different colored LED's that need to flash 1, 2, 3, 4 then repeat. It needs to be able to cycle thru the pattern at a variable rate from 1 fps to 30 fps or 100fps, the faster the better! Note that at any given time only 1/4 of all the LED's are on.
Do the colours of the individual LED's need to change or do they always stay the same colour? This will make a difference to what type of controller is best to use and what type of Arduino.
Atmega1284P would be good too, 16SKRAM (twice that of Mega) for more storage options.
I offer them as Uno-like boards and other form factors, couple examples: http://www.crossroadsfencing.com/BobuinoRev17/
First thank you everyone for your advice and related links.
I've tried to learn all I can in a short amount of time about LED's and basic electronics, I've even bought a radio shack electronics learning kit.
Let's say I'm making an 512 fixed color LED array, I would like to use 128 red, 128 blue, 128 green and 128 purple fixed color LED's. It would be divided up into groups of 4 with one of each color. I have learned that each color uses a different voltage so I'm afraid that constantly outputting 4 rapidly changing voltages might be difficult?
The only other alternative I think would be rgb LED's which, always?, use a pwm signal to achieve desired color. Here I'm afraid that a pwm signal would slow down how fast I can strobe the LED's thru the desired color pattern since the pwm signal is also constantly pulsing many times per second. In this case I'd only need 128 rgb LED's to be the equivalent of the 512 array since one rgb led can do all 4 colors. In this configuration all of the led are on at one time, just constantly changing between 4 colors.
I'm open to doing it either way. I figure it would probably come down to tradeoffs between costs, speed and design complexity. Eventually I'll probably experiment with both approaches to see what's best overall.
The WS281B look way cool and very functional and keeps the led cost down to around $50 or $100 if I can still very rapidly strobe them if they use pwm.
I have previously looked at ur products Crossroads and suspected they might do what I need but wasn't sure how many led they could controll or how fast?
I've also looked at 555 timer, shift array IC, fpga, led drivers, DMX controllers and much more. I just don't know enough yet to know which direction to proceed. I figured an Arduino might be a good place to start learning and moving forward with this idea.
I'm afraid that a pwm signal would slow down how fast I can strobe the LED's thru the desired color pattern since the pwm signal is also constantly pulsing many times per second.
No PWM is pulsing many times a second faster than you can see, and so will not limit you to the speed you can change patterns, because if you got anywhere close to changing the patterns as fast as PWM then you would not be able to see the patterns change, it would be all one blurred blob.
