I have mastered a 8x8 LED matrix using two shift registers, and now i want to add another dimension to it. I have thought long and hard about it and have done a fair amount of research. I plan to make a 64x8 array. The illustration below I made a while ago, but helps understand what im thinking.
This design will use 9 shift registers, 8 to make the 64 columns, and 1 to make the 8 rows. This is based off the advice given to me from someone else who had successfully used this design.
However, it's not the design that puzzles me, but how i mange the current to stay within the limits of the ICs and the LEDs. I don't understand what i have to put between the shift registers and LEDs. I understand the need for 220-ohm resistors, but i have read in some places i need transistors to take the large load of the ICs when dealing with matrices the size of mine. I have seen a few different ways, from simply having lots of transistors to a 'Darlington Transistor Arrays' or LED Drivers. Futhermore, Hypnocube, a commercial 4x4x4 tri-colour cube, clearly doesnt have a resistor on every LED, which i thought was a requirement.
I have found no definitive answer for what i place between the Shift Registers and the matrix, and with my lack of experience, i have just got confused. Does anyone know how i should manage the currents as to not blow the ICs or LEDs? (And idealy, save me the need to solder 64 transitors and/or resistors, as done in the Hypnocube)
can you maybe share your code for using the 8x8 matrix with shift registers?
i heard you have to refresh the matrix or something like that, but i dont get it, and i have a 5x7 matrix, so im way too confused, so can you maybe help me since you mastered the 8x8?
oh yea, and if you go on the make website, one of the weekend projects is making an led matrix that was 9x9x9 i believe, go check it out, i'm sure thats what ur lookin for
That one has 16 bits, a search on google may turn up an 8 nit one at a lower price
Yes mem, i have seen the 16 bit LED Drivers, i was looking at the STP16C596, but that Texas Instruments one looks much the same. (I have even seen 32 bit ones) Are you saying that with 4 of thoes drivers, and a standard shift register on the other end, it will work no problem? That would be great, but from what i have seen is that shift register at the end cant handle potentially the current of 64 lit LEDs.
Offtopic: big93, about the LED Matrix. I am at work, but later on sure i can send my source. The basic idea is you start at row 1, and light all the columns you want lit on row 1, while sinking the row 1 pin, so only the first row is lit. Then do the same for row 2, 3, 4 and all the way to 7, and then do it all again. If you do it fast enough, using an effect called persistence of vision, your eyes will see it as them all lit up. (kind of how a CRT works) So just light a row at a time, really fast, and it will look like every LED is individually addressed.
A very good tutorial on the fundamentals of LED matrices is: http://www.nuxie1.com/guides/led-matrix-information.html (no code)
This blog post shows how someone built a Arduino based matrix: bryanchung.net - This website is for sale! - bryanchung Resources and Information. Edit: http://dotmatrixdesign.tumblr.com/ - Thats exactly what you want. 7x5 scroller.
