I mentioned this in a previous section here but I wanted to acknowledge that whatever I learn for my own project I gained MORE useful information from this thread http://arduino.cc/forum/index.php/topic,114901.0.html than from all of the video I have researched and watched on YouTube. So kudos to Pedro for sharing his process and Crossroads for his considerable level of help. Obviously, there were others in there so don't think I left you out
When I saw that site above I knew I wanted to recreate it. I know I could buy it but where is the fun in that.
Believe it or not that window decoration is a 8x8 LED setup and I believe they are using Super Bright LEDs. Most of the animations are 20 frames in length so it is VERY doable with Arduino.
I am almost at the build stage for the 8x8 but I am waiting for my shipment of components including a 74HC165 and a 74HC595. I ordered both not knowing which one would be best but I am sure that will be an easy task.
While my parts are shipping I will ask this of anyone. I know there is some fabric that might be good for mounting of the 8x8 LEDs but as far as I saw it was pretty much a small size. At the commercial site they are using a plastic backing for the LEDs but I know zero about how that could be created...maybe it is an outsourced kind of thing.
For now...I will mount on some kind of stiff cheap board unless someone has an idea. I am completely open here.
Now for a design question.
What is the Darlington ULN2803 component used for in Pedro's project? In some other LED matrix designs that I have studied it does not appear.
Yes, I will be posting pictures and code as I progress so stay tuned until I get my parts. lol
In Pedro's thread, reply #15, the ULN2803 sinks the current from all the cathodes.
If all 8 LEDs in a column were, that would be up to 160mA. A 74HC595 alone cannot do that. I think it has a limit of 70mA for the whole chip.
Another choice for the 2 chips would be to use a TPIC6B595, which is a shift register with high current sink capacity - so pretty much a combined HC595/ULN2803 in one package. But I think Pedro wrote that he had the '595s already.
Whether a high current buffer is used depends on the multiplexing scheme.
If you want to light a whole column at once, a buffer is needed.
If you want to parse out the anode bits one at a time, then you can get by without. Refresh rate is 1/8 or less of what you can achieve writing a byte a time.
I come from high speed hardware design world, no way I'm doing 1 bit a time.
Believe it or not that window decoration is a 8x8 LED setup and I believe they are using Super Bright LEDs. Most of the animations are 20 frames in length so it is VERY doable with Arduino.
Sounds like a job for the MAX7219/MAX7221. Simple to use with arduino library support. Low component count 1x MAX7219, 1x Resistor & 2x Capacitors per 64 LED's (Arduino Playground - HomePage) Chip can be cascaded. LedLibrary supports 8 chips so 512 LED's
As soon as I get my 74HC165 from the slow boat I will be starting (Arg! I hate the wait).
I don't have the other chips (MAX7219 or ULN2803) but I will order those as well just so I can see the differences between them and the effects they create.
I figure I don't need them since the example I saw on the Arduino.cc playground area did not have them. If I have to wait much longer I may do a raid at a local mom n pop electronic store.
DipMicro is who I am waiting on. I got the express shipping so it should be here any day...I hope.
After I put my order in with the Chinese it clicked with me that it might take a few months to get over here so I placed a quicker order with DipMicro.
I just need to be a bit more patient. The lack of it has been a curse for me. lol
Dipmicro stuff comes quick. I just got a box with power adapters, couple of LCDs, motor shield. Ordered the 21st, late at night of course, was here the 24th or 25th.
