Need suggestions for a project...

[no1unorightnow]

I decided to make one of those music/lights synchronized Christmas displays, but I need a bit more information; I need more digital I/O pins than the most of the boards have. The Arduino Mega would have enough, but it has lots of analog I/O pins, too - thus adding cost for features I wouldn't use.

I have my computer playing the music, and sending the commands to the board to turn lights on/off. I tried other ways, such as having the board initiate with the computer, and then continue on its own. However, the way I have it now is my preferred way.

The best option that I can think of is if there were some way to turn analog pins into digital pins. Other ideas so far include:

Use more than one board attached to the computer (ruled out because of changes in code, multiple USB cables, et cetera)
Use one board connected to the computer, and more boards attached to it (haven't tried yet; might be the best option)
Use one board connected to the computer, and then use one of these things (not sure how this works... Delays? Individual control of a light going on/off?)


Main concern: latency and/or delays. I want the time between the following two events to be as little as possible:
1. Computer starts sending command to board.
2. Light has finished changing its state, and the board is ready to receive another command.

Once I decide on my physical interface, I plan on adding transistors (and, if necessary, resistors,) to the "controlled" electrical contacts, so that I can drive 12V LED strips.

Also, if anyone knows of any LED strips specifically approved for outdoor use - preferably "winter-resistant" - that use 12V power, that would be awesome, but I have a plan either way, provided I can get the physical control interface taken care of.

[floresta]

if there were some way to turn analog pins into digital pins

Pins A0 - A5 can also be used for digital I/O as D14 - D19.

Don

[oz]

I'm not dead certain on what you are trying to do, but I think the 8x8 board could work well for your display. The driver chips on the 8x8 are open collector - so you can drive the LED's up to 17V @ 90 mA on each pin. This would require NOT using the positive line on the board and powering the board with a separate 5V supply - then tie all the positive 12V (or whatever other voltage up to 17) lines together at the supply. No transistors necessary - no fuss, no muss. Well, maybe LESS fuss, it's still lots of wiring hooking it all up.

Paul

[no1unorightnow]

Cool, I didn't know that about the Analog pins... Thanks!

I don't know the specs for those lights I'm planning on, but either way, it sounds like the 8x8 LED board should work... I just ordered one last night, so I'll be testing some stuff soon.
Also, weatherproofing the Arduino/8x8LED shouldn't be necessary, if I have those inside the house, and just run the wires out to the lights. Thanks again!

[bperrybap]

How many LEDs are you trying to control?
You can control up to 120 on a m168/m328p and still use the 2 pins for serial communication.
The trick is to think multiplexed where not all of them are lit at the same time and
to use a column and row addressing scheme.
To get to 120 you have to cheat a bit and reverse the voltage so that there are actually
2 LEDs per column/row combination.

See this neat little project for an example of what you can do with that many LEDs.

http://www.nerdkits.com/videos/ledarray2


For LEDs, check out superbrightleds.com , They have all kinds of stuff:
Here are some flexible bars:
http://www.superbrightleds.com/light_bars-flexible.html

--- bill

[no1unorightnow]

Thanks for the info, bperrybap. I think I'll stick with the 8x8 for the light setup, but I do plan on trying stuff from SuperBrightLEDs.

Also, the package arrived yesterday, but I haven't put it together yet. I need to look into the "trace cutting" thing...