advice on long strands of rgb led strip LPD8806

[hcgilje]

First of all,
I am really happy with both the led strip itself and the excellent library for it.

I have a few questions related to upcoming projects which I think might be half-answered in other threads, but just to make sure I understand this right before ordering more:

In one project I will have 7 separate strands, with a total length of about 25 m. The longest one will be 5m, the shortest one about 2m, and they will be running different animations/patterns.
Would it be most efficient to connect them in series from one microcontroller?
How many strands can run in parallel from one arduino?
If I understood the discussion in another topic regarding framerates related to length, I would probably be better off with a teensy rather than an arduino, since I will be dealing with 800 pixels?
I would of course also be interested in the usb FTDI solution that pburgess has hinted at, since the animations will be synced to a soundtrack playing on a computer, so the microcontroller would only be relaying data from the computer anyway.

In another project, I want to work with a 15m long strand, but I think I might need to double it to get a high enough light output. So in effect I want two 15 m strands to work as one. I assume I can´t cheat and use the same clock/data lines to two strands? Could this run as two parallel strands from one controller, and how precise would this be (it would be very visible if they were not completely in sync).

Thanks for any advice!

hc

[pburgess]

I'd suggest one long strand for this, yes. The benefit is that it simplifies keeping everything in sync. And a USB-native microcontroller, either the 32u4 Breakout Board+ or the Teensy, will make for much better frame rates (the Uno, etc. are only good for about 100 pixels before animation starts to get jumpy).

And yes, actually you can cheat and run the same clock/data lines to multiple strips in parallel! There's probably some upper limit to this, but with two strips it seems to work without a hitch.

[hcgilje]

Great, thanks!
I just found a place where I could order the Teensy in Europe (http://www.pieterfloris.nl/shop/), so looking forward to try this out.
I will try the parallel trick tomorrow.

[hcgilje]

Out of curiosity, would the FTDI control option you have mentioned involve the bit bang method you described on Hackaday quite a while back?

[pburgess]

Yep, it's FTDI bitbang mode exactly. I have the beginnings of a C library on top of this for dealing with the LPD8806 strips. This in turn gets a Java JNI "wrapper" so it can work with Processing. Once this is all more polished and presentable I'll put together a tutorial and some demo code; unfortunately some other stuff takes precedence for the time being.

[hcgilje]

sounds interesting. I might want to try to integrate it into openframeworks at some point.