Need some LED Circuit help for a hobby project...

On a sunny day (Mon, 07 Feb 2011 14:36:12 -0600) it happened "V4Vendetta636" wrote in :

Serial in - serial and parallel out shift registers are very useful. You can clock in any combination and shift it at any speed. If you clock at very high speed then you can update the whole thing at once from for example a micro processor. An other advantage of shift registers is that you already have enough power to drive LEDs, say 8 per shit register.

Alternatives would be cheap PICs, or even a FPGA, the last would need drivers, both would need programming.

Buy some cheap 74HC... shift registers and couple of LEDs, and play with those to see how you can shift in ones and zeros using some switches for data and clock. Once you have mastered that, start thinking about how to make those switch signals electronically. Or / and learn to program PIC micro controllers.

And in case you haven't realized this yet... even if you have 150 LEDs, but all you want is a "chase" pattern with, e.g., a couple LEDs on and three off, the pattern will repeat every 5 LEDs, so you only need to implement the logic to control 5 LEDs and then copy those signals to the other 145 LEDs.

That being said, sometimes you find that the "copy those signals" circuit implementation (i.e., driver chips) requires just as many parts as hanging each and every LED off its own shift register (and then not needing additional drivers).

Joel Koltner expounded in news:DfZ3p.364342$ snipped-for-privacy@en-nntp-07.dc.easynews.com:

Around Christmas time I saw there were Christmas strings with an intelligent controller being sold. Someone else decoded the signals and hooked it up to an Arduino (or AVR). I couldn't find it just now, but google might be your friend. Probably the cheapest/easiest way to achieve your goal.

Warren

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I don't know where you're located, or how much money you want to spend, but this might be an excellent time to pick up a Parallax "Board of Education" at Radio Shack. It is an inexpensive micro controller package that will teach you how to program a Basic Stamp.. You can control LEDs in a variety of patterns (it has 16 input/output lines), monitor switch closures, control servos, and a lot more. There are a lot of things that are easier to "fiddle with" in software, rather than by changing hardwarte.

Topology???? A project to create a 150' string of lights might have a very different solution from one blinking a 10x15 array

0f LEDs on a single circuit board. Current required per led might also be a useful specification. 30mA/lamp is 4.5A to switch in flash mode. Can you leave the lights enabled and switch the data fast enough? Or do you have to turn the lights off while programming? And you don't want the FCC field agent showing up at your door 'cause you blanked out radio reception two blocks away with your 150' antenna.

You have a lot of "system" parameters to define.

I would suggest you google "picaxe" or visit

It is the simplest and cheapest way to use a microprocessor. If you want to save money you can be smart about it and not but any of there kits - you just have to make up a cable, and interface circuit (2 resistors), download the free software and buy a single chip (08M will do what you want but you might prefer 18M2 or 20M)

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I like your friends's suggestions, and I think the perfect shift
register/LED driver for your project would be an Allegro A6276, data
sheet at:

http://www.allegromicro.com/en/Products/Part_Numbers/6276/6276.pdf

Don't worry about the lifetime buy deal, Newark has 10309 of them in
stock at:

http://www.newark.com/allegro-microsystems/a6276ea-t/ic-led-driver-constant-current/dp/87K3398

for USD 2.64 each, so a 160 LED display would cost you $26.40 for the
drivers.

If you don't want to, or can't, use a microcontroller to run the
thing, then there is a solution which might be more expensive in terms
of hardware, but which doesn't involve trying to ride the learning
curve.

What do you want to do?

On a sunny day (Mon, 07 Feb 2011 20:04:28 -0600) it happened John Fields wrote in :

That is a nice chip.

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Indeed. :-)

Here's another beauty; an oldie that refuses to die:

http://www.national.com/ds/MM/MM5483.pdf

Thank you all for the info. Will begin doing some research based on your responses.

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On a sunny day (Tue, 08 Feb 2011 18:25:27 -0600) it happened John Fields wrote in :

Yes, saves some parts. I have used the Philips i2c version in the past: