Ok, I already know this is WAY over my head already, but I want to build a light display using multiple LED's. The problem I am facing is I can't seem to find any controllers that interface with a PC that will tell me how many LED's they will drive. They tell me how many channels they have, but never how many LED's the controller will drive per channel. Is there a universal amount of LED's able to be run on say a 16 channel controller? Any help would be very appreciated. Also, if anyone has a schematic of a large scale controller, or even a small scale controller that can be PC based, if you are able and willing, I would love one. I know a little about electronics but I have a LOT more to learn. If it's not the most difficult schematic to follow, I might be able to build one, and save myself a ton of green. Thanks for any help you might be able to lend.

 

After about 2 seconds of Googling on dialup, I came up with: 24×24 LED dot matrix display control - Scientific, embedded, biomedical, electronics contents.

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Hi! Welcome to the forum.

I think you mostly need to define your terms first. When you say "controller", are you talking "lighting controller" as in stage lighting, or room lighting, or some other thing? Do you have any links/model names etc which could help us know what kinds of things you're looking at?

Some other things it would be good to know in order to help you:

How many LEDs will be in the display?

What kind of display is it? i.e. random single blinking lights, scrolling message, random blinking groups of lights, etc.

How would you like to control it? From a PC or microcontroller?

To determine what you can run per channel, you need to look at the output voltage and amperage available on each channel.

Anyway, just hoping to get some more information so that we have a place to start.


Torben

 

I apologize for being vague. I work in a dance club, and I am planning on building a large 'sign' aprox. 20x5 feet in dimension. In the middle I will put the name of the club (in LED's) aprox. 4x2 feet and around the outsides I want randomly blinking (fading in and out) LED's. In effect, it will have the name of the club surrounded by blinking stars. I'm still deciding if I want the name outlined, or a full array. If I do a full array, I will want to be able to control from my PC or laptop certain ways the LED's will act. (i.e. change colors if I use RGB, or a quick scroll of fading LED's to signify a shine or 'bling' effect) If I end up outlining, I will only need to control maybe a color change, or possibly a chase style outline. But I want control via my PC as to be able to change it on command. I figure I will need up to 1000 LED's with the outline, and many more if I do the array. Thanks for any help you can lend. Like I said, I am pretty new at this, but I am a 'do-it-yourselfer' because I LOVE to learn new things.

 

OMG that will be very hard & sacrificing lot of time & work.Better buy it from a signboard manufacture.But it will almost cost highly.

I have done LED sign boards (with user defined characters) but not that huge size.

If you need to display only your dance club name then I'll suggest you to make letters from the LED's & control them via a control circuit (can do without any micro controllers).

When it comes to LED matrix system it will be too complicated.

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If needs be, I will just make the outline stable and have the stars blink using micro controllers. I would prefer to do it the way I want (obviously) but will sacrafice if needs be. Either way, I would like to figure out HOW to do it because I am not really on a budget. I know it's possible, just need to know if it's worth it.

 

You might be interested in the way the Christmas lighting people do their displays. They use cascaded serial in parallel out shift registers. A single bit from a micro shifts the pattern into the registers, the pattern is then used to illuminate the LEDs. One such chip is the 74HC595 Shift Registers With Output Latches. Each will control 8 LEDs so you will need a lot of them.

I would hook a string of these chips to each bit on a port. Eight strings of 16 595s would control 1024 LEDs.This will let you blink the lends in any pattern.

To dim/fade the LEDs you need to do pulse width modulation. In short to do PWM you turn the LED on and off quite fast and to the eye it seems to be on but not at full intensity. The on-off ratio of determines brightness.

Google for "Olsen 595 controller" or "595 Christmas". Since you will be running LEDs you will only need a resistor and a LED connected to the outputs on the 595s. If you want more power then the 595s deliver you can use a transistor to power each LED. There may be a version of the 595 with more drive but I can not remember the number. Anyone?

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BCHS/3v0's Tutorials
Junebug USB PIC programmer kit., USB Bit Whacker,
The 15 Minute Printed Circuit Board! (+drill time)

 

Some "sinking driver" versions of the 74HC595 are the Micrel MIC5821 and the Allegro A6821. Both, if I recall correctly, will 'sink' up to 500 ma at 50v.

Mike

 

I looked at a few sites describing the Olsen 595 Controller and it looks pretty interesting. One question I do have about this. (Again, a Noob ?) If I were to use RGB LED's, I would have to triple the amount of 595's correct? They all use the same Cathode, but the anodes would have to be on separate ports. Although this really isn't a problem, per se, just a lot more work. (probably worth it in the end tho)

 

Exactly.

What you want to do is simple in nature for a micro controller project, but the scale is so large that it will get ugly if you are not careful. Start small with a pair of 595's and a 18F pic to get a feel for it on a small scale. Figure out if you need transistors to make the LEDs brighter learn a little about coding the program. FWIW I found 74HC595's at Newark for 20 cents (SMD) or 23 cents (DIP) in 200+ quan. The big cost is going to be the 1000 3 color LEDs.

After looking at what you need to do buying a ready made unit may sound good.

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BCHS/3v0's Tutorials
Junebug USB PIC programmer kit., USB Bit Whacker,
The 15 Minute Printed Circuit Board! (+drill time)

 

Evil Mad Scientist Laboratories - Peggy version 2.0

This a customizable 25x25 (625) LED sign board kit ($95, less LEDs, another $50-$100+).
Uses Atmega168 (same as Arduino), completely open source. Every LED is individually controllable, and can be any color (mix or match). Can even do 14x14 RGB...

Posted this link, as it should be useful to see how to control a lot of LEDs, and just getting several kits would save you a huge amount of time and money. I saw this last week, and thinking about getting one, just for the Conway Life demo (always liked that on the computer, one of my first assembly language projects on the Commodore 64).

 

You can put any color LED anywhere in the Peggy array, but Peggy doesn't use multicolor LEDs.

How much current do you plan to use per LED?

 

Not very much current at all. Maybe 1.5v at the max power. I work in a dimly lit club and I don't really need my sign illuminating the whole thing. LOL!

I actually changed my mind a little bit. I think instead of using the RGB (which would be awesome, but overkill for my application) I am going to, instead, go with UV LED's because blacklighting is very prominent in all aspects of my club, maybe some blue, and white ones as well. This has changed my design ideas a little bit more.

As far as the name in the middle, Is it possible to run them ALL off a single port on the 525? In essence, making the PC (or micro controller) think of them all as a single LED rather than 1000 individual diodes? Then I just have to mess around with the dimming on the 'stars' which I understand can each be run off a micro controller to do the task of dimming. Is this correct?

Thank you all for the help you are giving. Without you guys, I would be in WAY more over my head than I already am. HAHA!

 

Also, these are the types of LED's I'm planning on using.

Lot of 100 X 5mm UV LED Ultra Bright Free Resistors - eBay (item 370050637203 end time May-17-08 02:27:07 PDT)

 

Not to be a downer but that might not be a great idea--UV LEDs don't look all that bright but if you look straight into them you can get a lot of light focussed on the retina which doesn't provoke a blink/avoid response and doesn't trigger the iris to contract.

Although in a club situation I'm thinking it might be mounted high enough that nobody can look straight into the display. Is that correct?

There are some interesting notes on this page.

Putting a bit of fluorescent paint on the tip of each UV LED seems like a neat way to both make it look cool and make it safer.


Torben