Driving LED strips directly from a PC?

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

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dbannister
 
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Driving LED strips directly from a PC?

Post by dbannister »

I'm brand new at this. I've looked around the site but haven't found an answer yet. I have never worked with an Arduino or Raspberry Pi and am a complete newby with them.

I would like to drive some LED strips based on live data that is changing on my PC. I can write whatever PC software is needed but I don't know hardware. Is it possible to connect the LED strips directly to a PC through a USB or something so that I won't need intermediate driver hardware like an Arduino? I wasn't sure if the FTDI Serial TTL-232 USB Cable would allow me to do this.

I figure the PC should be able to do everything an Arduino can do and the data is on the PC so it would be cleaner to drive the LEDs from the PC rather than dumping the data to an Arduino and from there to the LEDs.

Any suggestions?

Thx.

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adafruit_support_mike
 
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Re: Driving LED strips directly from a PC?

Post by adafruit_support_mike »

It sounds like the FadeCandy board/software would be the best solution for you:

https://www.adafruit.com/products/1689

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dbannister
 
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Re: Driving LED strips directly from a PC?

Post by dbannister »

That appears to be just what I'm looking for.

Thanks!

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dbannister
 
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Re: Driving LED strips directly from a PC?

Post by dbannister »

I'm up and going with the FadeCandy board which works like a charm and is allowing me to drive some LEDs directly from my PC. So far so good.

Next question - I'd like to drive some LED strip lights that are about 20 feet long. I purchased a couple of meters of the medium density strips (60 LEDs/m) and am distressed that I can't drive more than the first 64 LEDs on the strip. I have the strip connected to the first port on the FadeCandy board. The tech specs say you can only drive 64 LEDs per port so I suppose that's not shocking. But then how can I drive all the LEDs?

The only way I can think of is to break the strips into 1 meter sections and string an extra run of wires to drive each subsequent one. This feels incredibly nasty with piles of extra wire. Do I really need to run 7 sets of progressively longer control wires all connected back to the starting point and then affix each 1m strip so it looks like it's all one piece? What if I wanted to do 100 feet?

Do you have a better suggestion on how to accomplish this?

Thanks.

Doug

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adafruit_support_mike
 
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Re: Driving LED strips directly from a PC?

Post by adafruit_support_mike »

dbannister wrote:What if I wanted to do 100 feet?
That would be a significant engineering problem.

First, every foot of 60-per-meter NeoPixel strip consumes up to 1A of current, so 100 feet would present a current load of up to 100A. Even with the voltage at 5v, that's still 500W, so you'd need to consult an electrician licensed in your area.. for knowledge of local fire codes if nothing else.

Second, the copper traces along the strip aren't anywhere near large enough to carry that kind of power. Our NeoPixel Uberguide talks about the effects of voltage loss along the strip when you get to lengths of 2m or more. We recommend connecting power taps every meter or so.

Third, you'd have timing problems. The driver chip inside a NeoPixel only accepts data to pass along the strip for a certain amount of time before it resets. The WS2812 datasheet says you can run strings at least 1024 pixels long, but 100' is about 30.5m, which translates to about 1800 pixels.. well above the datasheet limit.

Given that 20 feet is still about 6 meters, you'll probably need several power taps to make the strip work at all. You can run a data signal with each tap and control the strip in 1m segments from a FadeCandy, or you can look at generating the control signals from a microcontroller like an Arduino.

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dbannister
 
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Re: Driving LED strips directly from a PC?

Post by dbannister »

Appreciate the response. You raise several good and valid points and I'll look at chasing them down.

I'm basically looking for a solution for commercial applications such as lighting a bar, or a trade show booth, or putting a strip of chaser LEDs around a hockey rink. That sort of large scale project. I can deal with the power supplies along the length. Do you know the distance limitation of cabling from a FadeCandy to a strip of LEDs? Would it help if I ran it over CAT5 or 6 cable?

Thanks.

Doug

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