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Author Topic: I2C for longer distance LED light bar system  (Read 680 times)
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I am a veteran programmer and somewhat familiar with electronics. I have an Arduino Mega 2560 microprocessor. I am wanting to build an industrial application which will consist of 5 foot long “bars” each having 4 LEDs. I need the ability to daisy-chain these bars out from the microprocessor and control any combination of turning on/off the LEDs on each bar. I am considering using I2C with extender boards http://sjtbits.com/i2c-to-differential-breakout-board/ but need some serious help in understanding if this is a practical design. The LED “bars” will be about 8 feet apart and on my application there will be a total of 24 bars each having 4 LEDS. I am considering using CAT5 wiring and connectors to daisy-chain and hopefully carry enough voltage to drive the system. Thanks for any advise on how to build such a system.
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Manchester (England England)
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Yes that looks a good way to go, it should work.
Not cheap though, looks like you need one on each end.

What power are your LEDs? Have you got the power side sorted out?
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I am a veteran programmer and somewhat familiar with electronics. I have an Arduino Mega 2560 microprocessor. I am wanting to build an industrial application which will consist of 5 foot long “bars” each having 4 LEDs. I need the ability to daisy-chain these bars out from the microprocessor and control any combination of turning on/off the LEDs on each bar. I am considering using I2C with extender boards http://sjtbits.com/i2c-to-differential-breakout-board/ but need some serious help in understanding if this is a practical design. The LED “bars” will be about 8 feet apart and on my application there will be a total of 24 bars each having 4 LEDS. I am considering using CAT5 wiring and connectors to daisy-chain and hopefully carry enough voltage to drive the system. Thanks for any advise on how to build such a system.

That is a pretty standard NXP chip that cost nowhere near the 20 bucks they are looking for it.  You might want to look at DMX it's pretty much 485 serial and much better suited for going the distance since it's primarily used for theater work.  Cost should be similar if not cheaper than the i2c option your looking at.  Check out http://www.pathwayconnect.com/content/view/91/26/ for the standard pin outs you can put power over pins 4 and 5.
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I use Shiftout to TPIC6B595 shift registers ( each can sink 8 outputs ( latched ) of 150mA )

I drive up to 20  x  7 segment displays spaced out over 3 or 4  meters or so with no problems.

I only use 4 pins of the 328, 3 for shiftout , and one for PWM the blank pins of the TPICs for dimming.

I link up the 12 v LED supply seperately.

The Shiftout is fast enough for what I need, and I use ribbon cable between the various displays, with no data degaradation at the last display.
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Quote
That is a pretty standard NXP chip that cost nowhere near the 20 bucks they are looking for it. 

Silasmoeckel, I think it’s important to be aware that our I2C Differential Extender Breakout Board (see: http://sjtbits.com/i2c-to-differential-breakout-board/) has more than just the NXP PCA9600 chip.  This board not only increases the I2C bus capacitance, but also minimizes interference from outside sources through differential signaling. 

That being said, we have now manufactured this board in large enough quantities that we can lower the price to $10.  We look forward to continuing to serve the community.

Regards,
Matthew Magnuson
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