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[on:]

I'm looking for the most efficient(least amperage) and cost effective way to power several 3w RGBs (300-350ma)utilizing 3 Ch RGB DMX controller. Aka, output from controller will have 3 wires (RGB) and ground from 12v controller and want these to connect to the IC (assume it needs 3 separate individual pwm inputs&outputs -- cat4103..etc).  Is this possible, or is there a DMX to PWM module?  if so, I know I'll need to amplify the output current of each channel on the IC to 300-350ma.  Using LM317s per channel might be the most cost effective, but, certainly not most efficient with 3v dropout per module.

[Reply #1 on:]

I did a quick search and the 1st thing I found was the LM3406.   For RGB you'd need 3 of them, and they are surface mount so you'd have to make a board or otherwise deal with that.

If you want DMX, you'd have to program that into your Arduino (and build the interface circuit).

I'm looking for the most efficient(least amperage) and cost effective way to power several 3w RGBs (300-350ma...

... Using LM317s per channel might be the most cost effective, but, certainly not most efficient with 3v dropout per module.

Any switching regulator will approximate 100% efficiency (if properly designed).    That means you can get more current-out than goes in (at less voltage-out than goes in), and almost no power is dissipated by the regulator itself.  The switching circuit is going to require an inductor, which adds a bit to the complexity & cost.

The power loss (and associated heat) with any linear device (like the LM317 or a resistor) depends on the current and voltage drop across the device (P = V x I).   It's not unusual for the regulator (or limiting resistor) to waste more power than goes to the LED. 

certainly not most efficient with 3v dropout per module.

The voltage drop is the difference between your power supply voltage and the LED voltage.    You'll have more than a 3V drop ONLY if your power supply is 3V higher than the rated LED voltage.

[Reply #2 on:]

A TLC5940 will do 350ma out if you combine three channels together. 16 total channels are available. It's a DIP chip. eBay price is around $1.50 or domestically it's around $3.

Here's some links for the Arduino and DMX.

[Reply #3 on:]

Great find on the LM3406... then it would regulate the current appropriately to each color based on the pwm input?  With 6x3wRGBs (18w total per fixture), since LM3406 is rated at 2a could I use 1 per color and only use 3x3406's per fixture?  Aka, 1x3406 blue, 1x3406 green, 1x3406 red.  I don't need multiplexing but only control per color.   I want to use the pwm output from an RGB DMX controller to each IC, as the 3406 will do both logic and voltage regulated pwm signaling...will this work?  

I'm a bit confused on the difference between the 3406 and CAT4109...

With the TLC5940, can I input the pwm signal voltage from the pwm-output of RGB DMX controller?   Basically, I need an IC that can direcly take pwm from an 3CH RGB controller decoder, prefer to use 1 ic per color and/or 3 ic's per fixture versus using 1 for each color on each RGB then be 18 regualtors/ic's (in using LM317's).  I believe the pwm coming from the 3ch RGB controller is 12v > so input voltage on IC needs to be 12v at min, otherwise, would need to regulate voltage down to appropriate input voltage.

I think I'd need another voltage and/or current regulator (mosfet)along with the 1360 to pull it off...

[Reply #4 on:]

Sjim

Have a look at these two items
http://www.ebay.co.uk/itm/Arduino-6-channel-led-shield-3-currents-can-be-set-0-35-0-7-1A-/370745850727?pt=LH_DefaultDomain_0&hash=item56522cbb67

http://www.ebay.co.uk/itm/Arduino-FET-shield-/370593835709?pt=LH_DefaultDomain_0&hash=item56491d2abd][url]http://www.ebay.co.uk/itm/Arduino-FET-shield-/370593835709?pt=LH_DefaultDomain_0&hash=item56491d2abd[/url]

The 1st may help with what you have in mind ??

BR
Graham