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1  Using Arduino / LEDs and Multiplexing / Re: "High" Capacity Constant Current Chip? on: February 10, 2013, 12:49:18 pm
Sorry, wasn't clear. It's rated up to 1 A, not at 1 A. The LED current is set by an external resistor.
2  Using Arduino / LEDs and Multiplexing / Re: "High" Capacity Constant Current Chip? on: February 10, 2013, 12:30:33 am
Thanks for the inputs. I'm going to chicken out, and use 8 separate constant current sinks (CAT4101). Rated to 1 A, so power dissipation shouldn't be a problem, and up to 6V continuous LED voltage (25V transient). Thermal protection mode and "zero" current shutdown mode. Even I shouldn't be able to blow these up  smiley-wink.

Will control each channel with a separate digital out from the Arduino; that way, programming will be easier than it would be with three shift register chips. They'll be turned fully on/off, so won't need PWM control (though they support PWM).
3  Using Arduino / LEDs and Multiplexing / Re: "High" Capacity Constant Current Chip? on: February 09, 2013, 10:22:23 pm
Thanks for the link, MIke - I've bookmarked it for future reference. Looks like all the solutions at that current range require one chip per channel, so that may be the way I go.

To answer your question, fungus, I'm planning an 8x8 direct drive LED matrix with LEDs that individually run on either 100 mA or 300 mA, full power (no dimming). Only one LED will be lit at a time, so total current draw at any time from all the LEDs will be that 100/300 mA figure. Will control it with an Arduino.
4  Using Arduino / LEDs and Multiplexing / Re: "High" Capacity Constant Current Chip? on: February 08, 2013, 02:19:47 pm
Plus, finding anyone who sells that 150 mA chip (Mos-Tech MT508) has proven to be difficult. If anyone knows of a dealer who might carry these ...
5  Using Arduino / LEDs and Multiplexing / Re: "High" Capacity Constant Current Chip? on: February 08, 2013, 01:59:25 pm
Combine two channels on that chip...?

Thought of that, but have gotten conflicting answers as to whether that would work or not. Doing it with one chip would also be a bit easier.
6  Using Arduino / LEDs and Multiplexing / "High" Capacity Constant Current Chip? on: February 08, 2013, 01:32:14 pm
Anyone know of an 8-channel constant current chip (driver or sink) capable of more than 300 mA per channel? Highest I've been able to find is an 8-channel sink chip capable of 150 mA per channel.
7  Using Arduino / Project Guidance / Re: HIgh-current LED driver question on: February 08, 2013, 01:22:38 pm
Never mind - got an answer (maybe), but figured out a better approach.
8  Using Arduino / Project Guidance / HIgh-current LED driver question on: February 03, 2013, 02:14:03 am
Hi all,

I've thought of a project where I would like to drive a matrix of high power LEDS, 8x8, one at a time continuously(but no more than one would ever be on at a time). I thought the Colorduino might be an easy solution for this, as the product page states:

- 24 constant current channels of 100mA each
- 8 super source driver channels of 500mA each

This would be perfect for my high-power LEDs as they're spec'ed for 100 mA operating current at 3.4V, 120 mA max at 3.6V. However, digging deeper into the full Colorduino specs:

http://itead-europe.com/pm/platform/mainboard/colorduino/DS_IM120410004_Colorduino.pdf

it says that the maximum drive current per dot is 58 mA. It's designed to drive an RGB LED matrix, so I assume that each dot refers to a single LED color at each position in the matrix. So what I'd like to know is, can the Colorduino actually put out 100 mA per channel, or is it limited to 58 mA? And if the limit is 58 mA, could I connect two constant current channels at 58 mA to a single LED connection to give me 116 mA? Any advice you can give me on this, or on any other way to drive a high-current 8x8 LED matrix one LED at a time, would be really appreciated. Thanks!

- drjeopardy

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