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[on:]

Hi,

Can any one recommend an addressable I2C chip for driving an LED.

My requirements are: set the address (0-127), drive a single LED (on /off), low cost.

(I found this http://uk.farnell.com/jsp/displayProduct.jsp?sku=1564917&CMP=e-2072-00001000&gross_price=true, which I think would be suitable except I do not believe you can set the address)

cheers.

[Reply #1 on:]

something like - http://www.sparkfun.com/products/8130 - ? 
datasheet - http://www.ti.com/lit/ds/symlink/pcf8575c.pdf -

[Reply #2 on:]

Thanks for the suggestion but the datasheet says:

Address by Three Hardware Address Pins for
Use of up to Eight Device

I ideally need up to 127 devices

[Reply #3 on:]

you can add 8 of such chips, every one can control 16 lines (=16 leds)

8 x 16 = 128 , so you have one to spare.

Another option might be the centipede shield - http://macetech.com/store/index.php?main_page=product_info&products_id=23 -
IIRC there can be two on the I2C bus (eight in fact but the library only support 2, but you may fix that

2 x 64 = 128

hopes this helpes,

update: removed wrong info 

[Reply #4 on:]

Only 8 MCP23017 chips per bus, and each Centipede has 4 chips

[Reply #5 on:]

Use MAX6953. One chip. Control 140 LEDs.
I2C interface.
One current set resistor.
http://datasheets.maxim-ic.com/en/ds/MAX6953.pdf

[Reply #6 on:]

sorry I should of been more clear - I need around 120 individual units, after further research I guess maybe ATtiny45's might be the solution (creating BlinkM clones) although a little overkill for my application, as I only really need a single colour LED (possibly with with PWM).

[Reply #7 on:]

Here is an alternative to BlinkM:
http://www.seeedstudio.com/depot/grove-chainable-rgb-led-p-850.html?cPath=156_157
You can build it yourself, but it won't be much cheaper. Plus, I think you may get a discount when you buy 120 of them.

[Reply #8 on:]

Do you have to be able to set an address for each LED?  What if it's just a 2-wire communication where you shift data out to the entire string?

Take an RGB LED - $0.12 (1000 minimum)
with a WS2801 - $0.16 (1 to 1000)
1x 0.1uF cap - $0.03 (100 - 499)
3x resistors - $0.02 (100 - 499)
PCB - $0.72 (12 - I created my own through fab house)

And you end up with a pixel cost of $1.09 - multiply that by however many you want.  Your Arduino just needs to provide a DATA and CLK source and you're done.  You can either provide VCC/GND from the Arduino (3.3V up to 5.5V), or from an external supply.

Worth nothing: this is the exact same thing that many 5V addressable RGB strips are made of, except for the flexible and adhesive backing.

[Reply #9 on:]

Actually, never mind.  You indicated you're creating BlinkM clones, so these might not be sitting together in a long string.

[Reply #10 on:]

thanks for the replies guys, yes the reason I'm thinking blinkM style devices is because my project requires a tree/branching style layout  - and so chainable units would make for somne ugly wiring.

[Reply #11 on:]

Then, if you're talking each unit being on its own, what does it matter if they're addressable or not?  Just program each one and go to town with them.

[Reply #12 on:]

As I need to be able to turn each unit of and on independently, from the control application.

[Reply #13 on:]

So they will be wired together then, just not in a long continuous string, correct?

You could still do strings, just several of them going to individual branches.  Each one would need 2 wires from the controller (NOT including VCC/GND).  I get what you're saying though.