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Topic: addressable I2C i/o chip recomendation? (Read 2035 times) previous topic - next topic

davivid

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.

robtillaart


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

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

davivid

Thanks for the suggestion but the datasheet says:
Quote
Address by Three Hardware Address Pins for
Use of up to Eight Device


I ideally need up to 127 devices

robtillaart

#3
Nov 16, 2011, 08:24 pm Last Edit: Nov 17, 2011, 09:10 pm by robtillaart Reason: 1
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  :smiley-red:
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

macegr

Only 8 MCP23017 chips per bus, and each Centipede has 4 chips :)
Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

CrossRoads

Use MAX6953. One chip. Control 140 LEDs.
I2C interface.
One current set resistor.
http://datasheets.maxim-ic.com/en/ds/MAX6953.pdf
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

davivid

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).

florinc

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.

KirAsh4

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.

KirAsh4

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

davivid

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.

KirAsh4

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.

davivid

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

KirAsh4

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.

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