[Cyborg] 200 laser diodes

[Christoph Maier]

On Wed, 2010-06-02 at 23:06 -0700, Eric Boyd wrote:
> Indeed!  My plan is to basically hack a North Paw board into doing the 
> work, but according to my calculations you should just be able to use an 
> Arduino.  50mW laser diodes.  If we assume they have a 3V drop (the page 
> says "battery: 3-5V"), that means 16.7mA each, which you can drive with 
> an arduino pin.  Anyone know the total power an Arduino can drive/sink? 
>   I'm just wondering how many of the pins you could have going at once...
> 
> Eric

According to 
http://www.atmel.com/dyn/products/product_card_v2.asp?part_id=4198
http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf
chapter 22, Absolute Maximum Ratings, 
you can draw up to 200 mA through the power pins 
and 40 mA through any one I/O pin, 
meaning that without a driver, you shouldn't try to drive more than 10
laser diodes directly. 
(Note that an earlier version of the data sheet quoted 300 mA absolute
maximum rating; this means that you can probably get away with driving
more current for a prototype, but NOT repeat NOT for stuff you want to
sell commercially.)

Christoph