4 Lasers current question

I'd like to switch 4 Red 5mW lasers on/off independently using 4 digital pins on the Arduino Duemilanove.

Laser Specs: Operating Voltage: 3.0-5.0v (6.0v Max) Operating Current:15mA at 3.2V+ rising to a maximum of 30mA at the trigger voltage which is around 2.8-3.0V

I read that the max current on each output pin is 40mA so it would seem that I can run the lasers directly from the digital pins but I just wanted to check I haven't overlooked something and this isn't going to damage my board?

Thanks for any advice you can give.

This correct, 15 mA is O'K with arduino, you can drive all 4 of them simultaneously. Additional resistors may be necessary, if there is no constant current source on the lasers boards ( link to specification?), to make sure current isn't over the limit

Thanks for your reply. I'm using the red laser module OFL6 details here : http://odicforce.com/shop/page/16?shop_param=

I'd really appreciate any advice on whether a resistor is required.

It has constant current built in however a 125 ohm resistor wouldn't hurt to ensure it stays within spec and offers protection if something fails or shorts

if you think they can somehow short circuit, you can always place a fuse in between the laser and you arduino. that will make sure nothing can burn your arduino...

It has constant current built in however a 125 ohm resistor wouldn't hurt to ensure it stays within spec and offers protection if something fails or shorts

Well, constant current woun't work with resistor, as it will "cut" overhead to regulate, even LDO regulator needs at least 0.5V. Probably, better to test module separately with +5V and multimeter, and if all as spec. says, than install w/o resistor.

if you think they can somehow short circuit, you can always place a fuse in between the laser and you arduino. that will make sure nothing can burn your arduino...

Never heard about 40 mA fuses, are they exist?

You can get PTC resettable fuses in a variety of currents. How about one like this? http://www.digikey.com/product-detail/en/B59990C0080A070/495-3905-ND/651953

So long as it draws the expected current it will operate properly, and if it does draw too muhc it will dim or shut off but it shouldn't and that would mean something failed

You can get PTC resettable fuses in a variety of currents.
How about one like this?
http://www.digikey.com/product-detail/en/B59990C0080A070/495-3905-ND/651953

OMG, thanks for pointing me, I was not aware, 14 mA trip current , unbelievable.

So long as it draws the expected current it will operate properly,

No, with 20 mA current arduino pin outputs voltage drops to 4.2V, laser hold 2.8V to operate , it’s leave 1.4 for constant current driver to maneuver. With R = 125 , V = 125 x 0.02 = 2.5V. That hardly enough to light up, probably it wouldn’t.

Maybe try the resistor and see its affects, best solution anyway would be to use a transistor and garuntee not burning an I/o pin