Multiple 50mW green laser modules wiring

Hi,

I'm currently trying to build a laser harp for my senior project using nine 50mW green laser modules. They have to be powered up all at once, using a power supply (not batteries). My big question is: is it at all possible? If yes, should I wire the modules in parallel or in series? Do I need any resistors? What kind of power supply should I use?

Technical Specs for each module are as follows:

Operating Voltage: 3V
Operating Current: <280mV
Output Power: 50mW
Wavelength: 532nm

Currently I am able to power up two modules directly from the Arduino Uno board without any resistors, and everything works just fine. But when adding the third module, it doesn't work.

Here is my plan to power up all the modules: Use 12V 3A power supply such as this in conjunction with a step down power supply module such as this (just to solder them together). In (my) theory this will give me a constant voltage of 3V 3A. So, if I wire the modules in parallel, voltage will be constant (3V), while current will be additive (.28A x 9 lasers = 2.52A).

Am I wrong? I'm a complete newbie to all this stuff, but fascinated with it and willing to learn as much as I can.

Any help/critique will be greatly appreciated!

By the way, here is my test of the two modules.

Thanks a lot!

Yup, in concept that should work. You might consider buying some adjustable step-down modules like these.

They're adjustable so that you can get "exactly" 3V or so just so you don't strain your green laser modules. I would also use more than one (that link above is a 5-pack) so that you have more wiggle room for current.

Beware that 50mW can be dangerous for your eyes and those of your audience. If you use lower-power lasers and use a fogger to see the beam it'd be a safer alternative.

Bionic-Badger, thanks a lot for your feedback! One more quick question: do I need any resistors in the circuit? Ohm's law gives me 10.71Ω for every laser module (3V/0.28A), and since there going to be 9 lasers wired in parallel, total resistance will be approximately 0.84Ω. Should I still put a 100Ω resistor between every laser and ground, or it's not necessary?

No. The modules will handle all that.
Just wire them in parallel groups and you
will be fine. And make sure the lasers are
firmly mounted and terminate on the LDRs.
We really don't need laser beams going
everywhere and possibly into an audience.

Great, thank you! I already built an enclosure prototype out of pine, MDF, and plywood:



The neck is hollow and the lasers will be placed there facing downward, to eliminate possible eye damage. I'm planning to secure the modules in place by either using threaded rods, or by milling the precise holes on the CNC.

Any reason for 50mw specifically? Also, the beams should terminate inside of a closed space, such as a small chamber where the dot is not visible to avoid eye damage. 50mw is not particularly dangerous, but I guarantee that you'd regret being careless with it, especially if there are 9 of them.

In a darkened room (subdued light, not meaning completely dark), 50mw ought to work, cool.