635nm vs 650nm

[Ablaze]

Having three pins when only two of them seem to be used confuses me. What is the third pin for? Why is it there?

 

[rhd]

Having three pins when only two of them seem to be used confuses me. What is the third pin for? Why is it there?

That depends on the diode (the third pin can be different in each case), but quite often (like with 445nm diodes) the third pin is neutral. It doesn't connect to anything inside the diode. All it does is provide a solder-able lead that is electrically connected to the case of the diode. So you can ignore it if you want, but you can also use it if your application requires sending electricity through the walls of the module itself (frequently the case in portable lasers, where the battery at the back of the host sends it's feed to the module through the aluminum host walls).

 

[Cyparagon]

Other times, the third pin might be connected to a photodiode to provide feedback for the driver.

 

[rhd]

Other times, the third pin might be connected to a photodiode to provide feedback for the driver.

Is the photodiode ever used in fiber optic communications to read the light pulses coming at the diode from the other end of the fiber? (IE, for receiving information?)

 

[tsteele93]

There's nothing inherent about the 635nm wavelength that makes the dot any worse than 660. You're comparing apples and oranges (IE, a multi-mode Mitsubishi 635, to a single-mode LOC 660nm. You may have missed his previous reply:



Ablaze is comparing apples and apples. Single mode vs single mode. The dot won't be an issue, they'll both be the same. The 635 will have the same beam characteristics as the 660

The whole "crappy dot" phenomena has nothing to do with the Mitsubishi 635s being 635, and everything to do with them being "multi-mode" not "single-mode".

Thanks for clearing that up for me. I'm not sure how I came under the impression that all 635's were the flat line with wings. I guess that I've only been looking at the high powered ones and assumed that all of them were that way.

Still got a lot to learn.

 

[BShanahan14rulz]

They usually use something fancier for reading data, don't they? i.e. instead of a photodiode, you often find a sensor with more than just anode and cathode pins. These you can also find in those weird oval diodes with the clear block diffraction optic glued on the front, the ones with 12 pins. I'm thinking that photodiode probably used for sensing output from the other facet. Neat idea, though, and I wouldn't be surprised if they used or start using a form of those strange diodes we find in cheap drives as described above for telecom use.

 

[Ablaze]

If you're using the heavy duty black modules (Aixiz sells 5 for $15), then you don't even need a diode press, you just need your fingers to twist a little brass nut in place.

I'm sorry, where are these modules sold? I've been looking for hours and I can't find any pre-assembled units. The problem isn't putting them together, the problem is finding the right parts when I don't know what the right parts are.

Could you help me out on this? Give me a name to look for maybe?

 

[bennett326]

AixiZ 5 pack 15x50mm for 5.6mm diodes Housing Blanks, AixiZ :beer:

edit: also get one of these http://mohgasm.com/index.php?main_page=product_info&cPath=5&products_id=23 they rock

edit#2 fck that you dont need the diode press for those modules

 

[rhd]

No, that's the best part, those don't require a press!

Don't go linear for your driver though, your gloves probably need efficiency.

I can help you figure out a driver. What are your specs? I'm assuming you run your diodes in series, but what's the battery pack voltage?

Edit: what driver have you been using previously ?

 

[Ablaze]

The battery pack is 3.6v peak. The 5 modules are run in parallel.

I wonder if it would be possible to use one driver to drive all 5 diodes. That could potentially save a lot of space.

I have no idea what driver the green modules use, just that they run on 3v+.

One configuration I would like to implement would be to use one diode and module of higher power and split the beam into 5 fiber optic cables. However, I have never seen anyone mention even trying that, so perhaps it would be infeasible.