My first DIY laser diode array - honing the details

[DIY9000]

Hello everyone,

I am very new to electronics but I have done a lot of research and would like your assistance on finalizing my setup.
My goal:
An array of 16 evenly spaced 635nm 5mw laser diodes that can hold that wattage and wavelength for 30 minutes uninterrupted

Things I know I need:
16, 635 nm 5mw continuous wattage diodes
a laser driver
a power supply
a housing to hold the diodes

I understand there is great variation in diode quality but at the same time I am not looking for top end diodes. I plan power this array with AA batteries and I am only interested in a current regulating driver since cost is a large factor.
My questions are:
Can I use one driver to regulate all the diodes if i link them in parallel and the driver can handle the wattage and amperage?
Where can I purchase cheap but reliable 635 nm diodes and laser drivers? I have seen prices from 2 dollars to 200 dollars per diode.
Since I am looking for a cheap driver, how can I make sure it sends out the correct amerage?

Any other useful information or feedback is appreciated. Thanks everyone!

 

[Cyparagon]

We can help you a lot better if you tell us what you're trying to build.

 

[VisibleGreen]

Yes and listen to Cyparagon. He knows what he's talking about. If you don't understand a term or phrase then don't be afraid to ask what it means too.

 

[DIY9000]

We can help you a lot better if you tell us what you're trying to build.

I'm basically just trying to build a laser array that I can use in low level laser therapy. It needs to be able to give out 635 nm and cover a large area of skin (maybe around 50 cm^2) resulting in around 2-3 joules per cm^2 after 30 mins. Thanks!

 

[RedCowboy]

Yes and listen to Cyparagon. He knows what he's talking about. If you don't understand a term or phrase then don't be afraid to ask what it means too.

Narcissistic antagonist. Is that a laser term?

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@ Diy9000

Many diodes are driven together today because manufacturing tolerances are quite good, but if one diode draws more power than the rest you will have a problem as it will burn out then if your circuit was series they all go out or if parallel the surviving diodes are now getting too much.
One method is to drive rows or groups of diodes together.

 

[DIY9000]

@ RedCowboy

I see. I was planning on running them in parallel, so maybe I can drive 4 rows of 4, using 4 different drivers... I've searched a lot and I am still no closer to finding the components I need (at a reasonable price) I saw DTR's webstore, but unfortunately they only have 638 nm, not 635 nm and the power output is much too high for my purposes.

 

[RedCowboy]

Ebay is awash with all kind of this, China makes what you are looking for turn key, or you can source parts, they typically have good deals because of all the competition.

laser therapy | eBay

 

[DIY9000]

Yeah I have scoured Ebay but there is no product out there that meets my specifications. Most are LEDs and not lasers and the lasers that are out there either have the wrong wavelength or are simply glorified laser pens. There are commercial products that meet my specifications but are only sold to medical practices and are tens of thousands of dollars. I must build my own.

 

[VisibleGreen]

Narcissistic antagonist. Is that a laser term?

I was being sincere

 

[Pi R Squared]

Try these, they have built in divers: 635nm Lasers, AixiZ
This place sometimes also has low priced 635nm diodes: https://mi-lasers.com

Alan

 

[DIY9000]

Alan,

Thanks for the response! I did come across the AixiZ website. I didn't know the modules came with built in drivers. I am hesitant to purchase them on account of the lack of information (e.g. mA range, divergence, temperature...). I want to make sure I can safely run the lasers. mi-lasers is a new one to me, looks promising although it doesn't appear they sell drivers and the modules are a little too pricey.

 

[DIY9000]

Actually, I miss spoke it looks like they do sell a driver. https://mi-lasers.com/product/acc-laser-diode-driver-kit-2/

They say the current is adjustable, so I take it that will depend on what resistors I sodder onto the board and what voltage I attach to it. Since they don't tell me what resistors they have I am not sure how flexible it is.

So putting, let me know if this makes sense.
A sample setup: I will purchase 2 diodes https://mi-lasers.com/product/5mw-635nm-laser-diode-hitachi-hl6312g-2/ which use 55mA and link them in paralle. Since they are linked in parallel I need to set the driver (https://mi-lasers.com/product/acc-laser-diode-driver-kit-2/) output current to 109 mA (I would do 110 but the range ends at 109 mA). This should give 54 and 55 mA to the diodes. Using a 9 volt battery I need to set up 82.56 Omhs of resistance in the driver so the output is 109mA.

 

[DIY9000]

Does that make sense? If so, the only other things I may have to concern myself with is temperature regulation and consistent power. I assume if the current is consistent then the diodes will maintain their 5mW output, but I realize this may change if the temperature rises. And I do need these diodes to run for 30 minutes continuously.

 

[RedCowboy]

5mw diodes are not going to make much heat, the drivers will make more heat than the diodes.
There is usually enough internal resistance in red LD's that 3V of alkaline's can't hurt them, I have many that run on 2 AA's and that's it, just a switch and put them in parallel. I have some 5 or 7mw 638's or 635's and 2 AA batteries in series runs them just fine as the internal resistance won't let then draw too much current. I don't know what output is.


Here's diodes and drivers of the 635nm variety 5mw
http://www.ebay.com/sch/i.html?_fro...0.X635nm+diode.TRS0&_nkw=635nm+diode&_sacat=0

 

[logsquared]

When driving laser diodes in parallel best practice dictates the use of ballast resistors. 1 ohm non-inductive in series with each LD.

As mentioned above, if one dies open the other gets 2X the current.

I would recommend series if l possible.