TEC Labby Rig

Hey guys. I'm starting my first laser project. This is going to be both my build thread and a place to ask for advice :yh: I wanted to make myself a temperature controlled rig for plotting the characteristics of different diodes. I've been wanting to build a cooling system like this ever since I found out about TECs. I'm feeling pretty good about that part of the project.

I'm less sure about my diode selection. First of all, yes I WILL be buying goggles. I don't need a ton of power. I don't need to burn anything, and don't care about color (although I kind of think I should maybe avoid IR for now). I don't even really much care about the beam quality. I just want a cheap diode that makes enough heat that I can actually make sure my cooling system is working properly. I would like to eventually test the diodes to failure, after getting as much data as I can from non destructive tests. The 5mw reds that are everywhere would be good, except that they are a practically negligible thermal load. As far as I can tell I need something producing a few hundred mW. I would like to buy 5-10 diodes for less than $100, but the price is flexible as I'm not yet sure this is a reasonable budget. The 5mw reds that are everywhere would be good, except that they are a practically negligible thermal load. The only diodes I have found that meet my current price and power requirements were 808nm which I am open to if there aren't other options, but I'd rather stick to a visible wavelength. I was hoping that someone here might know of a few options that fit these requirements. If there is any information I've omitted that should be included please let me know!

Look for some lpc-815 or lpc-826 diodes. They are 660nm red and right about the power you are looking for. They can be found for about $10 a piece usually.

Edit:
$10.99 from o-like (China)
300-400mW brand new red laser diode/extracted from LPC-826 [OL-LPC-826] - $10.99 : Zen Cart!, The Art of E-commerce

About $11.40 from odicforce (EU)
LPC-826 658nm Red Laser Diode 250mW+ - Detailed item view - OdicForce Lasers Online Shop

$14 from laser66 (US)
Creative Technology - LPC-826 Laser Diode Page Creative Technology - Your source for diode lasers and laser modules at green, red and other wavelengths.

$9.66 from aliexpress (China)
660nm 300 400mW CW Red Laser Diode LPC 826-in Other Consumer Electronics from Consumer Electronics on Aliexpress.com

And of course there are some deals on ebay if you look around.

Thanks! Those look damn near perfect, and easy enough to find on ebay. I'm having trouble locating a datasheet for them though, is this something I could reasonable get ahold of? or not for these diodes?

Any other diodes I could look at that are slightly more powerful? I just want to know my options before settling on one. I could mix and match a bit too

I don't see one for the 826 but you can find one for the 815. The 826 is a fairly recent diode and it handles more current that the 815.

For cheap power the 826 is you best bet. The next step up for power would be the 300mw Mitsubishi 635nm diode or the 12x 405nm diode. Both diodes are much much more expensive.

ok thank you very much, this is exactly the type of info I was hoping to get. I'll get my BOM straightened out and hopefully get a few more details up here in the next couple days!

Does anyone have any experience with the 836?

Ok I got 10 LPC-826 on ebay for $60. I need to select a driver for them. I've been reading a lot about how sensitive they are to drive, is a typical (but cheapish) benchtop supply sufficient? Does anyone know of any drivers capable of operating from 12V or 15V? I noticed most of the drivers in pointers are designed to operate from just a couple cells, so I think it may be hard to find what I am looking for. I'm not interested in a linear driver, if I want one of those I'll just make one.

I've got the TEC setup mostly figured out in my head. I'm going to mount the diode into a small copper block mounted on the cold side of the TEC. The hot side of the TEC will connect to a copper cold plate. The coolant will circulate through a second cold plate with a TEC on each side. The hot sides of these two plates will each have an aluminum pin fin heatsink and a fan. It will all be controlled by a little micro controller, probably an arduino to start. I realize this will provide a significant amount of cooling power. These first diodes should barely make use of this, but I will be able to test them at very low temperatures, perhaps as low as about -10 to -20 fahrenheit.

I know lasers can be dangerous. As I have little experience actually working with them, it's tough for me to gauge the actual risk of for example looking at the spot. What about seeing the beam? or the reflection off a piece of glass or perhaps a wall painted with glossy paint? Just trying to get a reasonable feel for things before I start. :thanks:

Jeffrey said:

Ok I got 10 LPC-826 on ebay for $60. I need to select a driver for them. I've been reading a lot about how sensitive they are to drive, is a typical (but cheapish) benchtop supply sufficient? Does anyone know of any drivers capable of operating from 12V or 15V? I noticed most of the drivers in pointers are designed to operate from just a couple cells, so I think it may be hard to find what I am looking for. I'm not interested in a linear driver, if I want one of those I'll just make one.

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For your purpose, a bench supply on constant current mode should suffice. You just need to operate it correctly... Temperature will change the diode Vf so its interesting to measure it. Together with a thermometer @ the diode (LM35 if you're into electronics, 1mv/ºc, there is a fahrenheit version somewhere).

Jeffrey said:

These first diodes should barely make use of this, but I will be able to test them at very low temperatures, perhaps as low as about -10 to -20 fahrenheit.

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-20F is around the max temperature difference a common TEC will maintain (considering 104F as hot-side temp...), but I'd not recommend it, because condensing will happen inside the laser... The LPC series are open can diodes! And the facets/semiconductors don't like water too much.

Jeffrey said:

I know lasers can be dangerous. As I have little experience actually working with them, it's tough for me to gauge the actual risk of for example looking at the spot. What about seeing the beam? or the reflection off a piece of glass or perhaps a wall painted with glossy paint? Just trying to get a reasonable feel for things before I start. :thanks:

Click to expand...

People starting the laser hobby commonly used those diodes, extracted from dvd burners. Considering you're careful, its a good start, with a balance between "power and safety". Just don't point it on your eye on reflective surfaces.

That is a beautifully simple little temperature sensor. I was planning to use the TMP36 but the LM35 looks really nice too.