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How to; Select Your Laser Parts

Hiemal

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Hey guys. Another HOW TO from me. :)

So, you've decided to become interested in lasers... and you're looking at a PHR-803T sled for sale on Modwerx.com, or maybe Cajunlasers.com...

For $10, you don't see why not, but you don't know how to drive the darn thing?

You'll need a constant current driver.

What is it?

It's a certain type of regulator that will push a specific amount of current (amps) through anything. It will adjust the voltage output as necessary to maintain said current output.

Well, okay, but what do I use?

It depends on what kind of laser you're building. Typically all hosts (that is the thing you'll be putting your laser in!) use either one or two lithium batteries which provide a nominal voltage of 3.7 volts. If it's single cell, use a boost driver, or a buck-boost driver.

If it's mult-cell, then you can use a buck driver or a linear driver.

But why are there so many different types of drivers?


Well, because not every laser diode is the same. Some have higher forward voltages (or, voltage drops) than other ones.

IR laser diodes have a Vf around 1.9 to 2.2 volts. (780 nm and above)

Red laser diodes have a Vf around 2.3 - 3.4 volts. (this is 635 nm to 650 nm)

Blue laser diodes have a Vf around 4.3-4.8 volts. (this is for 445 nm and 450 nm diodes)

Violet laser diodes have the highest Vf of all the diodes. They drop anywhere from 4.5 volts all the way up to 6 volts. (405 nm, PHR diodes drop the lowest)

Typically the more current you push into a laser diode, the higher the forward voltage is.

If the Forward voltage of your laser diode is below your batteries voltage, then you need either a linear, buck-boost, or a buck driver.

If it's above, then you can use a boost, or a buck-boost driver.

There are certain characteristics of each driver, which you can read about here: http://laserpointerforums.com/f67/how-laser-diode-drivers-work-explanatory-thread-71513.html

Another thing to keep in mind while selecting your laser diode driver is if you're using a case negative host. Some laser diodes are case negative, which means the cathode end of the laser diode is tied to the actual case of the laser itself... this may not sound important, but depending on how your driver is laid out, it may spell death for the laser! Linear drivers work perfectly for this, and are always common ground no matter what. Other drivers are also common ground as well, but you'll need to check with which one you're using first!

Another thing to keep in mind is that some drivers have "drop out" which means by default they drop off a certain amount of voltage...

With two cell builds, this usually isn't an issue. However, if you try to power a red laser diode off of a 3.7 volt battery, and the regulator already drops 2 volts, you can see the issue right away. HOWEVER, there ARE linear regulators that drop minimal voltage, and can power IR and RED lasers off of one cell. With boost drivers this isn't an issue, and buck drivers have a minimal voltage drop by default. Buck Boost just combines the two, and they can either push the voltage UP, or DOWN.

But what laser diode do I pick?

I can't help you with that, because it's really comes down to opinion, and budget, and also burning ability, if you like that kind of thing.

Red lasers are typically the cheapest (650 nm ones that is!) and cost around $10 for an LPC-826. This is for 200-300 mW; they burn pretty well, but won't even smolder anything white or light colored.

LPC-826 diodes can handle 400-460 mA for good life and good power output.

Purple lasers are also cheap too. A PHR-803T can be had for $8! They're around 100 mW, but surprisingly they burn better than reds. More of the energy is absorbed, rather than reflected. They can handle around 100-110 mA just fine. There are also higher powered ones, 6x sleds, 8x sleds, and 12x sleds, which can handle 190 mA, 300 mA, and 500 mA respectively.

Blue lasers (445 nm) are the highest powered ones we currently have available to use... However, I do NOT recommend these for a first build. They are class 4 lasers, and are extremely dangerous to eyesight. They are also multimode, which means instead of a nice round dot, they have a more rectangular shape to the output. This means they are typically very divergent, and won't burn at distances. They can be had from $40 to $60 depending on who you buy from, and what series projector they were removed from. As for power, well, the max they can handle hasn't really been established, from my understanding... Anything under 1.6 amps will work. These are some high powered diodes!

There are also 450 nm diodes, which are single mode. They are made by Osram, and can be had for $60. Again, the limits for these haven't been established yet. I'd say 200 mA is decent to use. This will output around 130-150 mW, by the way.

What about IR lasers?


I can't really explain how to use IR lasers, as there are so many different kinds of them that there's really no "standard" or "set" current to use with them. Not to mention, they're also extremely dangerous... They appear extremely dim, or like a dead red laser diode. As a result someone might point the laser into their eye and only see the dim light and end up injuring or blinding themselves with it.

Jeez, blinding themselves? These sound dangerous!

Well, no more dangerous than, say, fire. It just depends on who is using the laser. I completely advocate for laser safety (who wouldn't?), because well, it's needed. Lasers above 5 mW are dangerous to eyesight, and will cause blindness if struck even for a short moment. Depending on what laser color you get, you'll need a respective laser goggle pair. Laser safety goggles made for blue lasers will not protect against reds, obviously.

Amazon.com: Uvex S1933X Skyper Safety Eyewear, Black Frame, SCT-Orange UV Extreme Anti-Fog Lens: Home Improvement

Are a great pair of starting laser safety goggles for BLUE and VIOLET lasers. They're cheap and extremely effective.

As for Red lasers,

Eagle Pair® 190-470nm & 660-760nm Laser Safety Goggles

are around the only choice. There are also OEM laser goggles, which are made of glass if I'm not mistaken. They're definitely more expensive though, but you can't put a price on your eyesight, as I'm sure you've read many times.

Hey wait, I just noticed, you never mentioned green lasers?

Ah, yes. Green lasers aren't actually laser DIODES. They use a system called DPSS, which stands for Diode Pumped Solid State. It's basically a set of crystals, NVO4, and KTP, which are pumped by an 808 nm laser diode to spew out 532 nm light.

And why did you leave it out?

Because these aren't typically DIY'd. They're only made in modules, which are somewhat hard to get a good host for. Usually you just buy a premade laser. You can get one from laserer.com, as well as some other laser reseller stores.

How do I know what kind of battery(s) to get, now that I've chosen my driver and laser diode?

Well, again, it depends on what kind of host you're going to use. Some use 10440 batteries (these are the same size as AAA batteries) and will have a mAh rating of around 300-600 mAh.

Some use 14500 batteries, which are the same size as AA batteries. They have a capacity around 600 mAh, to 1000 mAh.

Some use 18650 batteries, which are the most commonly used ones. They have capacities anywhere from 2000 mAh to 3000 mAh. They are not common to any standard cell size.

There are obviously more types of batteries out there... but seeing as your first build will *probably* use a flashlight host, then the above batteries will work perfectly.

Wait, you mentioned mAh, what is that?

mAh stands for Milli-amp hours. It is the amount of current the battery can supply for one hour before needing to be recharged again.

So, a 2000 mAh battery can supply 2 amps for 1 hour before needing a new charge.

Or you can draw 4 amps, and use it for half an hour. Or draw 1 amp, and it'll last 2 hours.

Okay, so I've chosen my laser diode, battery, host, safety goggles and driver... now what?

Now, you'll need to buy 3 other things, 1 depending on what power laser you're using, and the other two are necessities.

When you buy a laser diode, you'll need something to mount it in... depending on what size laser diode, you can get aixiz mounts for cheap just about anywhere that sells laser items. However, not all laser diodes are the same size. Some are 3.8 mm, (the smallest) 5.6 mm, (standard size) and 9 mm (which are typically IR laser diodes) If your laser diode is not 5.6 mm, you'll need to find a custom aixiz mount.

Secondly, if your laser is powered over 200 mW, you'll want to get a new pair of lens. The lens that comes with a standard aixiz mount is all plastic, and is not AR (anti reflective) coated. Without this coating, more of the light is reflected back into the laser diode causing losses and possibly damaging your laser diode.

Depending on what color you're using, you can get either these;

https://sites.google.com/site/dtrlpf/home/glass-lenses

The G-series lens allow more power output, HOWEVER, the dot is not as clean with the normal AR coated glass ones.

You will also need a battery charger, which you can find easily on eBay by searching "lithium ion universal charger".

Okay... I just ordered everything. Now?

You may need to wait a while, if you ordered something from China. Once everything gets there, you'll also need a soldering iron (which I assume you already have!) and solder. You'll also need some wire, which you can get Accessories : Cajunlasers Store here.

Also, not every laser diode has the same pinout. You'll need to look up your laser diode's number, and see what it has. Most red lasers are "case negative" which means the case pin is the cathode end of the laser diode.

What if I have a problem with my laser?

Check the batteries, and recheck the wiring. You'll also want to check the driver, to make sure it's outputting the correct current using a test load.

If the diode is emitting light, but doesn't seem to be "coherent" or grainy, then the laser has more than likely died, and is now an LED. This may be due to ESD (electrostatic discharge), overcurrent, overvoltage, really anything can kill a laser diode! And there's unfortunately nothing you can do to save him... You'll need to buy a new one. It may not even emit light at all, and still be dead.




And, that for now, is my guide. I hope you enjoyed reading this, and I'll be editing it quite often for a few days.

THANKS FOR READING!
 
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Things

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Re: How to; Drive a Laser diode, and how to build one

Nice guide!

As a bit of a side project to my scanner wiki that is going really well, I set this one up by request: Laser Reference

Maybe if you could sign up and post it there too? :)

The original DPSS primer that got deleted from here a while back will end up on there too eventually.

Just a thought.

Dan
 

Hiemal

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I added some color, and rearranged some things. :)

And Dan, I would but I can't figure out how to post to the wiki! xD
 
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ARG

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@Things I created an account on the wiki, can you give me edit permissions? :)

@Quack Great guide! +1
 
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There are also higher powered ones, 6x sleds, 8x sleds, and 12x sleds, which can handle 190 mA, 300 mA, and 500 mA respectfully.
Shouldn't this be respectively?

Not trying to be a grammar Nazi, just trying to contribute to the thread... :tinfoil:
 

Hiemal

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Ah, yeah. When I was writing it I knew it didn't sound right.

Thanks!
 

n2stuff

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Another great guide Quack. Plus 1 when I can.

Just one correction their are green diodes.

quote:Ah, yes. Green lasers aren't actually laser DIODES
 

Hiemal

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Sure, there's green diodes but ...for someone starting out?...

I don't think they'll want to push $250 for one part, and even then they'll not know entirely what they're doing and may ...break it.
 

n2stuff

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Sure, there's green diodes but ...for someone starting out?...

I don't think they'll want to push $250 for one part, and even then they'll not know entirely what they're doing and may ...break it.
So true. And they are only a very small %, so I would have also not include them in the list. :na:
 

Hiemal

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Exactly; I'm not going to bother including exotics because of so many reasons. :p

Plus people might rage and end their foray into lasers if they break their first one. Lord knows I almost did. :p
 
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This was extremely informative, thank you for the post and I look forward to any others that you may have in the future. I really liked how you basically made a story out of it and used your answers to build questions that would also turn into answers. :)
 

Soren

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Great guide! one small correction though: the gain medium for 532nm DPSS is Nd:YVO4 not NVO4.
 




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