Advice on first build

[trag]

I am planning on building something in the 5mW range for my first build, so I can learn how to do it without the risk of damaging expensive components. I have read the unfinished Build Guide and the "I want to build a laser" thread, so I have a general idea of what I will need to do. I have a few questions before I start though.

I want to use a diode that is high-quality, yet relatively cheap. Is it true that I could most easily meet these criteria with a red diode? On the other hand, it would be nice to have a more unusual color. Ideally, I would like to a 635nm diode, but that might be harder to find or more expensive. I will be looking around, but I would appreciate any advice on specific diodes (of any color) that would be good but cheap, and where to buy them.

Another question I have is about safety glasses. I know that they aren't really necessary under 5mW, due to the blink reflex, but I'm not sure at what point they become necessary. For example, I might decide to get a 10mW diode or so if it's not too much more trouble, and I wonder if glasses would really be necessary with that much power. Would 10mW be safe to use as a pointer around other people?

Thanks for bearing with me! I will probably have more questions in the near future as I plan out the whole build in more detail.

 

[Benm]

Building a 5 to 10 mW laser is easy, because the main parts are readily available. I'd recommend using an aixiz module and driver assembly and powering that from a lithium battery to get started.

As far as safety is concerned: 5 or 10 mW does not pose that great a danger. Just avoid looking into the laser directly or using a mirror whenever you can.

Accidental reflections in windows and such become a true concern once you surpass the 100 mW limit or so. The typical reflection from a house window is in the order of 4%, so it poses little risk for sub-100mW lasers. Looking into an accidental reflection may be unpleasant, but not likely to do any permanent damage to your eyes at reasonable angles.

 

[trag]

Any tips on where to get 635nm diodes? I saw this 5mW one at alltronics.com for $30, but that seems a little expensive. Or do they usually come in the aixiz modules?


Edit: I just found something at modwerx for $4. I wouldn't know whether those are high quality or not though.

 

[AdamCaudill]

Edit: I just found something at modwerx for $4. I wouldn't know whether those are high quality or not though.

I've had good luck with modwerx, fast shipping and items as described.

 

[trag]

I am trying to decide what kind of power source and driver to use. Would 2xAAA with a flexdrive work? The diode I'm going to use needs 2.2V and 40mA, so if I were to use a linear driver, I would need 4.5V, and that seems a little impractical. Another option is 1xAAA with a boost driver, but I'm not sure if one AAA would last very long in that setup, since the current draw would be higher.

Another question: Is a heatsink necessary for something this low-power? I've seen that some people don't use them in 5mW lasers, but is that a good idea?

 

[Kevlar]

What diode are you using? Is it the 635nm you mentioned above? If so, I wouldn't think a big heatsink is necessary, the Aixiz module should be enough IMO.

If you diode only needs 40mA and uses a flexdrive, one AAA would probably give you decent run times.

2XAAA with a flexdrive would work too. You can find the PDF manual for the flexdrive here: http://hacylon.case.edu/ebay/laser_diode/Micro_FlexDrive.php

 

[trag]

Yeah, as of now, I'm planning on using that Samsung 5mW SLD635... from modwerx.

If I used 1 AAA, the voltage would never be over the 2.2V required, so I would just need a boost driver, not a flexdrive, right? Or would there be some other advantage to a flexdrive in that case?

I'm thinking 2xAAA might be overkill for something so small. It wouldn't be bad, but it seems like just one AAA would provide more than enough runtime. I mean, you buy those cheap laser pointers and they have tiny button cells in them. Granted, this would probably consume 5x as much power as those.

 

[Kevlar]

The flexdrive is a buck/boost drive. So if your power supply is over the required voltage of the diode it will "buck" the voltage down to what the diode needs. For example, your diode needs 2.2V and you use a 3.7 - 4.2V power supply (1 Li Ion battery), the flexdrive will lower the voltage of the power supply to what your diode requires.

Say your doing a blu-ray build with a PHR 405nm diode, you could use a 3V power supply and it will "boost" the voltage to the diode (~5V).

But the minimum voltage you can use with a flexdrive is 2.0V so is you wanted a 1XAAA build I would suggest using a Li Ion battery (size 10440) with would supply 3.7V to 4.2V.

Every driver has it's own specs so you will just have to read the data sheet to see what the input and output voltages are.

Drlava's flexdrive and boost drives are some of the most common around here.

 

[Morgan]

I think you'll also find that the minimum output of a Flexdrive is 65mA. This, I suspect, will be too much for a 5mW diode and kill it. You may get lucky and successfully overdrive it but it'll output more than the stated 5mW.

M

 

[Kevlar]

I think you'll also find that the minimum output of a Flexdrive is 65mA. This, I suspect, will be too much for a 5mW diode and kill it. You may get lucky and successfully overdrive it but it'll output more than the stated 5mW.

M

Good catch Morgan!! Sorry Trag, I don't know where my head was!! All I kept thinking was Voltage. :banghead:

 

[trag]

The minimum output for both the flexdrive and micro boost is 65mA, and my diode takes 40mA. I guess I could use a linear driver with a 3.7V lithium. Drlava's linear driver would drop out if the supply voltage got to 3.4, but the battery would die before that.

It would be nice to use 1 regular AAA though so I don't have to buy a new charger. Are there other boost drivers besides Drlava's?

 

[Morgan]

There may be but probably not to found here. You may get lucky with a flashlight driver but they are not a stable as laser diode drivers. I would bite the bullet on both things; upgrade to 3.7V rechargeables of the size you're after or ones that are commonly used and; go for a higher power diode. Pulling old DVD rewriters will probably get you a higer power red and likely cost you nothing if you go to your local PC repair shop and beg a few broken ones.

I think you're asking a lot for a first try but don't let that stop you if you want to crack it.

M

 

[trag]

You have a good point. For all this trouble I might as well go higher than 5mW. I'll think about it.

 

[Morgan]

Thinking about it trag, the single AAA, (or AA), greenies must have a low dropout boost driver. They will almost certainly be too high a current output for 5mW of red but you might be able to find one cheap enough to remove the driver after you've had fun with the green, (or after it dies!)

M

 

[trag]

I realized that since I don't have a soldering iron or multimeter, I could easily spend $70 to build something that would cost less to buy. So I might just come back to this project later in favor of buying a laser or two.

On the other hand, I haven't seen very many 635nm lasers for sale, if any, so it wouldn't be too pointless to make one of those. I could also pay a few dollars more for a driver with a preset current so I don't need to get a multimeter right away.

 

[Morgan]

You do have those options, yes.

M