First build & a few questions

Hey this is my first build I am planning on doing; I branched off in the 'welcome' area of this forum into asking technical questions which still haven't been answered! I figured this 'general' section is the right place!

I have a bit of engineering experience :evil:, and I have a nice selection of parts at my house, so it IS cheaper for me to make a laser rather than buy one. I have searched around this forum and I have a good plan on how to build my laser pointer.

I want to make a laser pointer with adjustable focus (for both burning and distance). I have a working laser diode from a 24x DVD+RW drive (spec online says it's 2.4x, but does that even exist?? It's an older drive and not well-documented, so maybe these descriptions I have seen are probably wrong).

So, I have a few quick questions:
1) What is the best focusable optical housing for the price? I don't want to spend much.

2) Secondly, how important is duty cycle when running the diode at high output (say, 250mW)? I don't know the model of diode I have, so what is a good but effective ballpark for a good duty cycle value (in microseconds and %)? I have seen 30ns or ~40% or less (MAX) recommended on some sony models after searching datasheets.

3) Also, how do I use heat-sinking if I have the diode inside that pre-assembled housing? (P.S. - I already have a good heat sink it came with).

I can build all necessary driver/regulation circuits and I have a microcontroller I can use for the best protection of the delicate laser diode. I plan on adding thermal shutdown/regulation, a timer (no operation longer than 5mins continuous at a time), and PWM (AKA duty cycle; if necessary) using the microcontroller.

I appreciate your help! I hope I can get these questions answered and start making this really cool laser pointer! :yh:

DIYMaster said:

So, I have a few quick questions:
1) What is the best focusable optical housing for the price? I don't want to spend much.

2) Secondly, how important is duty cycle when running the diode at high output (say, 250mW)? I don't know the model of diode I have, so what is a good but effective ballpark for a good duty cycle value (in microseconds and %)? I have seen 30ns or ~40% or less (MAX) recommended on some sony models after searching datasheets.

3) Also, how do I use heat-sinking if I have the diode inside that pre-assembled housing? (P.S. - I already have a good heat sink it came with).

I can build all necessary driver/regulation circuits and I have a microcontroller I can use for the best protection of the delicate laser diode. I plan on adding thermal shutdown/regulation, a timer (no operation longer than 5mins continuous at a time), and PWM (AKA duty cycle; if necessary) using the microcontroller.

I appreciate your help! I hope I can get these questions answered and start making this really cool laser pointer! :yh:

Click to expand...

1. aixiz modules. i carry them at modwerx for ~3$

2.depends on heatsinking but when overdriving diodes you WILL shorten the diodes life

3. there are many machinists on the forum that sell pre-made heatsinks of alum or copper. aixiz modules are ~12mm in diameter so you will need a heatsink to fit.

hope that helps!

p.s. id like to see that driver in action when/if you get it made!

2.4x Speed exists and it's ofc not 24x. I doubt you will be able to get 250mW from this diode. Buy a LOC from modwerx.com together with the aixiz module. Also, don't use the heatsink from the driver, also, forget about the idea of using the assembled heatsink, bigger heatsinks are needed.

Well. without any information on the drive. We can "guess" what current should be used on the type of diode. Red diodes usually come in 5 common types found in drives.
3.8mm - useless unless you can made a custom module for it
Flat diode - also not much use...

Long Open Can - These are the most popular, and are usually ran at 420mA to get 250mW

Short open can - These are not as strong as Long Open Can, and is best to stay under 300mA

Long Closed Can - You can tell these apart because the silver "can" is noticebly longer than the IR diode that is usually in the sled with it. - These seem to be just as strong and also run at 420mA

1. You need an Aixiz module for your diode. Pick one up at modwerx.com
You can also get a glass lens wwhich will increase the output over the stock acrylic lens that comes with the module.

2. Heatsinking is always a good idea, exspecially if your oging to be pushing it to the 250mW mark.
Heatsinks are made to slide over the Aixiz module, which are 12mm in diameter, and usually have a set screw to hold it in place.


as for using a microcontroller to drive the diode.....i don't have that kind of experience to comment on it....

Thanks for the quick replies!

Here are some pictures of the diode w/ heasink I have. I believe it is a short closed can (by closed I am guessing you mean it has a little glass window covering the hole? Mine does). Hopefully this will help!






What do you think this one is capable of? I kindof wanted to use what I already have. BTW: I hooked it up to 2 AA's without regulation (probably bad, I know; I know not to do that now after reading online) and used the focusing lens that was in the optical tray assembly to test the power of the diode. I simply held the lens at the distance at which the beam was focused to a very fine point, and it immediately started to burn little marks on my black keyboard! Here's the lens:



It's very nice; I'd imagine better than the crappy ones in the Aixiz modules.

Well....
I'm surprised it didn't die from the AA.
Did it get really hot from it?

I'm not sure, but the entire are area surrounding the diode on the heatsink was cool to the touch. Plus I only ran it for about 5 seconds.

matts right.. im surprised you didnt kill it with the AA's either. batteries are completely unregulated and a laser diode needs a strictly regulated current or risk diode death. you need to make sure what kind of drive it came from. if you can do that we can help you better but without that info we would be guessing...

Aha! Here's the exact model I got it from:

AOpen Global

you have a low powered dvd burner on your hands.. you may be able to get 50-100mw from it but i dont know what current you should run it at.

DVD+RW/+R Write : 2.4X

Ndrew you are very right. I just hooked it up to regulated 3V (EXACTLY 3V), with brand new, high-capacity rechargeables, and I squeezed 150mA (not mW) out of it according to my multimeter. This equates to probably ~80mW according to this chart: 650nm SF-AW210 Closed Can Red Diode in HeatSink [SF-AW210 Red in HeatSink] - $9.75 : High Tech DealZ, Simplifying the LASER Hobby!

Looks like over at modwerx.com you've got a really good deal on the LPC-815 diode in heasinked host module w/ focus ring, so when I am not poor any more (soon...) I will buy that from you haha.