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ArcticMyst Security by Avery

can you regulate mA without the LM317's 5v> rule?

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Aug 26, 2007
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I love the LM317 for my lasers, but its kinda difficult to cope with the 5 volts and up rule so it works.

Is there any current regulating driver you can make to use 3 volts? Cause the aixiz modules and lots of pen lasers only use 3 volts and they still regulate the output.

Anyone know how those pen laser drivers work?
 





IgorT

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Re: can you regulate mA without the LM317's 5v> ru

Phazonx said:
I love the LM317 for my lasers, but its kinda difficult to cope with the 5 volts and up rule so it works.

Is there any current regulating driver you can make to use 3 volts?  Cause the aixiz modules and lots of pen lasers only use 3 volts and they still regulate the output.

Anyone know how those pen laser drivers work?

Actually it is 6V and up "rule" for red burners, and 8V and up for Blue Rays.. 5V and up would work for IR LDs i think, because they have a lower Vf.


The AixiZ 5mW laser diode driver simply uses the photo diode inside the can, to adjust the current through the LD, and keep the optical power constant. Because of this, it can work from a small voltage, and keeps output the same with various input voltages. I tested between 2 and 5V, and the output was the same, and so was the current..

Otherwise, there are many lasers, especially pen type pointers, from cheap to expensive, that don't use any regulation whatsoever, even when they have a photo diode.. Those work not much different, than just putting a resistor in series, even tho they have enough components on board to achieve PD regulation...



But i think i know what bothers you.. The need for so many batteries and their size..

You could use two AAA size rechargable Li-Pos (10440), which would give you 8.4V when full and 6V when almost empty, which is perfect for the LM317 driver and a powerfull red burner.. For a Blue Ray, you'd need three..



Or you could go with a buck/boost converter, that can regulate the current from an input voltage lower or higher, than the input. This is what i'm using in my lasers now, and it works from one Li-Po or even two Ni-MHs..

I also like my lasers small and as powerfull as possible, and with some help of various people here, i managed to build a suitable driver.. I was dreaming about this for a while, and now it finaly works.

With this one, it doesn't even matter, what voltage the LD needs, it will automatically give it just enough to reach the current you set with a resistor, and you don't need more batteries if it's a Blue Ray... It can work with 5.5V and down to 2.2V input voltage, and the output stays the same in this entire range.



Look at these two threads:
- This is where we were discussing and testing the various possibilities: http://www.laserpointerforums.com/forums/YaBB.pl?num=1194375801
- This is my first laser powered by the SEPIC converter: http://www.laserpointerforums.com/forums/YaBB.pl?num=1204645706


It works great, and i'm gonna use this driver with all my future lasers, so i can power them from a single AA or AAA size Li-Po and make them small, without giving up current regulation or power.

I did have to etch my own boards tho, and the IC is very hard to hand solder, because it has no leads.. Otherwise, it's not that complicated.



If i'm not mistaken, a very similiar driver, with an extra capability or two should soon be finished and sold by Dr_Lava.
 




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