Home made Drivers vs.

Hey !
I've really been enjoying the hobby, building hosts & drivers, lurking on the forum reading much of the great information that has been shared.

But I wonder if the drivers I am building with the LM 317 w/ cap & diode for protection and tested with a dummy load are as safe to use as the 1 Watt one that Aixiz and others are selling for around $14.

My gut tells me (pee ew!) that the smaller ones I can buy like the one listed in the second link below are safer than what I can make (first link below, 3rd pic down).

The driver I'm building is the 3rd picture down: Laser driver - It can be done

Comparing to this one: 1W 445nm blue laser diode driver / 405nm laser driver - eBay (item 380324933736 end time Mar-23-11 14:01:41 PDT)

SO, is my driver really as safe to use as the ones I can buy for <$20?

My apologies for not giving better links...I'm litterally falling asleep as I type...
I would like to credit ROG8811 for the info, as this person seems to have put a lot of good information together! I'm not sure I did that right!

Cadsixohtwo

Cad602;

The LM317 driver is perfectly safe ! !

I have built several of them. It will require two lithium cells for power.

The boost-driver that you referenced is safe also,

but it does have the advantage of being able to operate off one 4.2 VDC lithium battery.

I am partial to the single #18650 cell for my builds.

LarryDFW

Hey thanks for the reassurance! I wanted to be sure before I endeavored to make as small a driver as I could with these "full size" parts.

c602

I would actually tend to think the opposite.

I would put a DIY driver based on the LM317 (assuming you wire it properly!) on a higher pedestal than the $14-ish O-Like, Aixis, Rayfoss, etc boost drivers.

Specifically, because those drivers are inconsistent. I've got two of them here, and one results in ~500mW, while the other ~700mW, with the same diode / lens / battery on the same LPM (tested one after the other).

That's not ideal at all. While that may seem like a "power" issue and not a safety one, what if you used it to drive a 405nm diode that had a max current that you could exceed with a driver outputting 700mA, but not 500mA ? The variable quality might blow your diode.

To your question - I feel much safer with a DDL home built circuit than I do with the "inexpensive" $15 boost drivers from Aixiz etc. The lack of consistency is what scares me. I know that if I put a 1Ohm resistor in a DDL circuit using a LM317 / 1117 / 1084 / 1085 etc, it will never exceed 1,250mA (etc). It might not hit that if the batteries can't handle it, but at least I'm not left *wondering* what current I'll see next.

Obviously you loose the "boost" function, but if your host is 1x 18650, it's easy enough to just use 2x 16340s. If you choose an LDO regulator instead of the LM317, then you can efficiently power any diode we've got access to. So really, you're only in trouble for single-16340, single-CR2, etc hosts.

Ack My last post dissappeared - or maybe my connection died but oh well. I won't even try to rememebr.

I want a laser turtle - I mean, I feel even more confident using the LM 317 based circuits. I've been collecting diagrams for other circuits and I think I want to make other variants as well...I can't wait to get some free time tonight to get busy!

csix02

Welcome to the forums, Cad602
The main advantage of laser drivers you can buy seems to be size and convenience.
There are other ICs you can use to make constant-current drivers suitable for laser diodes. The one I'm looking at now is the LM2621, which is capable of boosting, so you can drive diodes with a higher voltage drop (445 and 405nm) from a single cell.

The main advantage of laser drivers you can buy seems to be size and convenience.

Click to expand...

There is also the energy efficiency issue, a linear driver (e.g. lm317) loose the ecces voltage as heat.

MoonShadow said:

The one I'm looking at now is the LM2621, which is capable of boosting, so you can drive diodes with a higher voltage drop (445 and 405nm) from a single cell.

Click to expand...

MoonShadow:
If you put together a working schematic, I will semi-love you forever. To my knowledge, nobody has put together a good simple DIY schematic for a boost driver. The general explanation I hear is that the only ICs that can do it are surface mount and too small for DIYing.

I just don't buy that - Primarily because voltage boosting just seems to be such a common requirement that there has to be a way to do it properly without crazy surface mount stuff. Having said that, I'm not even concerned about having to solder some of the surface mount-ish ICs (the one you linked to looked doable).

I just don't have the knowledge to digest datasheets and circuit examples efficiently to create a working circuit prototype. But I sure wish someone would

If you're going to tackle something like this though, why not start with an IC that can handle more than 1A load current? (or perhaps design your circuit to use parallel ICs!)

Cheers

Hmm... Well, I don't think there is an IC like that in a through-hole package.
What I'm thinking now is that it's definitely possible, but it requires you to wind your own toroid, and the component count goes up considerably.
I'll have a stab at it today.

MoonShadow said:

Hmm... Well, I don't think there is an IC like that in a through-hole package.
What I'm thinking now is that it's definitely possible, but it requires you to wind your own toroid, and the component count goes up considerably.
I'll have a stab at it today.

Click to expand...

I am intrigued to think we could soon be building our own boost drivers!

I had to google what a toroid (in eletronics) is - to think I was going to be an EE when I grew up instead of what I became...

c