Luxeon Star & Laser Diode Driver Module

Looks interesting-

I'd order one now if they had a US distributor or on-line ordering- Guess I'll wait until someone else trys one first since they apparently do not.

Yep, I've been waiting about two weeks to get a few more LM2621 boards from National. Their email reply to me said they should have been available last Wednesday.

Silviron - Regarding the EU-38, The company
does have online ordering and takes payment via VISA, MC, etc. They ship UPS and the like. I would have ordered a couple if I knew that this device might fit the bill. But, first thought I'd throw the idea out to this group.

I'm not opposed to ordering one or two of these devices, but would like an idea as to how they perform. I was real disapointed in the fact that the datasheets were not in-depth.

I've been inside of a couple of dead pocket lasers, but they both had the three contact diode. I wasn't able to measure any voltage
or current. Most likely because the diode was
not emitting a light source for the IC to regulate.

Maybe someone will come along that has knowledge on how these laser drivers actually
work. Better yet, perhpas someone has a cheapo laser that they care sacrifice in the name of LED science.

Mercator

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:


I've been inside of a couple of dead pocket lasers, but they both had the three contact diode. I wasn't able to measure any voltage
or current. Most likely because the diode was
not emitting a light source for the IC to regulate.<HR></BLOCKQUOTE>

This is a different "animal" than the board being discussed above. The third lead goes to a photodiode in the laser, and that's what regulates the current to a value already "pre programmed" into the board.
Simpler than that actually... the diodes in most ~5mW pointers typically thresholds around 30mA (give or take) and has an operating span of ~10mA above threshold.
Go over and the diodes go pop or they radiate beyond FDA regs, go under and the device no longer lases, period.

In any case, I wouldn't expect to get more than around 50-70mA out of one of these, even if you tapped into the PD feedback circuit and started messing with the driver current that way.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
Maybe someone will come along that has knowledge on how these laser drivers actually
work. Better yet, perhpas someone has a cheapo laser that they care sacrifice in the name of LED science.
<HR></BLOCKQUOTE>

There are two problems here.
One is that most "cheap" laser pointers use an unregulated (no photodiode) laser diode on a crude C-mount, and the driver board consists of a momentary switch and an SMD style resistor.

Go above that, and you all of the sudden run face first into the photodiode regulated type that use 5mm "can" laser diodes, and the circuit goes from simple to rediculously complex in some cases.
It uses the signal from the laser diode's integral photodiode as an active feedback, decreasing current when the laser brightens, and increasing current as the laser dims.

You can tell yours is one of these by turning it on and shining a powerful (close to 5mW or greater) laser pointer down the business end. In the vast majority of cases, you'll be able to actually cause the test pointer to turn itself off by shooting another laser pointer down inside it.

Only one of mine is this regulated type; I had bought it for my gun but the dovetail was all wrong, so I just kept it to use as an extra-tough pointer. Every other red pointer I own is the cheap C-mount type, and has only a resistor as its driver circuit.

As long as the board (that is the butt of this topic) can generate the current they say it can, *and* generate it at close to 4 volts *and* is indeed adjustable, it may work. However, most visible laser diodes don't care for a Vf of much more than 2.4 volts... this circuit may limit Vf to similar levels too - someone may just have to spring for one and delight the rest of use with his findings.

Just received my LS and must say, I'm very impressed. The opportunities for unique LED flashlight design are at a new level.

I have been running the LS on a single 1200Ma
rechargeable 3.6v Li-ion battery. This seems like an almost ideal voltage and current combo for the LS. Only drawback is the rechargeable aspect of the battery and I'd like to utilize the LS in several 3 and 4 cell applications.

Looking through this forum I found several people using the National LM2621 Eval board for 3 and 4 cell applications. Something I'd like to do play around with myself.

I went to National's website to order a couple of EVAL boards and found that they are out of stock. I wrote to National, inquiring if the boards are going to still be available and have yet to receive an answer. Has anyone else had to wait on arestock?

I decided that there must be another solution besides the LM2621, so searched the net. I found something that might be of interest. I don't know if this has been discussed in other topics in the past. But, here is something that might be of use for an LS in a 3 or 4 cell design as well as for powering large arrays of regular LEDs.

It's a Laser Diode Driver Module that has an input of 3.0 to 6.0 VDC and the constant output is current adjustable (thru a pot)
in the range of 0 to 1.2 amp. The board is small, 14 x 35mm. This particular module is designed for laser diodes that do not
utilize an internal photo detector to adjust the output current. The pinouts are for 'DC In' and the anode and cathode of the driven
device. The specs on this board are very limited and my knowledge of electronics is even more limited. Therefore, perhaps some of you technos can take a look and lets us know if this driver can be used for powering regular LEDs and the LS. I don't know if the output is oscillating or not and have no idea if this is a practical or efficient
circuit to use as a replacement to the LM2621.

If someone cares to take a look the URL follows. I'm keeping my fingers crossed on this device because it does look promising in
the fact that it's cheap ($15.00), it's small, and adjustable without modifications.

The companies web address:
http://www.roithner-laser.com/

The datasheet on the device: http://www.roithner.de/All_Datasheets/Drivers%20for%20Laserdiodes/EU38.PDF

Mercator

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
Just received my LS and must say, I'm very impressed. The opportunities for unique LED flashlight design are at a new level.

I have been running the LS on a single 1200Ma
rechargeable 3.6v Li-ion battery. This seems like an almost ideal voltage and current combo for the LS. Only drawback is the rechargeable aspect of the battery and I'd like to utilize the LS in several 3 and 4 cell applications.

Looking through this forum I found several people using the National LM2621 Eval board for 3 and 4 cell applications. Something I'd like to do play around with myself.

I went to National's website to order a couple of EVAL boards and found that they are out of stock. I wrote to National, inquiring if the boards are going to still be available and have yet to receive an answer. Has anyone else had to wait on arestock?

I decided that there must be another solution besides the LM2621, so searched the net. I found something that might be of interest. I don't know if this has been discussed in other topics in the past. But, here is something that might be of use for an LS in a 3 or 4 cell design as well as for powering large arrays of regular LEDs.

It's a Laser Diode Driver Module that has an input of 3.0 to 6.0 VDC and the constant output is current adjustable (thru a pot)
in the range of 0 to 1.2 amp. The board is small, 14 x 35mm. This particular module is designed for laser diodes that do not
utilize an internal photo detector to adjust the output current. The pinouts are for 'DC In' and the anode and cathode of the driven
device. The specs on this board are very limited and my knowledge of electronics is even more limited. Therefore, perhaps some of you technos can take a look and lets us know if this driver can be used for powering regular LEDs and the LS. I don't know if the output is oscillating or not and have no idea if this is a practical or efficient
circuit to use as a replacement to the LM2621.

If someone cares to take a look the URL follows. I'm keeping my fingers crossed on this device because it does look promising in
the fact that it's cheap ($15.00), it's small, and adjustable without modifications.

The companies web address:
http://www.roithner-laser.com/

The datasheet on the device: http://www.roithner.de/All_Datasheets/Drivers%20for%20Laserdiodes/EU38.PDF

Mercator<HR></BLOCKQUOTE>


Maxim makes a step up chip that looks promising, MAX756. The MAX757 looks better (variable output voltage), but it cannot be purchased in small quantities.

As soon as I get the parts needed I will make the PCB board and construct the regulator. It will be set at 3.3v output, which should be fine for the LS.

A much more efficient way to regulate voltage would be with the LM2595 step down IC, which is rated at 96% efficient. As it is a step down regulator, it cuts out at about 1 volt above the desired output voltage. I plan to run 12 volts (8 AA's), with this LM2925 set at 3.3v. Should work well. I may be interested in putting together some of these regulator boards to sell, so let me know if you want one, either a step up with the MAX756 IC, or the LM2959 step down.

I have a LM2563 step down evaluation board, and have been running my LUXEON STAR with it, until it overheated and burned out. I was running 3.5 volts, but with inadequate heat sink. I am using it with 4 AA's (12v), and it works great. I need to set the voltage down to 3.2 or so though. I changed R1 to a 10k trimpot, but I also need to change R1 to a 1k resistor. (I couldn't get it to go below 3.5 volts). A decent source of power has been a real headache, but I have finally found a good solution(s).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:

It's a Laser Diode Driver Module that has an input of 3.0 to 6.0 VDC and the constant output is current adjustable (thru a pot)
in the range of 0 to 1.2 amp. The board is small, 14 x 35mm. This particular module is designed for laser diodes that do not
utilize an internal photo detector to adjust the output current. The pinouts are for 'DC In' and the anode and cathode of the driven
device.<HR></BLOCKQUOTE>

Looking at the picture, it appears that the device is a simple linear regulator, with an op amp (perhaps an LM358) driving a power transistor.

There appears to be no inductor, which you'd have for a switching regulator.

I've been designing a step-down constant-current driver circuit for one or two Stars driven from a 12V supply (this is for a non-flashlight application). The efficiency should be around 80-85% for two Stars from a 13.2V supply. There is a minimum supply voltage of 8V or Vout+2, whichever is higher (in other words, driving 3 Stars in series from a 12V battery supply is probably not what you want to do).

You may want to look at Linear Tech's LT1510 (which is what I'm using) or the LT1511. Both can provide constant current and/or constant voltage outputs, though the LT1510 makes a smaller board because it's got fewer external parts and is available in a small-outline 8-pin part.

Is there any interest here in such a beast?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
Looking at the picture, it appears that the device is a simple linear regulator, with an op amp (perhaps an LM358) driving a power transistor.

There appears to be no inductor, which you'd have for a switching regulator.<HR></BLOCKQUOTE>

Yes, you are right, it is a linear constant current regulator. Actually all of these boards.

Thanks to those that replied with several
IC design circuits.

Probem is, I looked at the sugested datasheets and it seems to me that either the output voltage and/or current wasn't high enough, or that the input voltage was to high. Or, there was something that didn't fit my requirments. I plan on designing around a circuit that will utilize the rechargeable 3.6v Li-ion battery. These batteries I have are the same dia, as the 123's and are twice as long. I estimated that without a dropping circuit this battery would drive the LS at 400+ Ma. I first powered my LS with this battery resistored down to provide aprox. 320Ma. This was fine for testing but I don't want to use such an inefficient method in my final design. At 320Ma the LS still ran very warm, so it looks that in order to play it safe something a bit lower than 320Ma would be required. I think I remember reading that the ARC-LS will be running at 300Ma so as not to generate that much heat.

I originally posted this thread thinking that the laser diode driver might be an answer, but from what I've read and from several posts here, I now think that this pre-assembled circuit won't fit the bill. Besides, I wasn't able to locate another source here in the states and the German dealer hasn't taken the time to answer an inquiry regarding additional specs.

From what bikeNoamd and Wayne Johnson wrote regarding a constant current/constant voltage circuit design, I think this is the best approach for me to take. I will continue to look for an adequate circuit. So far, from what I've seen, it looks like perhaps one of the ciruits designed as a single cell Li-ion battery charger might be worth considering. These are a CC/CV circuit that operate at about the correct output range.

I'm open to any and all suggestions. I'm not knowledgeable enough to actually design circuits, but I am proficient in building circuits from schematics and even etching my own simple PCB's I guess you could say I'm more of a machanical engineer rather than a electronics expert.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
I first powered my LS with this battery resistored down to provide aprox. 320Ma. This was fine for testing but I don't want to use such an inefficient method in my final design.
<HR></BLOCKQUOTE>

You will not get better efficiency. If you care so much about efficiency, try to heatsink the Luxeon with a maximum of 15°C/W.

If you use a switching power supply you will get a lower efficiency than with a linear regulator. You have only a couple of 100mV to getrid off. Try a constant current regulator which works down to a minimal drop. How do you protect the cell from over-discharge?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>

I originally posted this thread thinking that the laser diode driver might be an answer,..
Besides, I wasn't able to locate another source here in the states and the German dealer hasn't taken the time to answer an inquiry regarding additional specs.
<HR></BLOCKQUOTE>

Which German dealer? Andreas Roither is in Vienna, Austria. He is as German as Alaska is Russian.
Which additional data do you need (maybe I can answer it)?

In Response to PeLu's reply:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
You will not get better efficiency. If you care so much about efficiency, try to heatsink the Luxeon with a maximum of 15°C/W.<HR></BLOCKQUOTE>

Yes, I do know of the need to heatsink the Luxeon. These guys heat up quickly when driven near max. I guess my striving for theefficiency issue isn't that big of an deal since I only need to current drop of a 100Ma's or so.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
If you use a switching power supply you will get a lower efficiency than with a linear regulator. You have only a couple of 100mV to get rid off. Try a constant current regulator which works down to a minimal drop. How do
you protect the cell from over-discharge?
<HR></BLOCKQUOTE>
So... From what you mention, I should be looking for a circuit that is a constant current regulator . Would this also address the over-discharge problem? If you know of any possible schematics posted on the net, I sure would appreciate a link to them.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Which German dealer? Andreas Roither is in Vienna, Austria. He is as German as Alaska is Russian.<HR></BLOCKQUOTE>

Sorry, I stand corrected. At my posting I didn't remember exactly where he was located. Just the fact that I needed to convert USD from DM's
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Which additional data do you need (maybe I can answer it)? <HR></BLOCKQUOTE>

Well, I guess I was still trying to figure out if this pre-assembled driver circuit would handle my specific input and output voltage and current requirements. The only specs. provided on the datasheet was the the laser current was adjustable up to 1500Ma's. It would sure be nice to be able to utilize something like this pre-assembled board, much in the same way so many builders are using the LM2621EVAL as a quick, simple, cheap and small boost regulator.

PeLu... Thanks for your help!!

Mercator

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
I guess my striving for theefficiency issue isn't that big of an deal since I only need to current drop of a 100Ma's or so.
<HR></BLOCKQUOTE>

Ok, then you will need only some 50°C/W.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
So... From what you mention, I should be looking for a circuit that is a constant current regulator . Would this also address the over-discharge problem?
<HR></BLOCKQUOTE>
No, of course not. You have to do that separate. I've just got a few circuits for low headroom current regulation, but they are all on paper. Will have look where it is available. But maybe a #122 bulb is enough...
Or you may make a simple circuit out of a LM334 and a couple of other parts to 'amplify' current.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Just the fact that I needed to convert USD from DM's
<HR></BLOCKQUOTE>

This will soon be history. Actually I have the first Euro coins in my pocket now (although they must not be available before end of December...)

PeLu Wrote:
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Or you may make a simple circuit out of a LM334 and a couple of other parts to 'amplify' current. <HR></BLOCKQUOTE>

I looked at the datasheet on the LM334. From what I read and from what I've been told, in order to use a current regulator, I would need to start out with an input voltage a couple of volts higher than the needed output voltage. I might have this wrong, so some clarification would help. You also mentioned in your post... "to amplify current". I don't actually want to amplify the current, I need to regulate it down by aprox. 100Ma's If you'll remember, my batttery of choice for this project is one rechargeable 3.6 volt 1200 ma Li-ion. On a fully charged cell the battery could drive the LS at 400+ Ma. I'm begining to think that perhaps in this battery/Luxeon combo, the easiest solution would be to just use a resistor. Something else I might consider is utilizing an oscillating circuit and driving the Luxeon somewhere between 300 and 500Ma. I don't remember reading here if anyone has posted results on this subject, but it would be of interest to know the details. Especially, details regarding over heating at these higher pulsed currents.

Mercator

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
If you'll remember, my batttery of choice for this project is one rechargeable 3.6 volt 1200 ma Li-ion. On a fully charged cell the battery could drive the LS at 400+ Ma.<HR></BLOCKQUOTE>

Well, isn't "fully discharged" considered to be 2.8V per cell? In other words, aren't you going to run out of voltage before you run out of energy? The nominal voltage on the white LS ranges from 2.55 to 3.99 volts at 25 degrees C; your lamp is apparently low enough voltage to light with the battery you have.

You might be able to get down to 150mV drop or so using a low-dropout linear regulator, but it's not going to be too easy. Look for one with current limiting (avoid foldback limiting though); these can be made to do the job, since they typically have lower internal reference voltages for the current limit function (lower than the 1.25 volt bandgap reference for the voltage section).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:

I looked at the datasheet on the LM334. From what I read and from what I've been told, in order to use a current regulator, I would need to start out with an input voltage a couple of volts higher than the needed output voltage.
....
I don't actually want to amplify the current,<HR></BLOCKQUOTE>

OK, I was apparently too brief. You take a resistor which drops the necessary 64mV at the current you want to have and put it between minus and the LED's cathode.
You take a transistor with good beta and the necessary size (power!) in between plus and the LED's anode. The LM334's minus to minus, the sensing input at the LED's cathode and the plus to the transistor's base with a resistor in between (depending on your transistor, maybe 10 kOhm). Usually you will not need this resistor, but when the circuit falls out of regulation the LM334 may draw too much current. It is similar to the application notes page 9. You may have to add a small capacitor to avoid oscilating. And you may pull the transistor base to plus for discharge protection (but the LM334 will still draw current, not ideal).

The datasheet on the device: http://www.roithner.de/All_Datasheets/Drivers%20for%20Laserdiodes/EU38.PDF

Mercator[/QB][/QUOTE]


Schematic for this particular LD driver and quite a few others in Sam`s Laser FAQ: http://repairfaq.cis.upenn.edu/sam/eu38ldd.gif
http://repairfaq.cis.upenn.edu/sam/laserdps.htm#dpssld

Adam

Led-FX

Thanks for the link for more info on the EU38. I know about Sam's site but I guess I didn't dig deep enough to find that he addressed that particular laser driver. Some very interesting reading.

I wish I had waited a day or so, because I went ahead and ordered one board from Roithner. Total with shipping to the US was aprox. $20.00 (US) Not sure how it will preform with the LS but will soon find out. I plan on testing the board and posting the results.

You seem to know some about these drivers. How do you think it will preform? Any ideas on a good circuit or perhaps how one might modify the EU38 to make it more suitable for driving an LS. I quickly read the info on the Laser site and noticed something about a voltage regulator circuit built ahead of a EU38. This might be highly desireable since the LS and all LED's are voltage sensitive.

Like I mentioned.... I don't know how this laser driver will work out, but I like the idea for a pre-assembled, adjustable constant current board. I'm open to any and all suggestions, tips, hints, etc.

Mercator