Question About the BDR-209 900mw diode?

So I purchased a 900mw 405nm module from DTR, Came with a acrylic lens replaced that with a 405nm coated 3 element glass lens. Set my driver to 6.36v @ 670Ma, This diode is a beast. burns better than my 2w blue laser. Could be do to better energy absorption on material with that wavelength and or the near round shape of the beam. Anyway. My naive self was using an led driver, This one to be exact https://www.ebay.com/itm/5A-Lithium-Charger-CV-CC-buck-Step-down-Power-Supply-Module-LED-Driver-New-M296/401461074483?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2648

It died after about 30 minutes of solid use. Just suddenly turned off:cryyy:

I know 405nm diodes are very sensitive. I'm going to build a LM317 based driver, My question is is there any extra protection I should include for this diode it being 405nm? And whats the recommended current for builds on this diode? I think 670ma may be pushing its limits for extended use.

Here are some beam shots of it when it was working.
I'm designing a 3D printable threaded host, Its going well so far. The fins on the heatsink i'm using lets air through the host which helps with cooling. I just had the top piece made in the pics. And no, The final host will not be pink.

An LM317 based driver was fine when we had only 200 mW diodes to drive, but you would do better not to use it for more powerful lasers like 1 and 2 watt ones. Because they are linear drivers, you waste any extra voltage from your source as heat dissipated by the driver IC. You will do better with a boost driver for a BDR-209 diode and it can be run at 550 mA for a decent output power.

Also depends on if you want it portable and your power source. On paper those LM317 drivers are good up to 1.5 amps provided ample heatsinking is provided and you have the voltage to drop and power to spare (like powering it from a mains source).

Then again it IS a very inefficient design as it requires 3 volts over the LM317 plus 1.25 reference voltage to work within specification at all, so at 0.5 amps you're obligatory burning off over 2 watts, and probably a bit more.

This doesn't mean linear regulators are done for though, you can build them with low drop out regulators intended to keep constant voltage, and build them very well with opamp/mosfet drivers if your supply voltage is not that much higher than the diode forward voltage (e.g. running that diode from 2 lithium cells in series).

Yeah, I assumed he was wanting this in a pointer. I still use linear drivers depending on the diode. If you have a case positive 505nm diode, the Blitz Linear driver works for this and you don't need to isolate the diode as that driver is continuous positive. Still have to use two Li-ion cells, but not having to isolate the diode makes it worth using that driver.

Thanks for your replies everyone. So the great thing about the host i'm designing is that I can build around my hardware and not the other way around. And to answer your question, yes I am wanting a portable not a lab. But I could always build a lab laser in portable form I love 3D printers!

So wouldn't driving a higher powered diode with a lm317 leave less wasted voltage because the load is using more of it? If I drove a less powerfull diode with an lm317, wouldn't that leave allot of extra voltage compared to driving a diode that's lets say is set @ 1.5amp "445nm". It makes sense that it would convert extra voltage into heat. But It doesn't make sense to me how something that draws less power, would burn off less voltage. Unless your referring to running it off of 1x 18650 which would make sense as 1x 18650 is probably closer to correct output for a diode of lower power,

I know the operating voltage of the bdr 209 is around 6-6.5v. 2x 18650s is about 7.4v
So that mean I need atleast "3v"+"1.5v"= 4.5v for the lm317 to operate. Plus the 6+v needed for the diode. That's around 10 volts. tell me if i'm wrong. Still learning.

Obviously none of this would matter if its being driven off a power supply and not a battery's.

You could use the LM317 as long as the "drop out" voltage, or voltage lost in the regulator isn't too much from the DC input to net you the required voltage for your laser diode, but keep in mind the battery being used, many Li-ion batteries have a range of 3.8 to 4.2 volts from freshly charged to highly discharged (note to Cyp, I'm not saying completely drained). So take in mind if you use that battery, they start out at about 4.2 VDC and drain down to 3.8, or even lower, but I don't let mine go further down, if I realize could be that low.

Also, some of the drivers we use are very efficient regardless of the amount of voltage put into them (above what the diode needs, if they can take it), so you aren't really wasting a lot of power turned into heat with those types of drivers.

Video showing why:

That makes more sense. So the lm317 itself wastes 3 volts from the batteries which isn't efficient because it wastes precious power that could be used to power the diode. On top of the diode needing 6-6.5v by itself which is already above what the batteries can deliver. So that wouldn't work with 2x 18650s at all. I lower powered diode would give allot more "wiggle" room to drive the diode without wasting power. Makes a little more sense for a power suplied lab laser. It also says here that "calling it "Input-to-output differential voltage", giving it a minimum value of 3.0V. That is to say, you should always give an LM317 at least 3V more than you've set for its output voltage" https://electronics.stackexchange.com/questions/214371/lm317-dropout-voltage

So I think I got it. Powering an lm317 with a power supply should work then. 12v sounds about right for this diode. Thanks for the clarification. Please correct me if i'm incorrect with anything I mentioned above.

I may build this laser as a portable laser with a DC input that can be powered from either batteries or a power supply. For now atleast.

Looks right to me, just different ways of saying the same thing, the term drop-out isn't very self-explanatory.

670ma???? well you beat the hell out of it with that current and you are even lucky that lasted 30 minutes with this current and this cheap driver.bdr-209's are running good at 550ma anything more and its risky on every power up to see a nice led. get a proper laser driver and if you are seek to use a cheap driver at least get this one:
https://www.ebay.com/itm/405nm-450n...5nm+driver&_from=R40&rt=nc&_trksid=m570.l1313

its a linear driver so you have to use 2x lithium batteries in series.i have used those drivers many times and seems to quiet stable,never lost a diode,even my s06j still running with one of those drivers without problem.

else you can buy a better quality boost or buck from DTR or Astralist that he is on the forum.

I still have one of those cheap linear drivers in my stock. It is so old I can't even remember buying it. Most everyone who uses the BDR-209 uses a boost driver and they work very well for this diode. I agree the current was set too high, but I would rethink the entire design of this laser if the OP wants it in a pointer. I would not take a lab host and stick on the end of a battery compartment to turn it into a pointer. Check out the drivers in DTR's website and consider using a nice sized heat sink handheld for the next one.

You mentioned 3D printing the host earlier. Keep in mind that filament has low thermal conductivity so won’t get a long run time unless you incorporate a metal heatsink.

Thanks for all your replies guys!

The heatsink I am using is an aluminum 25mm 12mm bore heatsink with fins which will help with cooling as I can add airflow holes for passive cooling through the fins.

And 550ma or below on the bdr 209, Got it!

And as for the filament. Even with the diode set at 670ma and it getting pretty warm. The heatsink didn't even get close to the PLA melting temp. And there is less thermal contact on this heatsink on the plastic than a solid one would have.

I ordered the driver deadshadow linked me. I don't mind using 2x 18650s to power this. What I meant by "I may build this laser as a portable laser with a DC input" I meant when I finish the host, assuming the driver isn't here yet from china. I will just build a non battery powered lm317 driver to power it externally in replacement of the batteries.

Here is a early print of the top assembly of the host with my....... Dead laser diode.

After finding that I was pushing the diode too hard I am questioning whether to just continue using the 5A CV CC driver. I don't get how if the current is kept within the "safe" zone for the diode why it would not work just as good as a LD driver. I understand that the worry is current spikes on power up and use. Is there a way to test if its suitable for a LD without a oscilloscope? I saw absolutely no fluctuation in beam brightness on power up or use if that determines anything, Actually on power up, I did notice the laser diode seems to almost fade to full brightness like an incandescent bulb. Could this indicate is has soft power up? or is that just the nature of a LD? Also when the diode died, It died in the middle of use and not on powerup. You can also control the voltage and the current independently on this board.

And has anyone here tested one of these boards or the xl4015 ic on an oscilloscope? Here is the datasheet of the main ic, the xl4015 on this board. http://www.xlsemi.com/datasheet/xl4015%20datasheet.pdf

https://i.ebayimg.com/images/g/KswAAOSwXeJYDsIc/s-l1600.jpg"]https://i.ebayimg.com/images/g/KswAAOSwXeJYDsIc/s-l1600.jpg"]https://i.ebayimg.com/images/g/KswAAOSwXeJYDsIc/s-l1600.jpg


Sorry for rambling.

In order for the XL4015 to act as a laser diode driver, it needs to be configured to monitor the current of the diode. Are you sure that photo of what you are using as a driver is not just a voltage converter? I think it is likely so. If so, it should not be used as a driver. If you are using a buck converter that only converts voltage, you will kill the diode as it warms up and the effective resistance of the diode drops. The voltage will remain constant, but because the load is increasing it will draw more and more current casing it get even hotter until it fails.

Here is the description of the XL4015 chip in the datasheet.
http://www.xlsemi.com/datasheet/xl4015%20datasheet.pdf

„ Wide 8V to 36V Input Voltage Range
„ Output Adjustable from 1.25V to 32V
„ Maximum Duty Cycle 100%
„ Minimum Drop Out 0.3V
„ Fixed 180KHz Switching Frequency
„ 5A Constant Output Current Capability
„ Internal Optimize Power MOSFET
„ High efficiency up to 96%
„ Excellent line and load regulation
„ Built in thermal shutdown function
„ Built in current limit function
„ Built in output short protection function
„ Available in TO263-5L package
General Description
The XL4015 is a 180 KHz fixed frequency
PWM buck (step-down) DC/DC converter,
capable of driving a 5A load with high
efficiency, low ripple and excellent line and
load regulation. Requiring a minimum
number of external components, the regulator
is simple to use and include internal
frequency compensation and a
fixed-frequency oscillator.
The PWM control circuit is able to adjust the
duty ratio linearly from 0 to 100%. An over
current protection function is built inside.
When short protection function happens, the
operation frequency will be reduced from
180KHz to 48KHz. An internal compensation
block is built in to minimize external
component count.

That's what I thought. Do not use that to drive a laser diode. It is not meant to do that. The 5 amp current limit is just the most current it can supply safely for an extended period. It will likely have spikes above 5 amps if the device you are driving tries to pull that much. It is configured to be a voltage regulator and that is all. You need a bona fide boost laser diode driver capable of being adjusted to 550 mA.