Pulse driven NUBM44 ?

[paul1598419]

If you are talking about the LPC-816, 826, 836, 840, then yes they do claim that. But, we typically drive them CW 300 mW to 400 mW. Since we are over driving these to their limit already, I don't see you getting more out by pulsing them.

 

[logsquared]

I have done some research and experimenting on pulsed diodes. I have pulsed a m140 diode at 10amps 10% duty cycle. The optical power output was only slightly less than running the same diode at 1amp continuous. I imagine the difference was due to increased VF from the die attachment wires. Or possible because my wave train wasn't perfect.

From what I have read, the output peak power is limited by the facet and by the die attachment wires. There are some other things that determine long term degradation like ion migration.

Because the facet of the blue diodes is relatively large huge peaks should be possible. The CW rating is basically the point where the amount of waste heat can be removed without damage. So, In theory as long as the average power is maintained and the facet remains intact the diode should live. However, it should be noted, too low a frequency will kill the diode because the heat can't be moved from the die fast enough between pulses. Pulse freq. is something that would have to be tested as the diodes are not characterized for pulsed by the manufacture.

I have no doubt the 44 diode will almost double its power pulsed at 50% with 2x the current.

The downside is the eye tends to average the power just like a LPM. So, unfortunately the laser will probably look the same brightness. There is some debate to this in the science community. Recent studies have shown that pulsed light can appear brighter than CW but only for very short duty cycle (10% or so) and its only a few percent brighter. This is very hard to test because it takes aprox 2X the optical power for the eye to perceive a change in brightness. And this is dependent on several other factors as well.

At $127 its tempting to buy one to test out.

 

[Encap]

RCB: Are you sure that claimed "15W" unit is not 2 diodes combined.

OPTlaser make a 12W 445nm engraving head using 2 nubm44s although it is a lot more expensive see: https://optlasers.com/en/34-engraving-laser-heads

 

[Benm]

Pulse driving lasers is only useful if you are limited by certain factors, such as:

- speed at which you can send pump energy in
- thermal limitations causing overheating but no other problems

The issue with high power diode lasers is that these often are not the main limiting factors as long as you provide enough heatsinking. One limitation is in the optics, which still suffer damage if you run it at high output power even at a limited duty cycle.

You cannot, for example, take a 1-watt-continous rated laser diode + heatsink and just run that at 100 watts with a 1% duty cycle. The heatsinking will still be adequate (provided you do this modulation at a reasonable frequency), but it will destroy the optical facets and such: there is a thermal factor in that, but also a factor that depends on sheer power density.

Compare it to how much force is excreted onto a window when leaning against it for a minute (or hour, or the rest of your life) versus shooting it with a handgun. With the moderate force of leaning it will never break regardless how long you keep that up, while the gunshot will shatter it in milliseconds.

 

[lasersbee]

RCB: Are you sure that claimed "15W" unit is not 2 diodes combined.

OPTlaser make a 12W 445nm engraving head using 2 nubm44s although it is a lot more expensive see: https://optlasers.com/en/34-engraving-laser-heads

I'll let you know when it shows up.
I ordered one yesterday to to some Shop
Thermopile testing....

BTW... I don't think they would be driving
2 LDs in parrallel from one driver. I could
be wrong.

Jerry

 

[Benm]

I would not be overly surprised if they ran two LDs in parallel from a single driver.

From a best practice electronics standpoint doing that would definitely be out of the question, since the one getting warmer gets a lower forward voltage for a given current and this seems to be a serious risk of thermal runaway frying the hot diode first, and the other one after if the first fails open circuit.

Then again you also see LED strings where they run 100 of them in parallel, and those tend to work just fine, despite being a stupendous mistake from an electronical design standpoint.

 

[logsquared]

I would not be overly surprised if they ran two LDs in parallel from a single driver.

From a best practice electronics standpoint doing that would definitely be out of the question, since the one getting warmer gets a lower forward voltage for a given current and this seems to be a serious risk of thermal runaway frying the hot diode first, and the other one after if the first fails open circuit.

Then again you also see LED strings where they run 100 of them in parallel, and those tend to work just fine, despite being a stupendous mistake from an electronical design standpoint.

I doubt the laser module RC has posted has two laser diodes in it. First, the extrusion the module is made from would be difficult to house two combined diodes. Also, the lack of any adjustments to overlap the beams would make it mostly useless.

Second, it seems if it had 2 7-8W diodes they would rate it at 14-16W CW.



All the led strips/ strings i've seen have a current limiting resistor for each led. So, not a problem electrically.

 

[lasersbee]

I doubt the laser module RC has posted has two laser diodes in it. First, the extrusion the module is made from would be difficult to house two combined diodes. Also, the lack of any adjustments to overlap the beams would make it mostly useless.

Second, it seems if it had 2 7-8W diodes they would rate it at 14-16W CW.

All the led strips/ strings i've seen have a current limiting resistor for each led. So, not a problem electrically.

That is the main reason I think it's a
single LD. There is not much room in
those extruded housings.

Jerry

 

[Benm]

All the led strips/ strings i've seen have a current limiting resistor for each led. So, not a problem electrically.

On the good ones there would be, but i have some led xmas lights that run 50 leds just wired in parallel with a single resistor to limit the current for the whole lot. This is a very cheap item though, but it does work without much of a problem, though if you look closely you can see the led's on the far end of the string are slightly dimmer due to the resistance of the wire.

Then again i hope people are not that careless with more expensive components. It's also notable that those led's are ran at a fraction of their maximum current (under 1 mA each when they could handle 10 mA easily, but i guess that's to make the batteries last longer).

 

[lasersbee]

Heads Up.....

I haven't received my 15W Laser yet but
one of our nearby customers contacted us
to ask if we could measure a 15 Watt Laser
for him. He has a 5.2W LaserBee AX3.

Seems he bought the exact 15W Laser we
bought on eBay and from the same seller but
he can't measure it properly on his LPM.
He is supposed to come by the shop this
morning. I'm curious as to the actual output
of this "15W" laser and if it has 2 LDs in it.
https://www.ebay.com/itm/15W-Laser-Head-Engraving-Module-450nm-Blu-ray-w-TTL-Wood-Marking-Cutting-Tool/372165311401?epid=3011321747&hash=item56a6c7fba9:gswAAOSws6ZaMNPe

I'll post the results when he gets here and the
power tests are done...


Jerry

 

[lasersbee]

The Guy finally showed up at 2:00 PM.
His 15W Laser was exactly the the same
one I ordered...

I needed to run a +5V supply from the
Driver board to the TTL input pin to test
the Full Power of this 15 Watt Chinese
Laser....

Hope no one else bought one of these...
Only one LD inside and a whopping 4.6W
output.
If mine is as low powered as this one I'll be
opening a PP dispute.


Jerry

 

[paul1598419]

I also doubt the 15 watt claim made by this seller. I will be looking forward to some actual figures on these.

That's what I figured.

 

[DTR]

I posted some testing on these a while back by one of my engraving company customers. The unit tested had a NUB units with the ball lens removed. He got a little more power out of that one though and it was called a 12W unit.

https://laserpointerforums.com/f65/nubm44-6w-450nm-laser-diode-94119-44.html#post1480862


They will never use NUBM44 diodes when they source the NUBM08/41/05/06 ect.... so cheap and they just started getting their hands them recently as pulls from used machines.

I get people asking about replacing diodes in those things quite often as they either arrived DOA/LED or went LED within a very short period of time.

 

[RedCowboy]

Taking a reading with a thermopile you wouldn't know if you had half duty cycle 15w pulses or 7.5w CW, just the average power of 7.5 or 5.4 whatever the number, I wonder if they are actually pulsing the diode albeit a doomed de-canned likely used pull at a higher peak power for short pulse widths of any percentage, I suppose I would need a photocell capable of withstanding the pulses to get a real time peak pulse power reading, not that these are even worth having, what I am thinking about is the possibility of pulsing a LD at higher power for short on time pulses, someone said no yet Alaskan was wanting to do just that with an IR diode, maybe with active cooling it would be possible.

Of course I wouldn't expect to get a million watt spike for a billionth of a second, but maybe a nubm44 diode good for 7w CW could put out 20w pulses at 10000 cycles a second with an ON duration of 10% the pulse width, I get it that the average power would be around 2w but the peak intensity could be 20w pulses, and would that result in an increased ability to do work ?

---edit---

It should look a lot brighter to our eye if possible to do with our MM diodes, even if doing useful work was not in the realm of possibility at the aforementioned level.

 

[DTR]

Yea here is the guy that post was for taking a look inside his 15W unit to see if it could be replaced with a NUBM44. Jerry can you confirm that units also has a NUB decanned ball lens diode. It might have the lens glued in place so you can't peek in there.

Is it possible to determine from this photo what laser diode is installed? Module purchased here https://www.aliexpress.com/item/Fre...-Blue-Light-450nm-laser-head/32750454123.html Module worked very little, very quickly degraded.Perhaps this photo will help to accurately identify. Tell me whether it can be replaced by NUMB44. How long the NUMB44 will work?

 

[lasersbee]

Taking a reading with a thermopile you wouldn't know if you had half duty cycle 15w pulses or 7.5w CW, just the average power of 7.5 or 5.4 whatever the number, I wonder if they are actually pulsing the diode albeit a doomed de-canned likely used pull at a higher peak power for short pulse widths of any percentage, I suppose I would need a photocell capable of withstanding the pulses to get a real time peak pulse power reading, not that these are even worth having, what I am thinking about is the possibility of pulsing a LD at higher power for short on time pulses, someone said no yet Alaskan was wanting to do just that with an IR diode, maybe with active cooling it would be possible.

Of course I wouldn't expect to get a million watt spike for a billionth of a second, but maybe a nubm44 diode good for 7w CW could put out 20w pulses at 10000 cycles a second with an ON duration of 10% the pulse width, I get it that the average power would be around 2w but the peak intensity could be 20w pulses, and would that result in an increased ability to do work ?

---edit---

It should look a lot brighter to our eye if possible to do with our MM diodes, even if doing useful work was not in the realm of possibility at the aforementioned level.

The 4.6w output was not pulsed. I quickly scanned
the beam across a white wall and it was a solid line.
As I mentioned above I put +5VDC on the TTL input.

Yea here is the guy that post was for taking a look inside his 15W unit to see if it could be replaced with a NUBM44. Jerry can you confirm that units also has a NUB decanned ball lens diode. It might have the lens glued in place so you can't peek in there.

I had removed the Lens to see if I could see some
optics to combine 2 LDs but all I saw was similar to
the picture you posted. No Gball lens. It did have
clear window between the LD and copper lens holder.
I took a pic but I don't have a macro lens and you
really can't see the clear lens.

Jerry