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Problem with Astral SuperDrive and NUBM08

TheAimbrot

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Hey,

I'm having a problem with my Astral SuperDrive and a NUBM08 Diode. I ordered the driver on ebay from barnett_unlimeted. And the Diode from Techhood.

I want to drive the NUBM08 Diode
But I can't get the output current above 1600mA (1.6A). When I turn to potentiometer I can reduce the current. But can't increase it above 1600mA. My input voltage is 8.20V (2x Sanyo 18650 Charged to 4.10V each in series and also tested with Sony VTC4) I measure the output voltage of 6V from the driver. The stated maximum operating voltage of the diode is 4.9v.

I placed a heatsink with a thermal pad on the ic side of the driver as recommended. I had the current meter wired up all the time and the current was never above 1.6A. Also it's strange, that the voltage on the diode is 6 volts. I also tested with a second driver (I ordered two) with same results.

I tested the NUBM08 Diode with my lab bench power supply but at 800mA the Diode draws its maximum Operating voltage 4.9v and above 800mA it exceeds it's maximum Vop. is there something wrong with its forward Voltage ? I really don't have enough experience to say what the problem is.

If there is something important that I didn't mention just ask. Thanks for taking your time to read this. I hope someone could help me.
 



RedCowboy

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Power the driver with your bench supply set to 8 volts and 3 amps and see if you get the 4-4.5a out or 6w+ optical power from your LD because it could be your batteries are sagging below cutoff voltage under load.

Failing that test with an inductive meter how much current your driver is putting into your LD to rule out a defective LD

Make sure your driver is thermally bonded to a good heat sink at the 8 pin chip as they do get very hot and need a heat sink.

---edit---

Sorry I only skimmed through your original post, 6v at the diode is high and using a meter in the output circuit could screw up the drivers output, I only use an inductive meter on the output side of these tiny drivers, you can use your meter inline on the input side to see what it's drawing but adding any resistance on the output side can change the drivers output, just making your wires a few inches long between the driver and diode can lower the output to the diode.

The max output of that driver is 5a and the NUBM08 will stand 5a for a while in my experience, have you tried to connect the driver to the diode without your meter in the circuit ?
My bet is your meter and additional connecting wire added between the driver-diode is causing the problem.
 
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TheAimbrot

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Power the driver with your bench supply set to 8 volts and 3 amps and see if you get the 4-4.5a out or 6w+ optical power from your LD because it could be your batteries are sagging below cutoff voltage under load.

Failing that test with an inductive meter how much current your driver is putting into your LD to rule out a defective LD

Make sure your driver is thermally bonded to a good heat sink at the 8 pin chip as they do get very hot and need a heat sink.

---edit---

Sorry I only skimmed through your original post, 6v at the diode is high and using a meter in the output circuit could screw up the drivers output, I only use an inductive meter on the output side of these tiny drivers, you can use your meter inline on the input side to see what it's drawing but adding any resistance on the output side can change the drivers output, just making your wires a few inches long between the driver and diode can lower the output to the diode.

The max output of that driver is 5a and the NUBM08 will stand 5a for a while in my experience, have you tried to connect the driver to the diode without your meter in the circuit ?
My bet is your meter and additional connecting wire added between the driver-diode is causing the problem.
Ok, well after thinking about that it does make sense. Yes I have a bit longer cables at the output and also the power meter in series to the diode and well it's an resistive load. Makes sense that this could make the driver function incorrectly.

Ok so I will put the power meter at the input side to at least have somewhat an idea of how much current goes to the driver/diode. But the voltage I'm obviously measuring parallel to the diode at the output of the driver shouldn't be a problem right ?

Which conductive power meter are you using ? I saw some cheap ones on eBay but how good/accurate are these. I only have a big clamp meter that wouldn't work...

Thanks for your reply/idea. I will test it as soon as I have time ( in about 2 days sadly :/ ) and will respond with the results.
 

TheAimbrot

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Hey,

So today I tested the Diode with the Driver again and changed two things. First I shortend the wires from the Driver output to the Diode and directly connected them (without a amp meter in series or volt meter parallel) I put the amp meter in series of the Driver input and the battery's to measure the input current but it sadly never drew over 1.6A so I'm pretty sure now the Diode is defective. Can I test something else ?

I'm thinking about sending the Diode back if the seller accepts. But in the other hand I pretty sure somehow the diode has an output power of over 2W compared to my pltb450b diode with 1.5W but scince I don't have a laser power meter I can't really tell.

I bought it for 23€ and don't know if it's really worth it

So if someone can tell if the Diode is broken or has another idea I'm happy to hear your suggestions. Thanks
 

paul1598419

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It is unlikely the diode's seller will take it back after you connected it to a a driver that is not known to be working. Laser diodes are consumable items and if there are possible problems with it you should try to ascertain that the diode is working before you connect it to an unknown driver. You can try, but don't be surprised if they won't accept it back.
 

RedCowboy

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Had you powered the diode with your bench top power supply ?

For a NUBM08 I usually limit my voltage to 4.7 driving a short then turn the current knob all the way down and connect my diode ( in a heat sink ) and slowly turn up the current to 4.5a, before I can reach 4.5a I will have to bump the voltage up a little, of course you back the current knob down to where it's in regulation at your 4.7v then bump the voltage so you don't overshoot, the diode should take 4.5a without dimming down.

If it starts to dim down then back off the current right away, these NUBM diodes are pretty tough and can usually take a quick small overcurrent but you don't need to go to 5+ amps looking for the fold back, rather just see if it will take 4.5a or if it dims down sooner and at what current, you could have received a weak/wrong diode or you may have damaged it as your driver could be defective as well, have you tested the driver driving a big 1 ohm resistor or a resistor and rectifier bank dummy load ?
 
Last edited:

0C_Monk3y

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It should pull as much amps as you cram it with, mine was pulling 4000 mA (DC clamp meter). I unfortunately just fried my new NUBM08 last night, although I have no idea how because it worked great for like 15 seconds in total until it turned into a weak LED, lol! Hopefully you solved your problem, if not, maybe this will help someone in the future looking through these comments, I'd recommend checking your driver side, wouldn't surprise me if a Chinese driver took some marketing liberty with its power claims. Good luck!
 

hakzaw1

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They say--if you fail and then try again using the same 'everything' expect another fail. There are prolly a dozen ways to make a laser diode into a weak LED.
No part of ESD precautions should be ignored.
ALL Caps need to be shorted out before connecting to a diode.
Some say a workbench PS may not be a good idea.
NO diode should be powered up if it is NOT in a proper heat sink.

AND the cheaper china drivers were made to power LEDs not laser diodes.
The drivers from Pradipta (Astrailist) are good.
Always use ESD wrist strap, rubber gloves or work mat.
AND of course never power a diode directly from any battery, even for just one second.
MYB you can get with another member and get 'hands-on' help (the best!!)

PM me anytime if I can help---hak in TEXAS.

ps
Due to all the above and other end-user 'mistakes' laser diodes are not warranted very often.
no returns no free diode or driver.
 

paul1598419

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I have powered diodes without heat sinks just to measure the wavelength. When doing this, I only take the diode just above threshold. It only takes a couple of seconds to do one once you get it all set up. Now, I have heat sinks that don't need to be pressed, but that does take longer to bin diodes when you have many to do.
 

hakzaw1

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I get what you are saying Paul... you have LOTS of experience going for you. I tend to err on the side of safety when the person has less experience.
If one second is harmless.. how about 5 seconds?... for them using a heat sink IMO is a good idea.

Very few here have ever binned diodes.k

ha
 

paul1598419

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Yeah, I have done this with many, many diodes. I do know what I'm doing, so if you don't......don't try it.
 

RedCowboy

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I have powered diodes without heat sinks just to measure the wavelength. When doing this, I only take the diode just above threshold. It only takes a couple of seconds to do one once you get it all set up. Now, I have heat sinks that don't need to be pressed, but that does take longer to bin diodes when you have many to do.
But the wavelength can vary by some amount with temperature and current so shouldn't you heat sink the diode and drive it at the normal operating current and temp ?
Seems like sticking a naked diode is a socket is a bit lazy and testing for wavelength at low power may not yield a true representation of what the end user will obtain.
 

paul1598419

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These diodes were not made to be driven the way we do here. That said, they tend to shift wavelength more with temperature than current. Driving them just above threshold gives an accurate representation of their wavelength and, in the time it takes, does not increase their temperature enough to cause a shift. I have done many dozens of wavelength bins like this. If you wish to know what wavelength it is after you over drive it in a heat sink you should measure it again at that time.
 




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