NDB7875 Run Time

[mhg]

So I purchased a laser with a NDB7875 X-Bucking Driver. 405 G-2 Lense. What kind of run time should I be getting out of that diode? I was told 30 seconds.

 

[marcuspeh]

It depends on the size of the heatsink

 

[Pi R Squared]

So I purchased a laser with a NDB7875 X-Bucking Driver. 405 G-2 Lense. What kind of run time should I be getting out of that diode? I was told 30 seconds.

There is no exact answer to this, it depends on the design of the laser and proper heat sinking and if there were active cooling it could go much longer, but for a typical hand held battery power laser with that diode 30 seconds is probably about right, I have one myself and I consider the duty cycle to be 35 seconds. Overheating it will result in the diode degrading or burning out quickly, if you avoid overheating it can last a lifetime. It may need 1 minute or 1 1/2 minute to cool before turning on again, it depends on the design of your laser.

Alan

 

[mhg]

Thanks. so it sounds about right. will it shut down when over heated ?

 

[Pi R Squared]

Thanks. so it sounds about right. will it shut down when over heated ?

No it won't, there are some drivers that will shut down if they overheat but most do not, and anyway it can't tell if the diode is overheating. In a powerful enough laser both the diode and the driver can overheat. No it won't shut down so be careful, don't make an expensive mistake. Also some of the X-drives flash if the power gets low, so don't panic if your laser starts flashing when you turn it on it just means the batteries need charging, but there are are quite a few different versions of the X-drive if that's what you have. Do you know what current the driver is set at?

Alan

 

[DTR]

Thanks. so it sounds about right. will it shut down when over heated ?

The X-drive will shut down if it overheats but there is no monitor for the diode. The driver unsinked will do 90 on 30 off. As for the diode You will need to maintain a duty cycle based on the heatsink you use.:beer:

 

[TaterMay]

Thanks. so it sounds about right. will it shut down when over heated ?

What heatsink/host is it in? At what current is the diode being run? We can't even give you a ballpark guess only knowing the diode. In my experience with building NDB7875's and actually monitoring the diode temp with a thermocouple and IR thermometer, 30 seconds would be about right if you ran it around its max current and had a fairly small heatsink like a 501B or something. But we really can't help you much without more information.

 

[mhg]

Well I bought this pre-built. I cant find out much on the host. It is the sajme one as the guy in this thread http://laserpointerforums.com/f65/my-new-9mm-445nm-chunk-host-2-4-x-drive-88718.html Could even be the guy I got it from on ebay. who knows. The only difference is the driver board is still enclosed and the entire diode and casing slips into the heatsinc. from what I can tell he has it at 2.3 amps.

Side note if anyone can tell me the type of host this is and a good source for heatsinc upgraded, I would appreciate it.

 

[TaterMay]

Well I bought this pre-built. I cant find out much on the host. It is the sajme one as the guy in this thread http://laserpointerforums.com/f65/my-new-9mm-445nm-chunk-host-2-4-x-drive-88718.html Could even be the guy I got it from on ebay. who knows. The only difference is the driver board is still enclosed and the entire diode and casing slips into the heatsinc. from what I can tell he has it at 2.3 amps.

Side note if anyone can tell me the type of host this is and a good source for heatsinc upgraded, I would appreciate it.

Does your host have any brand names on it? Ultrafire, etc.? Does it also use two 18350 batteries? I have a similar host. I will PM you a picture. If it is the same one, I think I have the same type heatsink at home that I could test for you and give you a decent ballpark guess, though it really depends on whether or not the builder heatsinked everything properly. How long ago did you purchase it?

 

[mhg]

Just got it..."Zero Lasers" exactly like in that thread. ...has two 16340 batteries.

 

[SomeBodyElse]

I have a related question as well, I have been looking at this diode's data sheet and it says absolute maximum rating is 1.7A and not to exceed maximum ratings.

But I also notice DTR sells it with a driver configured for 2.4A

What am I missing? I figured absolute meant absolute, but apparently not if it can be driven at higher amperage than 1.7A.

I figure the answer to my question involves duty cycles and maybe 1.7A is absolute max for a 100% duty cycle?

 

[TaterMay]

I have a related question as well, I have been looking at this diode's data sheet and it says absolute maximum rating is 1.7A and not to exceed maximum ratings.

But I also notice DTR sells it with a driver configured for 2.4A

What am I missing? I figured absolute meant absolute, but apparently not if it can be driven at higher amperage than 1.7A.

I figure the answer to my question involves duty cycles and maybe 1.7A is absolute max for a 100% duty cycle?

I BELIEVE it is both the limited duty cycles and the fact that they are pushed much harder when serving their normal purposes in laser projectors. I believe the main cause of laser diode failure is heat, and that as long as you keep it from overheating, it will live a fairly safe life. The 1.7A current limit is probably to ensure that it could be run at that current for long periods of time without ever reaching a dangerous temp. Of course, even with perfect heat sinking outside of the diode, the wires and/or die inside would eventually reach a current at which they couldn't transfer heat to the case quickly enough. Let me emphasize that this is purely my thoughts on the matter, and hopefully we can get some of the vets in here to comment.

I have built MANY(far too many to keep track of) NDB7875s at 2.4A, and I haven't had a single one die early or be sent back yet.

 

[DTR]

Yep on diodes that are marketed for the projector industry they have a new benchmark of 20K hours of continuous operation compared to 5K so they do need to lower their specs a bit to hit it. Also we do tend to run diodes harder than the manufacturer specifies and specially if going into a handheld even 5K hours is near an eternity for them. If you are putting it in a continuous running application you can think about backing it down a bit but even the projector guys do tend to run them harder as they are fairly cheap diodes and even if they only get a few thousand hours out of them it is a decent trade off for the power to have to replace a diode after that period of time. Anyway all being said yes 2.4A is above the manufacturer rating.:beer:

 

[SomeBodyElse]

Yep on diodes that are marketed for the projector industry they have a new benchmark of 20K hours of continuous operation compared to 5K so they do need to lower their specs a bit to hit it. Also we do tend to run diodes harder than the manufacturer specifies and specially if going into a handheld even 5K hours is near an eternity for them. If you are putting it in a continuous running application you can think about backing it down a bit but even the projector guys do tend to run them harder as they are fairly cheap diodes and even if they only get a few thousand hours out of them it is a decent trade off for the power to have to replace a diode after that period of time. Anyway all being said yes 2.4A is above the manufacturer rating.:beer:

Thanks for the info, question answered! I was under the impression that if I passed an absolute rating the smoke would fly away, and I'm not sure how to put the smoke back in the parts so they work again.