Which bench power supply are you using to test diodes?

[T_Warne]

I recently returned to the hobby and I have a ton of un-labled mystery diodes that I want to test. I'd love to know what bench supply you are using to test your diodes. Or perhaps you can suggest a good entry level power supply in the $100-ish range ?



Of course... if you have a link to one, I'd be this happy.

thanks! :beer:

 

[RedCowboy]

 

[T_Warne]

That looks like it takes up a lot of space. I dont think it will fit on my workbench.

 

[diachi]

I've got a Korad KA3005D that I'm pretty happy with. Haven't run any diodes with it yet but the output looked nice and clean on the scope.

 

[RedCowboy]

I have this one on my bench in this room, I have many others, but this one has worked well.

It's best to know your diodes specs before powering it this way, of course you want your diode in a heat sink.

I have been using these for years and know what I'm doing, if you don't you can easily blow your diode.

https://www.ebay.com/itm/DC-Power-S...281968&hash=item3f66d798fb:g:IHYAAOSwrhBZCZU5

 

[paul1598419]

That's not a bad supply, but it is overpriced by $10.00. I don't happen to have the link handy, but it can be found on eBay. For most diodes, it is better to have the 30 volt 5 amp one as it has a low and high current switch that the 10 amp one doesn't. It is also less expensive.

If you haven't used a CV/CC power supply to drive a laser diode before, it is good advise to learn, or you will lose a lot of diodes.

 

[lasersbee]

I recently returned to the hobby and I have a ton of un-labled mystery diodes that I want to test. I'd love to know what bench supply you are using to test your diodes. Or perhaps you can suggest a good entry level power supply in the $100-ish range ?

Of course... if you have a link to one, I'd be this happy.

thanks! :beer:

I used to use a Shop built PS for Laser Diode
testing until I found this one. Good to 5 Amps.
There are other models available. Quite precise
with minimum current increments of 1mA.

https://laserpointerforums.com/f67/affordable-adjustable-lab-laser-diode-power-supply-101936.html

Jerry

 

[Alaskan]

I've burned out a few diodes using a cheap Chinese 3 amp CC adjustable power supply, my error though. Don't turn on the power supply with the diode connected, they only regulate the voltage and current after awhile, too long for the diode, pop! Have a momentary power fluctuation and again, pop!

 

[lasersbee]

I've burned out a few diodes using a cheap Chinese 3 amp CC adjustable power supply, my error though. Don't turn on the power supply with the diode connected, they only regulate the voltage and current after awhile, too long for the diode, pop! Have a momentary power fluctuation and again, pop!

I agree 100%.. I found the same problems
until I found and tested the Digital Power
Supply in that linked Thread.

Jerry

 

[RedCowboy]

A load has resistance, for instance only 1 amp per volt will flow through a 1 ohm load, so if I connect my 30v 10a PS to a 1 ohm load and turn the pots up it will show 10a and 10v but knock a wire loose and the voltage will jump to 30v as the output filter caps charge, reconnect and POW you blow your load.....I know that sounds funny........

Laser diodes can change resistance as they warm up, so if you start at threshold voltage established by setting up with the PS driving a short and your current turned back all the way down, you want to chase your current behind your voltage making small increases until your current is in regulation where you want it, you also should turn back your voltage until you see the current start to drop so that both are limited.

If you are running with your CC light indicating that your current is in regulation your voltage could still be turned up past what it needs, but because the current is limited only so much voltage is flowing due to your loads resistance until you knock a wire loose, then your output caps charge and when you reconnect POW. Don't do this, if a wire comes loose turn it down and start over.

Buy a PS with a low ripple/noise and good voltage/current/load stabilization to start with, but you still need to know how these crude supplies work and safeguard your diode with the proper procedure, such as turning all pots all the way down and turn your PS on unconnected, then set your threshold voltage by driving a short and start with your current turned back down, then connect observing polarity and chase your small voltage increases with current increases until your current is in regulation where you want it and back your voltage down so it is also limited, but as the diodes resistance can change with heat these power supplies are ok for testing but not meant for unattended driving and you must follow procedure each time or you can easily blow your laser diode.

Using a PS like this to hunt through unknown diodes is not recommended unless you know what you are doing, and even then you can blow them easily.

This is not a full tutorial, just a brief insight, so use at your own risk.

p.s As Alaskan said, never start with your load connected and your PS turned off, you will blow diodes, establish a max voltage driving it shorted to meet your diodes threshold, and then back your current down before connecting your load, then increase current slowly until you see it wont take any more at that limited voltage, then slowly chase current increases behind voltage increases, in effect you are part of the regulation as resistance can change and crude power supplies are not meant to be drivers on their own, and even when your current and voltage are both limited you can not switch your diode on/off with the PS switch, always turn the current and voltage back down to zero before you disconnect then follow procedure when testing the diode again, do not switch with the PS, they can and will spike and POP your diodes.

 

[T_Warne]

Thanks for the suggestions and guidance. As I stated, I will be testing diodes that I no longer remember the identification of. I'm willing to take the risk of blowing a few up in the name of discovery. I consider this a learning exercise. ( plus, it's a great excuse to buy a new tool )
Consolidating the suggestions:
~ Gilligan's Island human powered generator
~ KORAD KA3005D - Precision Variable Adjustable 30V, 5A DC Linear Power Supply
~ Costway 30V 10A 110V Precision Variable Digital Power Supply
~ Costway 30V 5A 110V Precision Variable DC Digital Power Supply
~ RD DPH3205 Buck-boost converter + Power Supply Housing + it still requires a power source

In another power supply thread I saw the mention of using a transistor socket so you don't have to solder and un-solder every diode. I'll be testing 3.8, 5.6, and 9mm diodes. I found these at Thor labs, but they want $9.73 just to ship the set of 3 holders. :scowl:

 

[RedCowboy]

The power supply I bought came with clip leads, it's easy enough to clip to the diode pins, but you need to know polarity.

You could start by metering the resistance especially of the diodes with case pins to see if they are case neutral or not, some may have a photo diode included.

I suppose you could start at 2 volts driving a short then connect to a diode and increase current from nil, then turn the current all the way down and disconnect and set to 3 volts driving a short then connect and increase current, and so on....but the IR diodes you won't see working so I would use a security camera as they don't have the IR blocking filter.

You do want to protect your eyes of course and the diodes need to be in a holder/heat sink, plus you will be looking for the point where the diodes start tapering off so you pretty much need a laser power meter.....also looking at the diodes markings could allow you to make an educated guess on some of them, maybe someone who's done this could make some suggestions, do you have any idea of what they come from, are they used or new ? Most of all protect your eyes.

 

[paul1598419]

I use a transistor socket with short wires soldered to the pins. I then connect the laser diode to the socket and after turning on the PS and setting the voltage and current to 0, I short the leads before connecting to my socket. This works well for me and have not lost a diode in testing yet.

 

[RedCowboy]

No heat sink ? You must just make a quick function test, for finding the diodes fold back you would have it in a heat sink I'm sure, for a function test of the static protected blues I just use a lithium button cell pinched between the pins observing polarity of course.

 

[T_Warne]

@ RedCowboy
I have glasses for red, blue, and IR. I have a Laserbee. I have the old Meredith module that makes it easy to test 5.6mm and 9mm, as well as different lenses.

Most of my diodes are from back in that days if sled harvesting and group buys. I was never really into the reds, so I'm fairly certain they will mostly be 405nm. Although, the one I am most curious about is a 3.8mm pressed into a module. From the look of the pins, it was soldered to a driver at one point. The glass lens has red ar coating. My best guess it PL450, as that was the last type of diode I bought before I stopped building.

I'm fairly certain this is a NDB7875

I think this one is out of a blue ray sled, but I cant remember if it is 405nm, or red/IR. A google image search returned a bunch of glass junk.

The IR stuff is easy... it's all 9mm.