How to drive 60W laser array, and make dummy load.

[lostbeam488]

I got my hands on a 60W OSRAM 450nm laser diode array. The package has 4 channels, each with 5 diodes in series. The operating current of each channel is 2A. What's the easiest way to power this? Is there any good constant current drivers that can output 100V+ at 2A? Or would it be easier to use 2 or 4 separate drivers? Also, what kind of diodes would I be able to use as a dummy load to test the driver current?

 

[RedCowboy]

I've been using an LM338 configured as a current regulator with all the all the channels wired in series.

 

[lostbeam488]

I've been using an LM338 configured as a current regulator with all the all the channels wired in series.

I thought the lm338 could only output 32V? Wouldn’t that only be enough to power one channel?

 

[RedCowboy]

That's as a voltage regulator, configured as a current regulator there's not a voltage limit within physical reason, 100V should be no problem, but you can use one for each channel if it makes you feel better.

I'm using an LM338 with 16 x 18650 ( about 65V ) to drive two strings of seven ( 14 lasers ) in a nubm35 array, my resistors are 3 x 1ohm in parallel for 0.33 ohms giving me about 3.65A.........actually the array draws about 58V but you need to allow for dropout and battery sag.

 

[AnselmoFanZero]

I bought the 48W version from techhood and their driver is acting weird. Did you just buy the array without anything else?

 

[RedCowboy]

Yes I just buy the arrays and make my own drivers or buy a dc to dc.

These have been working for myself and others, you would want 2 of them so you can use one driver for each 12 laser diodes ( 2 strings of 6 in series ) or you can use the larger one I linked to you in another thread that's good for 120v and drive all 4 rows of 6 in series ( 24 laser diodes )

NOTE: You need to heat sink the dc to dc and your laser array to dissipate waste heat.

p.s. I have bought the Osram and some of the N1ch1as and the Osram is junk, the alignment and focus is poor compared to the N1ch1as.

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[AnselmoFanZero]

I am not the electronics guy but I know lasers are a bit sensitive when it comes to current and voltage...mor towards voltage though.
Techhood doesn't even tell you the voltage output I think. I bought a package and now Im screwed.
Was it 3.5V per diode @1.8A?

 

[RedCowboy]

The Osram uses smaller diodes than the N1chias, the Osram diodes need about 1.8A @ 5V each so to power all 24 laser diodes you need about 120V @ 1.8A

The N1ch1a laser arrays need about 3.5A @ 4.5V each laser diode. So a NUBM31 with 20 laser diodes ( 4 rows of 5 each ) needs about 90V @ 3.5A

The driver techhood sells may not work to power all 24 of your Osram diodes, you could try powering just 3 rows and see if it works, you would need 90V @ 1.8A

So turn the pot on your driver all the way down then connect it and turn it up slowly with a volt meter connected in parallel or I like to use an inductive anameter to see the current.

 

[AnselmoFanZero]

Oh so 5V...damn. I have added an amp-meter, shows me 20mA....which should be the current for the green status LED on that techhood PSU -.-
I got a regulated powersupply....should work if I set it to 120V/1.6A right?

 

[RedCowboy]

If you have a bench top power supply start low and turn it up slowly keeping the current and voltage in regulation.

Laser diodes don't like spikes.

The dc to dc I linked above can be adjusted to the current and voltage you want then switched on and off, others have been using the same as well. You will need 2 of them, one for each string of 12 laser diodes. ( 2 rows in series )

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[AnselmoFanZero]

Yeah thats what I meant earlier. One spike and you have wasted a few $.
Would be easier to power all rows from one....but all I can find are 900W versions. Thats a bit much. Bet they are alot bigger than what I would need to run the laser.

 

[RedCowboy]

900W just means they can output up to 900W if needed, they can supply 1.8A @ 60V to power 12 laser diodes which is only 108W but you need 120V to power all 24 laser diodes, so it's not the wattage but the output voltage which you need 2 drivers for your array.

I like to use an inductive meter to set my current limit.

If you get an inductive meter make sure it can read DC amps as well as AC amps.

 

[AnselmoFanZero]

Oh I know, I am just assuming its way bigger than needed.....AxBxH.

 

[mike genericlastname]

Hey I'm about to start running an 60w osram 450, I would love to know how that turned out for you.
I usually run a single diode instead of an array, they look steampunk but they work great mobile.

 

[RedCowboy]

These work very well, make sure to read the directions. 8 - 60VDC input and 10 - 120VDC output dc to dc boost power supply, so you can run your entire array in series @ 2A

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[mike genericlastname]

Yeah, I'm running one of these that should make it work. Don't laugh, one of the goals is to make this almost entirely out of recycled materials. Almost.
I was actually intending on combining it with a few nubb24. But I appreciate the experienced parameters when it comes to voltage for the osram array. I hadn't realized when I was buying it that it was a four channel system. Thank you again.