DPS 5020 as Fiber laser diode power supply - Page 1
Forum section: electronics / projects

author: MDM3D
author_rank: Contributor
timestamp: March 26, 2019, 05:21:21 pm
content: Hello EEVBlog Forum users, I have stumbled upon an ebay listing for a bunch of IPG PLD-30-974 30W fiber laser diodes. I know little about the power supply requirements of driving a laser diode other than that they are "sensitive" to over voltage and over current and that dedicated laser driver power supplies are expensive. I have played around with the ruideng DPS 5020 power supply modules before and based on my limited knowledge they seem to fit the bill for this Laser diode. they can alsy be controlled with a pc or micro easily. I have read a few other posts on the forum that recommend a fixed voltage supply with current limiting resistors and a low side switch but that seems a little too crude as compared to the dps 5020 offerings. Please advise if I should jump off this crazy train. I have done a fair bit of research on the various lasers themselves and will be purchasing all of the safety equipment/enclosures/interlocks. Currently I am just trying to figure out a cheap way of powering this laser for use in a (to be built) laser cutter.

author: Benta
author_rank: Super Contributor
timestamp: March 26, 2019, 05:30:46 pm
content: Power laser diodes have a built-in photodiode for feedback. This should not be ignored and be used for controlling the laser driver. A simple power supply and limiting resistor will not do the trick.

author: MDM3D
author_rank: Contributor
timestamp: March 26, 2019, 06:15:48 pm
content: This particular device has only 2 leads and as far as I can tell does not have a photo diode.

author: ajb
author_rank: Super Contributor
timestamp: March 26, 2019, 06:39:38 pm
content: Constant voltage and a resistor is actually okay for low power, low precision testing (IE, 'is it dead?'), in fact it's a better bet than using a typical bench supply in CC mode with no resistor (best method is a bench supply in CC/CV mode, with appropriate current voltage limits set, *and* a resistor). Copackaged photodiodes are not actually all that common among commodity diode lasers. You still see them in OPSL heads and scientific modules, but these are not actually part of the laser diode itself but fitted somewhere else in the optical assembly.Diode driver requirements really depend on the application, but as a rule they should be designed as current sources first, above all else. Without knowing what the topology of the DPS 5020 is like it's impossible to say how good of a laser diode driver it would be. A basic linear constant current driver is pretty simple as long as you're not too concerned with efficiency, high modulation rates, or super high stability (in which case you really want a photodiode). Anything used for experimentation should also have saturation detection to disable the power stage when the diode is disconnected, otherwise the diode will get a nasty wallop if it gets connected with the driver enabled.What are you looking to do with the diode?

author: MDM3D
author_rank: Contributor
timestamp: March 26, 2019, 06:49:34 pm
content: AJB, the DPS5020 is a Buck converter SMPS module low side switched. I would be using this laser to cut plastic, wood, ablate paint off of copper PCB's for etching and do basic metal marking.please see the link below for a DPS 5020 overviewhttps://www.eevblog.com/forum/testgear/testreview-of-power-supply-frontend-dps5015-50v15a/The DPS5020 is a larger supply of the same topology as the DPS5015.below is a link to the laser diode's datasheethttps://www.ipgphotonics.com/en/641/Widget/PLD-40+Laser+Diode+Datasheet.pdf

author: ajb
author_rank: Super Contributor
timestamp: March 26, 2019, 06:57:38 pm
content: Yes, the DPS power supplies are well known, but you would need to examine its exact topology and the type of control scheme used to be able to tell if it's likely to make a good laser diode driver. I didn't find any schematics for it in ~5 seconds of googling, but if you link them you may get better answers.Note that that datasheet is for the ~40W version of the diode, so the actual power/current ratings for yours will be ~75% of that. Also note that the operating current rating is the same as the maximum current rating. Getting peak performance out of laser diodes leaves very little margin for error! So don't even try to push it to its limits until you have firmly established that your driver is sufficiently stable.

author: Benta
author_rank: Super Contributor
timestamp: March 26, 2019, 07:19:00 pm
content: Just to correct my own misunderstanding and that from others as well:The PLD-30-974 is NOT a "laser diode", but a "diode laser", meaning a complete module with laser power control. Precise terminology is nicer...

author: ajb
author_rank: Super Contributor
timestamp: March 26, 2019, 07:33:00 pm
content: Quote from: Benta on March 26, 2019, 07:19:00 pm"Diode laser" vs "Laser diode" isn't really a concrete distinction. A laser diode is, optically, an entire laser in a sliver of semiconductor, so calling it a 'diode laser' makes perfect sense. An assembly that includes a laser diode and driving electronics might be called a diode laser module. In any case, I see nothing to indicate that the parts in question contain driving electronics--if they did, that would generally be advertised in the datasheet and it would have more than two pins. (You do occasionally see transient suppression or reverse polarity protection devices integrated onto the laser die, but that's about it, as the driving electronics tend to be highly application-specific.)

author: LaserSteve
author_rank: Super Contributor
timestamp: March 27, 2019, 12:21:31 am
content: Jump off the train. These things are dangerous. They also probably have a gazillion hours of operation on them which makes them electrically brittle, and sensitive about their age.One of the things I often see on EEVBLOG is that laser diodes are described as glorified LEDs that can be ran off a current limiting resisitor. The issue with this is they are amazingly sensitive to short spikes that will not harm a LED, but will blow the reflecting faucets off the ends of a laser diode chip and turn them into lousy damaged leds... Those of us who use these for our day job go out of our way to drive them from pure current sources with soft starts, voltage clamps, protective limit circuits, and careful arangements to close the current control loops before applying any energy to the diode itself.If I had a dollar for every LD I've seen or heard of a bench supply blowing, I'd have enough money to fly to Straya, meet Dave and marry a good looking Aussie chick. Especially the supplies with tap changing relays in them or little 20 to 200 uF caps across the output terminals at all times.. If it comes up in an undefined state, it is NOT an LD driver..First thing, get a Lasorb across the laser diode.www.lasorb.comThis protects it against spikes. I know its a huge LD chip and you would think that a burst of static will not kill it... Wrong.You have a fiber coupled laser diode. We refer to the 974 nm wavelength laser diode as "PUMP" diodes. IPG uses them in their lasers to pump a lasing fiber that lases at a different, longer wavelength. Basically store the energy as an upper energy level in a dopant metal ion in the fiber, for about 250 some microseconds, then dump it out in a few 10s of nanoseconds. So you have the continuous Pump Laser for a Pulsed Fiber Laser that uses Q-Switching, which you can think of as a form of pulse compression of sorts, the optical equvalent of dumping out a capacitor. So a typical IPG laser would have many modules like yours pumping a long fiber laser, and a Q-switch module to block the fiber laser from lasing until enough energy is stored in it to dump a pulse. The high peak power in a short duration is what is useful, and at these wavelengths, quite scary.Now for the worrisome part on my end.. Please buy a quality pair of Laser Safety Goggles for yourself and anyone else who may be in the room. Including your wife, children, coworkers, friends, garbageman, dogs and cats..https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=762You need a certified goggle, not a untested, uncertified 50$ Chinese clone goggle from Ebay or Amazon.. Preferably OPTICAL DENSITY SIX OR GREATER!Then find a nice black and white CCD camera and remove the IR filter on it and use it for alignment, etc.. 974 is down at the far end where silicon and CMOS have a still useful but very weak response. Back reflections, even weak ones, will easily fry pixels in the camera/lens combination.. Trust me on that, too...Even if you totally enclose everything, you want the goggles.. Trust me on that...Make me happy and toss that thing in the trash...Even diffuse and specular reflections from that diode can be a hazard. When is laser light not a hazard? Well only when totally contained and when the scattered light has been profiled, measured, documented and checked against the rules, and when the design is checked by another laser safety professional.That 970 nm wavelength likes to go through skin until it finds nerves, blood vessels, bone, immune system or muscle tissue, and then it it frys it. It is also an excellent eye hazard...You only see IR TWICE...It also has a habit of damaging your peripheral vision without you noticing it, well, until the truck hits you...Next up, when the seller removed those things from the fiber laser, he roughly cleaved the fiber, but did not polish it. This means you now have a laser diode that may have a distorted output when collimated. Usually we cleave them at an angle to prevent back reflections into the diode and then polish the end. So you have NO idea how that beam is exiting the fiber, or where it exits the fiber, or if it has ever been bent less then the minimum bend radius for the fiber. IF the exit fiber breaks or partially cracks,, you have one hell of a hazard elsewhere, too.Yes, under certain conditions, LDs are really sensitive to back reflections, and in the fiber laser, that thing probably had a optical isolator on it..Also, trust me on this, not a good laser for stripping paint.You have a burner / engraver / modestly lousy cutter, unless your cutting / burning tissue...There is a forum member here who will PM me to remind me I should have just stuck to the safety and let you quickly blow your diode for his, and my, peace of mind. Often I agree with him...The power control on that laser would have been done with a beam sampler elsewhere in the larger system, so you just have a fiber coupled laser diode module.BE CAREFUL... Be more then careful, be downright paranoid about Laser Safety. PS, Vent the cutting fumes, they are incredibly toxic.Steve

author: MDM3D
author_rank: Contributor
timestamp: March 27, 2019, 03:25:51 am
content: Thank you Steve for the detailed response. This is why I came here and asked the questions.I have not purchased anything yet... for once I decided to do my homework before waiting for parts to arrive.I was unaware of the lasorb... I was guilty of planning on using a big zener diodeI am aware of the nature of this pump diode(learned by osmosis from a friend who has his PHD in optics) they were under the impression that it would service as a laser cutter fine if I could figure out how to power it properly, terminate the end properly, focus it, and keep a strong air blast on the focal point. Terminating and polishing the end are not large challenges as I have some old telecom fiber splicing tools.The machine would be in a steel box with no openings. The danger of the power levels that this is capable of has been stressed and conveyed numerous times. Safety glasses will be ordered before laser diode is purchased. and my mother will be on speed dial. No arguments here. I like my eyes. NO diy lasic for me.In the end however I would rather build a machine using a diode laser rather than a CO2 laser. I think that aligning mirrors and the other tasks that come with a co2 laser are more risky than this. Please correct me if I am wrong.Just trying to figure out if a $57 diode is worth powering.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 27, 2019, 02:19:36 pm
content: One, this unit has a smaller exit fiber core then most LDs on the market. So your energy density on target will be high with the right optics, which in this case will be the right short focal length lens.LD will need a driver, either surplus on Ebay for 100-200$ when the right one pops up, or 8 TO-220 size Fets in parallel on a decent heat sink.You'll want a spare diode...LD will need a suitable power supply... 25o watt Lambda or Meanwell... , something of a better PSU with low spiking at turn-on...Some of them can be modified as a decent current source, for forming your upper current limiting...1 Pair of Safety Glasses..A GRBL and LaserGrbl setup to make it useful 35-50$ for the Arduino Uno and some ULN2004 Buffers..A good start is here:http://www.diymachining.com/grbl/and here:http://lasergrbl.com/en/40-60$ worth of Chinese Stepper Motor Drivers...Some sort of XY and hopefully Z motion stage with motion steps about a spotsize apart. Freehand surgical type lasing probes to do hand carving are very useless, you really need motion control.Power supplies, cabling, enclosure, Estop, possible aiming laser, aiming laser combiner, lots of 40-60$ a piece mirror mounts of the MM1 or MM2 or KMS type... IR Viewing camera..Did I mention cooling?The good news is the Eye Safety glasses have good resale value,,,, :-)This is an expensive hobby, and it would help if you had access to a lathe, and even better yet, a friend with a milling machine.Otherwise you have to do the old trick of buying a pin vise, and have a hole drilled in it to clamp the fiber...Steve

author: MDM3D
author_rank: Contributor
timestamp: March 27, 2019, 03:34:04 pm
content: I plan on using linuxcnc, my background is in mechanical engineering, the mechanics and the motion control are a cake walk this would be my smallest and fastest machine. The main idea would be able to throw a sheet of painted pcb blank drill out the vias and spots for through hole components and the laser off the paint in the areas that need etching. One to two setups depending on single or double sided boards and much less time messing around with perfboard with the added bonus of "free" silkscreen". My electronics background has been self taught but I have no experience with lasers/laser control but a fair amount of electric motor power control ie servos for cnc machines. Lasers seem to need much faster response controls than electric motors. I have a full machine shop and measuring lab that I can use. The LD will be water cooled.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 27, 2019, 05:55:01 pm
content: CW Laser diodes are not spectacular at drilling copper.. Via drilling and copper milling lasers are almost always very short pulse, ie Q-Switched..Probably not a rewarding use of this particular LD, unless you like very, very thin copper... You'd have to put a laser sensitizing layer on the copper, something that starts the combustion and oxidation of the copper... That is not easy... To do what you want, you probably need a Q-Switched Green laser... While those are my cup of tea, and I have done cutting of thin copper sheet for battery making, you'd need at least 10 watts average power of 7 to 35 nanosecond Q-Switched Green pulses to make you happy. In other words, really high peak powers.See:https://www.spectra-physics.com/applications/pcb-manufacturingSteve

author: MDM3D
author_rank: Contributor
timestamp: March 27, 2019, 07:18:19 pm
content: Ah I apologize for the confusion The drill/endmill would have it's own spindle, the laser would just be used to remove paint and engrave. Currently swapping from v bits to route traces to drills/burrs/endmills makes the process tedious and I still do not have silkscreen yet. This setup would be a 60K rpm spindle for the drill/endmill and a laser mounted on the carriage to remove the paint to greatly reduce tool changes.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 27, 2019, 08:08:52 pm
content: That kind of paint burning it will possibly do... Might have to watch you don't cook your substrate. So you defocus..Steve

author: texaspyro
author_rank: Super Contributor
timestamp: March 28, 2019, 04:35:05 am
content: If you are just paint burning, etc a 30+ watt IR laser is the wrong tool. A couple of watt blue diode will work just fine... and be cheaper and way safer.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 28, 2019, 04:15:10 pm
content: Yeah, But if he wants to engrave anything that IR beam from a tight fiber would be a sweet deal. At the cost of having to build/rig/find a much bigger diode driver..Steve