Alright, some background. I bought a laser, added to my CNC which is using a CNC XPRO V5 as the controller. Jumped through all the hoops and got a lot of help here to make it all work perfect. I have been using buck convertors similar to LM2596 DC-DC Switching Adjustable Step Down Voltage Regulator Module 4.5V-40V. I put the convertor inside a 3d printed box with a switch, an attempt to make it safe and protect it. This may have been a bad idea as I had 2 fail. Think it may have been overheating I took the cover off the box and the 3rd has been fine. I have been worried about it failing mid use so I bough a 12v power supply, this one, thinking it would be more stable. The funny thing is, when I hooked up the 12v power supply and turned on the switch for the laser, the laser turned on even though it was not getting the PWM signal to turn on. I did some trouble shooting to what made sense to me and came up with nothing. I put the buck convertor back in and all seems to be well. So the real question is why/how in the world would a new power supply cause my laser to turn on without having a PWM signal? Can someone please suggest a better option if there is one? Thanks a bunch!
Depends what kind of laser. How much current does it need? Lm2596 (the genuine old National part) could do 3A. The chinese clones clonk out around 1A and they rarely come with a 3A inductor (those black square inductors can't handle 3A either). Pulling a lot of current and casing it up is bound to overheat and kill it. As for the PSU, would have to test it out look for isolation problems etc. Stick to a good brand like Meanwell - those cheap LED supplies cut a lot of corners
It was very likely overheating, but (if genuine) the LM2596 has thermal shutdown protection - once it has cooled down, it will reset once the external power is removed. I used one for my small LASER and ran into a similar problem. There simply isn't enough area in those small boards to dissipate the heat generated at moderate current output without an additional heatsink. Put it inside a plastic box, and the situation is much worse. I put an aluminium lid on my box and mounted the module inside that, with the chip thermally connected to the lid and have had no further problems.
Alright, the laser claims to be an 80Watt laser with 10Watt output. I don't have a great handel on Electrical Engineering but this is what I think I understand. at 80W and 12v that is 7 amps, but at 10v its 1 amp. If I was pulling 7 amps, woukdnt the buck convertor fail if its at 3 amps? Meanwell has a small 12v supply at 8 amps, would that be a bettet option or am I looking at this wrong?
All marketing. Laser diodes peak out around 5w actual optical power. Industrial | LD | NICHIA CORPORATION (See Note below) (Can be overdrived to around 6w with good heatsinking, 10w sounds like a stretch unless its got water cooling or some other more active type of cooler) The https://led-ld.nichia.co.jp/api/data/spec/ld/NDB7Y75.pdf for example pulls 3.5A at 5V to deliver 5W optical (rest burned off as heat, note huge heatsinks around diodes) 3.5A * 5V = 17,5W That does imply the module itself has a stepdown/constant current driver on it (12V in, 5V 3.5A out) - which if there was no other losses (fan, heat burned off by onboard driver, resistive losses) would be at least 1.46A at 12V (but there are losses, so probably at least 2A constant) - skip theory and measure current draw with multimeter on 12V side with laser at full power if you really want to know - theory is only going to get you so far 2A though even a proper LM2596 will need some heatsinking (bigger PCB, 4 layer with proper power pad thermal design) Even further, TI's https://www.ti.com/lit/ds/symlink/lm2596.pdf?ts=1738141523410&ref_url=https%3A%2F%2Fwww.mouser.de%2F can do 3A but if its a module with a chinese clone, whats its real rating? NOTE BELOW (referenced above) If you spend a little more, there are "modules" over 5W: Opt Lasers PLH3D-15W Engraving Laser Head: Woodworking, Leathercrafting, Textiles & More! for example, has 3x5W diodes inside They shine the 3 diodes down one optical path using lenses and prisms combining their power into one beam
I took your advice and measured the current draw. It peaked at 3.1. My laser has diodes in it. So, is better to keep the buck convertor and make sure it stays cool, or should I get a power supply that has 3.5-4 amp raiting? My limited understanding leans to a power supply.
I would vote for a good quality power supply, but a little more generously rated than that - Maybe at least 5 amp so that it doesn't run too hot when supplying ~3A continuously.
