Laser - Page 1
Forum section: electronics / general

author: akis
author_rank: Frequent Contributor
timestamp: July 08, 2014, 08:34:15 am
content: Has anyone built a home made Laser? I was wondering what is the best size/power ratio type? I know the CO2 is quite powerful but requires delicate glass tubes and large equipment with it, not really a portable device. I also read somewhere the CO2 is UV and invisible, which is a bonus.

author: Rerouter
author_rank: Super Contributor
timestamp: July 08, 2014, 08:44:47 am
content: The more important point is what is the end purpose? if its just for dicking around with i would not recommend much more than a laser diode out of a dvd burner, as a laser over that power level would realistically require purchasing a good pair of laser goggles at the wavelengths your working with,

author: Psi
author_rank: Super Contributor
timestamp: July 08, 2014, 09:29:10 am
content: Quote from: akis on July 08, 2014, 08:34:15 amCO2 lasers are far infrared, totally invisible except for the thing that's now on fire.Not really a bonus at all, unless your goal is to secretly set things on fire.They are very good at cutting/burning things though, most things absorb infrared instead of reflect it.eg, stuff like clear plastic which a visible laser would just pass through or reflect off appears totally black to an CO2 beam so it heats up and melts nicely with little loss.CO2 lasers are also relatively simple and easy to scale up for high power, eg 100WDisadvantages are, as you say, not portable or easy to use. They need gas and water cooling.For playing with, lasers a diode laser is far more interesting. A 8x DVD diode or blue laser projector diode will burn things if focused but wont cut anything except very thin items, eg 1mm thick.They will of course permanently give you eye damage if you get a direct strike, especially the laser projector diodes as they are usually 1-2W where as a DVD burner diode is usually around 300mWJust for the "cool" factor i recommend an Argon Ion laser.It wont burn anything but looks cool and is semi portable. Here's my one.1000W input about 25mW laser output, thats argon ion for youBe careful getting into lasers, they have a tendency to multiply until you have too many.Check out the last pic.

author: Fred27
author_rank: Unknown
timestamp: July 08, 2014, 10:01:57 am
content: I'd recommended a CO2 laser over a weedy little laser diode.http://www.buildlog.netis a good place to start for info on building your own.Personally, I decided to get one of the DC-K40 CO2 lasers you'll see all over eBay. They leave a lot to be desired in many places, but don't cost much more than the laser tube and PSU. I had planned to play around with this and then use it as a donor for a BuildLog 2.x style machine, but to be honest I only ever got as far as replacing thedreadfulcontroller board, adding a honeycomb table, coolant monitoring and air assist.I certainly wouldn't recommend a DC-K40 as an out-of-the-box consumer product, but for an EEVBlog reader who's happy to hack and improve electronics it could be a good starting point.Some more info on my experiences here:http://0xfred.wordpress.com/category/cnc/laser/

author: neslekkim
author_rank: Super Contributor
timestamp: July 09, 2014, 08:00:59 am
content: Quote from: Psi on July 08, 2014, 09:29:10 amIs it easy to drive those small lasers?, I bought some, about 5mW, I forgot my plan about them, but guess it was for visualization, but newer got around to test them yet.

author: Psi
author_rank: Super Contributor
timestamp: July 09, 2014, 10:01:54 am
content: All of those ones in my pic have built in drivers for 1.5-4V

author: neslekkim
author_rank: Super Contributor
timestamp: July 09, 2014, 11:54:07 am
content: ah, either I bought wrong, or maybe mine also have it then?, I bought this ones:http://www.ebay.com/itm/130953862380

author: Psi
author_rank: Super Contributor
timestamp: July 09, 2014, 12:05:59 pm
content: yeah, those look like raw diodes with some wires.The 1st generation of low power laser diodes are a bit tricky to deal with unless you have a proper diode driver.The usual kinda uses the built in photodiode inside the laser to form output feedback.The threshold between correct operation and overload is just too small on 1st gen low power diodes, so you need the feedback.The higher power diodes, like you get from a DVD burner, are much easier to drive.You can simply power the diode on its own using a LM317 in constant current mode.Most of the 1mW/5mW diodes you get in pointers today are actually ~20mW QC rejected diodes, or even proper 20mW rated diodes. They just drive them at 1-5mW to meet regulationsTherefor they can handle a bit more current than what's needed for 5mW output.It makes them a bit easier to drive without feedback.

author: akis
author_rank: Frequent Contributor
timestamp: July 09, 2014, 03:57:35 pm
content: It appears it is not simple to drive a laser diode, you need some sort of optical feedback modulating the current because with excess current it can be destroyed in ns!In terms of power, if I wanted to punch a hole through a 1mm sheet of aluminium (as an example) what powers would I need? If the beam strikes metal, does the heat spread as if I had touched the tip of my soldering iron to it? My soldering iron is 60W, would a 60W laser punch a hole?

author: ajb
author_rank: Super Contributor
timestamp: July 09, 2014, 06:54:07 pm
content: At a guess, you'd need several kilowatts of laser to cut aluminum. The problem is that in order to cut anything with aluminum you need to put a lot of energy into a small enough area rapidly enough that a very localized part of the material is vaporized without melting the rest of the work piece. Since aluminum is a very good conductor of heat, the rate at which you add energy to the target area has to be extremely high to maintain a steep enough thermal gradient to vaporize the material along the cutting line without melting the surrounding area. Adding to the challenge, aluminum reflects 90+% of most of the visible and infrared spectrum, so very little of the incident energy would actually be absorbed. I'm not sure about the absorption spectrum of aluminum oxide (some googling didn't turn up any graphs in units I understand), so that may or may not help.Anyway, laser cutting metal is not really a DIY-friendly project, especially as your first laser project. The optics will need particular attention, since focusing beams in the kW/cm2range is no joke.

author: ve7xen
author_rank: Super Contributor
timestamp: July 09, 2014, 07:46:05 pm
content: Depends what you mean by "build". Ben Krasnow is building a Ruby laser from (relative) scratch:I have also seen somewhere (probably here), someone using an optical power module designed for long-distance optical networking with a pulsed driver to punch (tiny) holes in stuff.

author: akis
author_rank: Frequent Contributor
timestamp: July 09, 2014, 07:54:30 pm
content: Many thanks for the explanation. How about firing at a piece of wood or plastic? What sort of "watts" would I need to make an impression with IR?

author: ajb
author_rank: Super Contributor
timestamp: July 09, 2014, 09:18:42 pm
content: Pretty much all of the commercially available 'small' laser cutters are int the 30-60W range. This is plenty for cutting plastics, paper, and wood up to around 7mm. You can get higher cutting speeds with more power of course, but above a certain speed the mechanics of the the thing become tricky. On our 30W Epilog, for instance, we simply can't do accurate vector cuts above ~20% speed because the gantry and drive system are not rigid or powerful enough to prevent overshoot on corners. You can cut thicker materials with multiple passes and/or a longer focal length lens, but edge quality deteriorates pretty quickly.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: July 10, 2014, 04:07:13 am
content: Quote from: akis on July 09, 2014, 07:54:30 pmI see zero signs of you giving a damn about safety. If you did, you would be asking questions about it concurrent with the questions you ARE asking. These lasers are NOT toys. Yes it seems cool but playing with them without getting the safety right first is the move of a fucking idiot.With high powered lasers it is not only the beam you have to worry about. Primary reflections, secondary reflections, tertiary reflections and even scattered light can all cause eye damage depending on the power and wavelength of the laser. Not just eye damage but skin burns, catch random stuff on fire over time, etc.

author: akis
author_rank: Frequent Contributor
timestamp: July 10, 2014, 07:51:22 am
content: Well I have many questions but can only ask so much. What "power" you need to achieve X is a general question comparing lasers to other mechanisms of applying energy remotely.

author: Fred27
author_rank: Unknown
timestamp: July 10, 2014, 08:06:50 am
content: PedroDaGr8 is right. Lasers are not toys. Get the right eye protection for your laser's wavelength. Take safety seriously.This is what an unfocused beam on low power did in about a millisecond.http://0xfred.wordpress.com/2013/02/20/laser-cutter-dangers/

author: Tinkerer
author_rank: Frequent Contributor
timestamp: July 14, 2014, 12:31:50 am
content: This is the same sort of danger as with any equipment like bandsaws and high voltage. Simply watch where you put your limbs at and dont do anything stupid. Eye protection is usually a good thing too.I have looked at how to make your own laser and things like that and its safe to say that its no small project, its one of those things that takes at the very least a good weekend to get going in any form, if you already have materials.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: July 14, 2014, 03:11:46 am
content: Quote from: Tinkerer on July 14, 2014, 12:31:50 amEye protection is a good thing with LOW power lasers. With HIGH power lasers its a MUST and only a fool doesn't use it. It only takes a fraction of a microsecond to cause permanent damage to the retina.

author: Psi
author_rank: Super Contributor
timestamp: July 14, 2014, 03:29:18 am
content: There was fog outside last night, so i grabbed the 200mW green laser