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Advice on CO2 Laser Build

Discussion in 'Laser Cutters' started by 2x3 CNC, May 21, 2019.

  1. 2x3 CNC

    2x3 CNC Well-Known
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    Hello Forum!

    I have two very quick questions, and one medium length question. :) I have been trying to build a CO2 laser, and have had trouble getting the signal to activate the laser power supply. So I'm scrapping everything I have done and starting over.
    So I'm asking opinions on the following two questions:

    1. Which controller is more suited for a CO2 laser, BlackBox or xPro V4? (I'll be using UGS and GRBL)
    2. Which Meanwell Power Supply, 12V/29A or 24V? (I know it sounds like a dumb question, but I'm really not sure what power I need to run the LPS, motors, etc.)

    Also, any other advice on using these controllers and Power Supplies (other than the obvious... BE CAREFUL!!!)

    I want to buy this immediately so I can start on this build and need to get moving on it, so your quick response is MUCH appreciated!!!
     
  2. 2x3 CNC

    2x3 CNC Well-Known
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  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    In terms of driving a laser, the same. Decide on other specs like motor current, etc instead :)


    24v. Better motor acceleration when drive voltage is higher. Laser PSU powers itself.

    I'll extend on that with BE VERY CAREFUL! Always have one hand behind your back when working on these (So current cannot form a path across your heart), Always wear appropriate goggles. Build a SOLID METAL enclosure, acrylic is cut by lasers, which makes it useless as a safety barrier.
     
  4. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt Thank you for replying to my questions! So I'm a little confused... the 12V/24V mains can't actually power the 40w CO2 laser tube?
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    No CO2 Lasers need Kilovolt power supplies! You can run little Diode lasers directly off 24v, 2.8-6w max, and thats 445nm (Blue/UV) which only works on Organics. CO2 lasers excite at 12-20,000v (12-20kv) and produce light with a 10600um wavelength (infrared) which is absorbed well by organics and also plastics

    Lots more research for you! :) CO2 lasers can really get complicated!
     
  6. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt Well, that makes complete sense! Duh on my part. I really appreciate your response! Can I control the Laser PSU with one of these controllers? As far as the other stuff, I'm just running 3 NEMA 42 motors (using parts from the Eleksmaker A3)
     
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Nema 17s?


    Yeah, but note that CO2 PSU wiring depends a lot on "which one you got" too...

    If its one of the decent ones they have the following pinout

    WP = Water Protection = Grounded out by a flow sensor in the water cooling line (GNDed when water flows, Open circuit when water flow is obstructed/off - Disables the tube to prevent it cracking if theres problems with water cooling system)
    IN = Power setting = Analog voltage, or tie to 5v if you run PWM into TH/TL (As for Grbl) - can also be wired with a potentiometer to set Maximum power (scale the PWM)
    TH = Trigger High = Wire to Grbl PWM pin - With IN tied to 5v (100%) the PWM signal on TH will scale power accordingly. Note super cheap PSUs doesnt like PWM!
    TL = Trigger Low = not used, inverse of TH - triggers when pulse goes low. Some people wire a switch to TL<-SW->GND to act as a TEST button
    5V = 5v output for the IN signal / potentiometer
    GND = Common Gnd for logic signals
     
  8. 2x3 CNC

    2x3 CNC Well-Known
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  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The ebay listing isnt really showing the pinout, so consider this the generic answer:


    Yes... if the PSU has a TH. Those cheapies tend to have TL (Labelled just L (Low)) and no TH pin, so check your closely

    If it has no HIGH input you can Wire in an inverter circuit to turn the high pulses into low pulses for the TL/L input

    32409723-dbfc734c-c1a8-11e7-9af3-17429ac12b57.jpg

    R1 and R2 = 1K Ohm
    use a NPN transistor e.g. 2N3904
    Wire +V to 5V
    Vs = Connected to PWM pin, and Ground connected back to the common GND
    VO = inverted signal to TL/L
     
  10. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt That is very awesome of you to take the time to show me that circuit! Thank you!

    This is a better diagram, of what I have:
    http://www.cncoletech.com/download/PS40-3-g.jpg

    So on this one, the VO signal from your (very awesome!) circuit goes to the "L" pin #3 on the 6-pin connector (third from the left)? Does the "G" Pin #4 need to return to the xPro V4 "Analog Ground" on the Output Connector?
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    GND should be common among all components: From the PSU GND, to Controller GND, to LPS Logic GND. To avoid EMI issues one would want to use star grounding, common point somewhere, i'd use the PSU's [-] terminal.



    Be aware of FG = frame ground = dont common that with DC ground as arcs from the tube to your frame/enclosure will happen (Dead tubes send arcs out the sides)
     
  12. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt
    Sorry, which digital ground? I see several of them... which one goes with "Spindle PWM Voltage"?
     
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    They all go to the same ground plane internally
     
  14. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt
    Awesome! Thank you so much for your help with this. I'm going to order the xPro V4 and the components you specified and try to figure this out!

    Thank you again for your help and time!
     
  15. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    :) Also consider the BlackBox - beefier stepper drivers = faster acceleration = something you'll miss when you try do raster engravings on smaller drivers
     
  16. 2x3 CNC

    2x3 CNC Well-Known
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    @Peter Van Der Walt Thanks for the advice! Will definitely do... unfortunately seems to be out of stock, which kind of stinks.

    So then I'm assuming use the 24V Power Supply, yes? (again for NEMA 17 motors)

    Also, everything we've been saying to connect it to the LPS would just use the PWM and the GND on the "TOOLHEAD" outputs, yes?
     
  17. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    New stock should be there today or tomorrow i heard.

    24v is always best

    Yes, gnd and pwm.
     
  18. 2x3 CNC

    2x3 CNC Well-Known
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    Awesome! Thank you again so very much!
     
  19. Alex Chambers

    Alex Chambers Openbuilds Team
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    Blackbox appears to be in stock at the moment, but they sell quickly!
    Alex. :D
     
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  20. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Indeed! Jump on it while you can!
     
  21. 2x3 CNC

    2x3 CNC Well-Known
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    Already bought it!!!
    :):):):):)

    Thank you gentlemen for your help!
     
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