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Help!! Laser trouble, not switching..

Discussion in 'Laser Cutters' started by Jon Bickley, Nov 26, 2019.

  1. Jon Bickley

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    I have fitted a laser to my cnc router, I am using an Xpro V4 with grbl 1.1h.
    I have changed $32= 1 $ 30=255 and $31=0. I've downloaded lightburn and openbuilds controller but I'm having the same issue with what ever I use.
    When I power the laser up to cut a file it moves around exactly as it should but it wont switch in and out.
    I have connected to the spindel output and anolog earth. The spindle led flashes away when the file is running but has no affect on the laser.
    If I reverse the connections between pin 11 and earth the laser switches with every flash of the led.
    Only thing is it switches on for the travel and off for the image!!
    I've been pulling my hair out I just cant seem to crack it..
    Any help with this issue will be gratefully received.
    Many thanks in advance.
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Can you post pictures of the laser and connections?
    (It might be a bad-chinese-copy laser that needs an inverted PWM signal to work, some are badly designed that like that, in which case you need to wire up an inverter circuit (couple resistors and transistor)
     
  3. Jon Bickley

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    Hi Peter thanks for the quick responce.
    Here are a couple of photos.

    78841370_781334222280609_945487636615659520_n.jpg 78337864_786172805181538_1966631564531990528_n.jpg 78113238_593874298024438_257330650552467456_n.jpg
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Module looks familiar, don't recall there being issues with it that we've seen yet

    If you are able to see, does the LED react correctly? (On when it should be cutting?) or is the LED reacting the opposite of the laser? - this will at least help us eliminate grbl+gcode+settings if that is reacting correctly.

    I don't have the schematics on hand to confirm of the Analog gnd is connected to digital gnd, but worth a shot testing with a digital gnd?
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    And you are using stock standard Grbl, not someone elses (or included in some application's flashing tool?) that might have been compiled with inverted outputs?
    (OpenBuildsCONTROL can flash Grbl 1.1f for you - we know that works)
     
  6. Jon Bickley

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    The led does appear to flash at the correct time but cant be 100% as the laser doesnt react.
    I did try digital ground to but didnt seem to work.
    I will try reflashing to 1.1f with CONTROL and see what happens.
     
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  7. Jon Bickley

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    Hi Peter,
    I have re-flashed using CONTROL and I now have grbl v1.1g. I didnt get an option to flash to 1.1f.
    I have tried both analog and digital ground but am still having the same problems.
    The pin11 led seems to be flashing on and off at the correct intervals, on when cutting and off when traveling.
     
  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Sorry! Forgot we updated already (; But yeah, still a good base to know its not because of a compile time option, so must be hardware related (always a shame with the chinese products and lack of standardisation right)

    As expected, so sadly, you are in for either fixing that laser driver's inverted signal or replacing it with a good (OPTlaser, Jtech Photonic etc) branded one :(

    You can try using an inverter circuit to flip the off's to on's: https://www.electronics-tutorials.ws/logic/logic_4.html (on the PWM signal output before it hits the module)
    Or if you have the skills, reverse engineer the board and see if there isnt an onboard inverter that you can bypass instead
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Oh, one other thought, looking at the pictures again. There seems to be two PWM inputs? Have you tried both? (One may be inverted and the other not)
     
  10. Jon Bickley

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    I have tried both inputs but get the same issues.
    will have a go at fixing the signal, will let you know how it goes.
    If I have no look is there any thing you can recomend to replace it?
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Jtech Photonics or OPTlaser
    Anyone claiming they have more than 6w for sale is lying (; thats the limit of the technology at this time
     
  12. Jon Bickley

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    Hi Peter, hopefully the components I need will arrive in the post tomorrow.
    I have followed the link you gave me and have the circuit design which looks simple enough, but once I have built it I'm unsure how or where to put it and how to connect it.
    Could you help me with this and give me a few pointers please?
    Maybe even a simple diagram.
     
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    :) If you can give me a day or two (and don't mind reminding me again if I forget) I'll wire one up on a breadboard and take some pictures for you - iI'd rather build it so I know it works then give you the details) (Monday is just a tough one, so lets see later in the week please )

    In the meantime, Youtube for Inverter with Transistor should give some tutorials too!
    The inverter changes the input state to its opposite, so the PWM signal that looks like _-_-_ comes out as -_-_- as we know your laser fires when its low, and off when its high, that should reverse the signal so off=on and on=off
     
  14. deduch

    deduch New
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    Hello. The brand of laser heads is "Opt Lasers". Thanks :)
    A 12 W laser exists. This is true, it is based not on a single diode, but on a system using 2 laser diodes.
    PLH-12000 - High-power professional Engraving Laser Head
     
    #14 deduch, Dec 2, 2019
    Last edited: Dec 3, 2019 at 7:17 AM
  15. Jon Bickley

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    Finally got it working!!!
     

    Attached Files:

  16. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Sweeet! Inverter? or some other trick (for future reference)
     
  17. Jon Bickley

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    I did use an inverter but I think it may work without.
    I had to connected pin11 through a 3K resistor and to the collector, the laser was linked off this after the resistor.
    The base is connected to the spindle direction pin and the emitter to ground. FB6281E6-80A7-4D86-B3D8-EAA224E83B94.jpeg
     
  18. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Sweeet, inverters for the Win!
     

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