How to wire and configure led cross hairs for aligning cuts



  • I am trying to attach an LED cross hair to my spindle but I am curious as to where would be the best place to connect it to on a Duet3 and how would I configure it for the offset? Would that just be a G31 command to set the X and Y and then a G10 L20 P2 Z0 when i set the height?



  • Best to attach: What voltage and current do they need? Do you want them on all the time, or controlled from a Macro?

    Offset: Normal CNC technique to measure:

    • put a tiny diameter bit in the spindle.
    • jog anywhere. Zero the current work coordinate system (I usually do a G55 G10 L20 P2 X0Y0)
    • Spindle on and jog Z to drill a hole in your spoilboard
    • z up to clear the bit, spindle off
    • jog XY until the crosshair is in the hole

    XY display will now read the offset from crosshair to spindle. Write it down. Depending on where you put it, you MAY have to revers +/-

    Where to put it? You could make it any of several offsets. Personally, I'd build a macro that moves that amount. Something like

    G91 G1 X23.47 Y-41.32 F6000

    Or whatever.

    Then I could use the laser anywhere I wish, and invoke the macro to put the spindle over that spot.

    Oh, and check CAREFULLY that the cross does not move as you raise and lower Z. If it does, Mechanical align until it doesn't.



  • @Danal Perfect thank you,
    Im thinking if I could control with macro that would be great. This is the item here
    https://www.amazon.ca/gp/product/B07THH7SPN/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
    It says 3.0-5.0v
    I never considered the movement as I raise and lower it. Thats a great way to check if im having any mechanical issues. Thanks



  • Ah, and I forgot to ask about your board: Duet 2? 3?



  • @Danal Duet 3



  • Then I would put the Laser on a fan output, set that output to NOT PWM, and use a 12/24V converter to get the 5V the laser needs. There are probably other ways...

    The one thing to NOT do, is drive the laser from a GPIO out, like io0.out or similar. This might seem to work when you first test it, but a device that could easily be pulling slightly more than the mA spec of an output pin, that would make me very nervous. Because it could cause a CPU failure down the road, leaving you with an expensive paperweight.

    So,yeah, fan output is probably best. Then just turn that "fan" on and off with normal Gcode commands, for that fan nubmer.



  • @Danal said in How to wire and configure led cross hairs for aligning cuts:

    12/24V converter

    I thought there were spots on the duet that put out the 3-5v



  • There are... but they are very low current capability.



  • While even a low power laser (5mW, 20mW?) will draw more current than an io pin can source or sink it should still be sufficient current capability to get 5v from the duet and use the switched ground from OUT3-9.



  • @bearer said in How to wire and configure led cross hairs for aligning cuts:

    While even a low power laser (5mW, 20mW?) will draw more current than an io pin can source or sink it should still be sufficient current capability to get 5v from the duet and use the switched ground from OUT3-9.

    Those are the fan outputs to which I was referring. To your point, we could get 5V from another place. At the same time, wiring harnesses that attach to more than one plug make me a little nervous. That's why I originally recommended a 12V-5V.

    Despite my nerves, there is absolutely nothing actually wrong with doing it that way, so lets document it:

    @chichirod, wire the laser black wire to, say, out9 (or whichever number, 4 through 9). Leave the VOUTLC2 pin in out9 unconnected. Wire the laser red wire to any unused connector with "5V" and a solid red block. For example, the dotstar, or any of the io_3 through io_8, etc. on this diagram: https://d17kynu4zpq5hy.cloudfront.net/igi/duet3d/TF1FBCbopEsxvYAv.huge

    Then define a fan to that out9 connector, and use commands to turn that "fan" off or on to turn the laser off or on.



  • Actually if a 100R series resistance and 35mA current is sufficient it could be driven from out9_buff on the laser header; that would be the only way to not connect to more than one header in any case.


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