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CNC xPro v3 - very little voltage on PWM output

Discussion in 'Controller Boards' started by Siez, May 9, 2019.

  1. Siez

    Siez Well-Known
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    I have a CNC xPro v3 wired up to control a Super-PID, but have never been able to get the PWM output working for RPM control through OpenBuilds CONTROL.

    Using CONTROL, if I turn on the spindle I get about 0.045v off of the D11 PWM output. When turned off, it's right at 0v which is spot on. I've tried various levels of spindle RPM using the M3 Sxxxx command, but no change in the output voltage.

    I'm stumped. Any ideas?
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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    M3 S1000 where 1000 = the same as the value of $30 : gnea/grbl

    (Grbl scales pwm between $30 and $31 (For example if its a 10000 rpm spindle you want to set $30=10,000, and also send M3 S10,000 to set 10krpm )
    Check that your $30 = 1000 as well then M3 S1000 should be 100%
    Remove anything that is hooked up when measuring of course, as it may have a drain/short dropping the voltage. Check with the XPRO on its own first until you get 5v out at M3 S1000 (With $30=1000 or adapt to whatever $30 is)
    Also make sure you dont by accident have $32=1. Laser Mode will change the behaviour of the PWM pin (Only on during g1 moves)
     
  3. Siez

    Siez Well-Known
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    Thanks for the reply. I had everything set correctly, but one change I made was to drop $31 from 5000 down to 0, which helped. Is there any chance in the future to be able to edit the default RPM when turning on the router/spindle? I know I can create a macro for the speeds, which I've done, but it's one more screen to traverse.

    I might as well toss two more questions out there while I'm at it. If need be I can always toss these into separate threads, but they are sort of related.
    1 - The SuperPID used PWM to set the speed of the router, but it also requires a 0V signal to turn the router on. Since the CNC xPro only outputs a 5V signal from any of the outputs when they're trigged to an "On" state, I'm using a relay to pull the signal low, which works but seems ... clunky. I'm currently triggering off of the Coolant output. Any better ideas for how to trigger the "Run" state on the SuperPID? It would be great if there was a way for it to turn on when I start a job, as I've forgotten once or twice and crashed the non-turning bit into the workpiece. :banghead:
    2 - Correct me if I'm wrong, but it appears that the xPro gets it's operating voltage from the USB connection. For some reason mine is only getting 4.6v, which does cause some limitations. I didn't see any pots or other methods to tweak the incoming voltage, so I guess I'm stuck with less than 5V?

    Thanks again!
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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    At this time 99.9% of our users are using Routers as spindles, so trying to cater to the majority, and the main goal is always to avoid needing a "configuration dialog" - so at this time and near future, unfortunately not. Besides, once you are doing real work you wont use the menu anyway... Your S commands will come from your GCODE post processor :)

    Extra mosfet? A shame they dont have an option onboard the SuperPID like a jumper to select high or low. Speak to them though, they may have a goto solution they suggest for this.
     

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