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Blackbox 0-10V Issue

Discussion in 'Controller Boards' started by Paul Stoller, Jul 25, 2020.

  1. Paul Stoller

    Paul Stoller Journeyman
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    All of a sudden I'm not getting more than 100mV or so on the tool output when M3 S24000 (100% for my spindle).

    I've confirmed the wiring is correct still with no shorts or opens on either lead. Also the voltage measurement was taken with the leads disconnected from the VFD.

    I'm not sure what would have caused this.

    Does this sound like something that can be corrected or am I looking at a hardware failure.
     
    #1 Paul Stoller, Jul 25, 2020
    Last edited: Jul 25, 2020
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    1) 24v input present, powered on, etc? (powers the output opamp)
    2) grbl settings unchanged?
    3) measure PWM pin (0-10v is derived from the pwm signal)
    4) any recent changes?
     
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  3. Paul Stoller

    Paul Stoller Journeyman
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    Well don't I feel silly, I must have had the 24V supply turned off. Everything looks good now. Thanks for the reminder to check the obvious :)

    I had been working on the wiring in the VFD and had turned off everything, but when I powered things back in I must have missed the 24V supply. Since I was only testing the M3 commands I hadn't noticed the steppers were off.
     
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  4. Paul Stoller

    Paul Stoller Journeyman
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    This (or at least the 5V version of this board), is what I was adding to my VFD. This is a voltage comparator circuit, it's allowing me to add a safety feature I've been wanting for a while for my setup. This board allows me to take the 0-10V signal from the blackbox and it compares that voltage to a reference voltage that is set by the trip pot. By setting the trim pot at roughly 3V this allows me to have a minimum RPM of 0 setup in GRBL but if an M3 command of less than roughly 7000 RPM will result in the spindle shutting down on it's own avoiding a overheating incident.

    I just got to test it out and it works great.




    IMG_5934.jpg
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    There is a minimum frequency VFD parameter too that does the same. Don't have it offhand, but check the VFD manual. Commands below the safe frequency effectively gets ignored
     
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  6. Paul Stoller

    Paul Stoller Journeyman
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    It doesn’t work for my VFD, at least when I tried before the spindle wouldn’t fully stop.
     
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  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I may have the name wrong. One Minimum Freq sets the frequency range. There is a setting for that on most vfds though might be called something else. Either way, your module should work too, just check that it doesnt load the 10v line too much with both it and the VFD (check that voltage doesn't drop)
     
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  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    From the YL620a thread:

    Is the one I am thinking of (or i think thats the one) - check your VFD manual
     
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  9. Paul Stoller

    Paul Stoller Journeyman
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    Does this look right?

    PD073 Lower Analog Frequency
    Set Range:0.00—400.00 Hz Unit:0.01 Hz
     
  10. Paul Stoller

    Paul Stoller Journeyman
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    I gave PD073 a try and it did limit the VFD from dropping below the specified frequency, but the issue is that it just keeps the VFD spinning at that minimum frequency instead of stopping when it drops below that frequency.

    My circuit seems to be working as expected so I'm going to keep that in place.

    Also added in my safety switch in between DCM and FOR.

    IMG_6051.jpg
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    No EMI issues yet with the VFD that close?
     
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  12. Paul Stoller

    Paul Stoller Journeyman
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    Largely remains to be seen. It's well grounded and shielded but I've not yet run any long jobs on it where it's actually cutting much.

    I should be able to run some good tests soon now that the enclosure is done and I have vacuum and compressed air available.

    I just need to get some leaks in the vacuum system closed up and both the vacuum and compressed air hooked up to the coolant output on the Blackbox and I should be able to start some better tests to see if EMI is a problem.

    If I have to move it I could move it to the lower cabinet but would need to make up a new VFD cable and I'm not certain if I'll have a length of the good shielded cable left to do that. If it comes to it I'll get more cable and move it.

    Fingers crossed I won't need too
     
    #12 Paul Stoller, Aug 1, 2020
    Last edited: Aug 1, 2020
  13. Paul Stoller

    Paul Stoller Journeyman
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    Added a "spy cam" to the dust show in order to see how things are cutting as well.

    IMG_6052.PNG
     
    #13 Paul Stoller, Aug 1, 2020
    Last edited: Aug 1, 2020
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  14. Paul Stoller

    Paul Stoller Journeyman
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    On the EMI question, I’m still not certain if it will be a problem but as a precaution I’ve added ferites to all of the connections to the blackbox

    EF49EB18-2ACB-4D07-9E09-2226E612874B.jpeg
     
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  15. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    They never hurt :)
     
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