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IndustryArena Forum > CNC Electronics > CNC Machine Related Electronics > mini mill spindle switch between Mach & pot
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  1. #1
    Join Date
    Feb 2004
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    1311

    mini mill spindle switch between Mach & pot

    Hello, (I posted this in the bench top area but here seems more logical) I have my X2 mini mill spindle under Mach control now (via a Gecko G540) and I want to add a switch so I can have manual(pot) / off / Mach control. got this On-OFF-ON SPDT.



    I have the 30-10006 version.

    I've seen similar setups and would think this should work. I have the line from the pot wiper going to terminal 3, from my G540 VFD signal to terminal 1, and terminal 2 is connected to P2 on the motor control board.



    But the behavior is odd so I must not be understanding something. When I have the switch ON for terminals 3-2, the pot controls the spindle like I would expect. At this point, my G540 is off while I test. Then, when I switch to OFF and click the spindle POT on but leave it at low, the spindle goes to full speed and the pot is ineffective. When I switch to ON for terminals 2-1 - which should be Mach control - I also get full speed when I click the pot to on and low (again, the G540 is off while I test so I would expect the spindle to be stopped) and the pot is ineffective. According to the switch's circuit diagram, this switch should work. I've tested Mach control through the G540. I don't want to turn on the G540 to test it until I have the manual pot working like I would expect. Anyone have any ideas on what I'm missing?

    cheers,
    Michael
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  2. #2
    Join Date
    Jan 2006
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    2985
    The common terminal should be connected to the analog input on the actual VFD. The pot should be connected to 10V and GND, with the wiper connected to one terminal of the switch. The gecko output should be connected to the other terminal of the switch. The VFD, G540 and Pot power supply must all have common grounds for this to work right. A full schematic of what you have going on would be helpful.

    Matt

  3. #3
    Join Date
    Dec 2003
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    24216
    I would think you could get away with a single SPDT, no centre off, although yours should work, if you connect the outer ends of the pot to P1-P3 and also leave the analogue power for Mach connected and wire up the switch the way you have it, it should work?
    Is this what you are doing, basically?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
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    Feb 2004
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    Thanks guys. Firstly, here is a schematic. I am doing exactly what PMinMO described here. In fact, I implemented the 1st scenario, G540 only, first to make sure that worked. It did. Then in 2nd scenario, I simply replaced the relay with the SPDT on-off-on switch. Otherwise, it is wired identically but without the 12 v power supply and lead to output pin 17 of course.

    Thanks Al. I thought it would be nice to have an explicit OFF position so I picked up this SPDT on-off-on switch. I tested the switch and it does work as described. That is exactly what I am doing.

    cheers,
    Michael
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  5. #5
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    Dec 2003
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    I would think that by intercepting P2 and Term 8 as you have done should work?, as long as you use the power from P1 & P3 for analogue supply?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #6
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    Feb 2004
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    1311
    thats what I thought!?
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  7. #7
    Join Date
    Feb 2004
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    1311

    5 minutes with a voltmeter...

    Ok, this explains it but adds more questions!

    I basically disconnected all of the leads from the switch and used a multimeter to verify the connections to the pot. Rehooked up P2 and the pot works as expected and P1, P2 and P3 were verified. Then I disconnected P2 from the pot leaving only the ground and V+. Guess what, the spindle comes on and speeds up to full RPM no matter what the pot is tuned to. I do not understand that at all. Basically, with P2 floating the spindle controller is feeding +10V to the circuitry that powers the motor. That's why I saw what I saw. Now, if I have a simple SPDT switch hooked up as described above AND if the G540 is powered up, then switching back and forth should work as expected. But, I don't know what will happen if the estop is enabled - I need to measure the output from the G540 with estop to make sure it is grounded and not floating.

    Does this make any sense? I would have thought that no connection to P2 on the controller board would not give full speed. Maybe that is why PMinMO implemented the relay powered by a G540 output. If the G540 is off, then only the pot would be enabled. The output from the G540 can only be enabled if the G540 is on and can switch the relay. Kind of clever but should have been mentioned if that's the reason!

    cheers,
    Michael
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  8. #8
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    Dec 2003
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    What it indicates is that the input is fairly high impedance, usually an Op amp, this will have some kind of very high impedance bias or feedback taking the op amp full on, the pot when it is connected being relatively lower impedance will be in sole control of the input to the Op amp.
    My take.
    One reason why I mentioned a sw with no off posn.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
    Join Date
    Feb 2004
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    1311
    Thanks Al. That being the case, even a switch with no off position could be a problem if the G540 is disabled or off for the same reason right? That would mean the operator (me) would have to be careful about the state of the switch when powering up. In reality I expect to be under Mach control the vast majority of the time.

    I have a CNC4PC C6 spindle speed control board to use on my other mill (G0704). It will be interesting to see if it has the same behavior.

    cheers,
    Michael
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  10. #10
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    Jan 2006
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    2985
    A triple throw switch would allow connecting a "short" or pulldown resistor to the analog command which would make it stop in the "off" position.

    An e-stop should trigger the "enable" input on the vfd, or kill power to the vfd altogether, or both. The analog command should have no impact on it's behavior in an estop situation.

    Matt

  11. #11
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    Dec 2003
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    I was just about to suggest you could try a 1meg or even 500k resistor from P2 to P1, connected permanently, it may solve the problem, depending on the actual input impedance?
    I should not hurt to try it?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  12. #12
    Join Date
    Mar 2007
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    2083
    Hi michael ,

    you are likely to find the control voltage connected to the control board will be smoothed by a capacitor

    when the switch is in the off position, the voltage can take some time to decay to zero

    the best way could be to use a 3 way rotary switch to ground the speed control input in the "off " position as in the first diagram

    or if you use a KB electronics speed control

    a two pole rotary switch can be used to connect the I1 and I2 terminals together , in the "off" position

    I1 and I2 terminals shown in the second diagram



    john
    Attached Thumbnails Attached Thumbnails speed control switch.jpg   New KB electronics I1 I2 terminals.jpg  

  13. #13
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    Feb 2004
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    Thanks gents.

    John, this is a XMT-1135 board commonly used in mini lathes and apparently Micromark uses in its X2 mini mill. I do have a KBMM 125 for my G0704 though that I'll be wanting to setup this way.

    Al,I can give that a shot. I am leaving for a week tomorrow and don't have the resistors in shop.

    I looked for a three way switch but my local electronics store didn't have them. I would prefer a rotary but looking at Mouser's selection was daunting and it wasn't clear if they come with knobs!

    cheers,
    Michael
    Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
    www.EclecticAngler.com | www.ReelLinesPress.com

  14. #14
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    Jan 2006
    Posts
    2985
    Radio Shack should have a suitable resistor.

    I normally use digikey for components, their search is superior to others IMHO.

    The rotary switch most likely does not come with a knob.

    Matt

  15. #15
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    Dec 2003
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    Quote Originally Posted by mhackney View Post
    John, this is a XMT-1135 board commonly used in mini lathes and apparently Micromark uses in its X2 mini mill. I do have a KBMM 125 for my G0704 though that I'll be wanting to setup this way.
    Michael
    That is a very simple basic circuit for that control, The KB/Baldor are a little more sophisticated.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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