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Thread: CNC Bridgeport retrofit

  1. #61
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    I could set the granite drives up that way but I am going to let USBCNC take care of homing and estop (which relies on the switches and not encoder lines)

  2. #62
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    Quick question, Can i operate a 24vdc contactor coil with 24vac?

  3. #63
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    The impedance of the DC coil on AC is going to be higher so the contactor armature may not pull in or if it does, hold in weakly or chatter, put a simple $3.00 bridge on the coil.
    On AC a fast pull in relies on the low DC resistance of the coil causing high inrush and the time it takes for the armature to close after which the impedance becomes effective and limits the current, introduce the high resistance of a DC coil and you may get the effect above.
    Plus the shading ring is absent on a DC contactor coil that prevents chatter on AC contactors.
    Max.
    Last edited by MaxHeadRoom; 03-19-2012 at 01:30 PM.

  4. #64
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    Thanks max

  5. #65
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    pulse generator came in. going to get my control sheet metal going this week



    now waiting for a 50 pin header to terminal BOB in mail and then I pretty much should be done purchasing stuff
    Last edited by legendboy; 03-20-2012 at 03:01 PM.

  6. #66
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    made some smoke last night

    i wanted to power up my control to check limit switch and estop functionality so i went ahead and connected main power with only fuses in to power the control ps.

    i didn't want to listen to my contactor buzzing so i disconnected one leg of the 24v coil leads from it while power was on

    my 24v transformer started smoking as soon as i did that. i think this happened because i am powering the little transformer 240v so one hot leg was still attached

    not sure exactly why smoke tho

  7. #67
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    There is a piece of the puzzle missing, no load should = no current, it sounds like something shorting the transformer secondary?
    It Doesn't matter if the primary is still connected?
    Was it the 24v or the 240v side you disconnected?
    Max.

  8. #68
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    it was the 24v side


  9. #69
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    The transformer is marked:

    Pri: wht-com
    Blk-120v
    Red-208v
    Org-240v

    I had 240v mains connected to black and orange

  10. #70
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    Looks to me like it should have been wht and org you had 240v connected to a 120v input.
    Max.

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