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  1. #1
    I have a 3-axis CNC kit from Zapp which consists of 3Nm steppers, M542 drives, 50V PSU and a PCPPS V3 interface board. Bought it some time ago but only just getting on with it. You know what these projects are like...

    For the E-Stop circuits, I'm going to use a Telemecanique contactor with a latching circuit and a reset button. Obviously all the stop buttons will be wired in series with dual N.C. contacts on each. I was planning to maintain a constant 24V DC supply for the safety circuit and then drop all remaining AC supplies which would be the Milling machine I'm converting, the 50V PSU and the PC. The PCPPS board would still be powered as it will be connected to the 24V DC supply. Will this setup cause any problems or risk buggering any of the components? I can probably cut the 24V to the PCPPS as well but may not have a N.O. aux available on the contactor.
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  2. #2
    Yes this will work fine and using relays it's basicly how I do all my control boxs. It's very Safe and much better at handling noise.

    Leave the PCPPS powered, Don't kill the PC power and if your using a VFD for spindle then Keep the VFD powered but kill the Run signal.

  3. #3
    Is K1 going to be the emergency stop contacts?
    If so why are you killing power to the pc. If you do this you wont be able to restart any jobs after an estop activation. You would need to home the machine again.

  4. #4
    You DON'T run mains voltage through an E Stop circuit!

  5. #5
    Right enough Andy, I missed that bit but the drawing is not complete and I just assumed that he would be using a 24VDC coil and usin the maintained 24VDC supply for the estop circuit and switching the 240V AC.

  6. #6
    Andy, there's nothing wrong with wiring the mains through the estop. Pro's like Strike CNC have been doing it for years! Lol

  7. #7
    Quote Originally Posted by Web Goblin View Post
    Right enough Andy, I missed that bit but the drawing is not complete and I just assumed that he would be using a 24VDC coil and usin the maintained 24VDC supply for the estop circuit and switching the 240V AC.
    Yes you are right it's not complete, I have assumed that K1 and K2 are the E Stop N/C contacts, no doubt birchy will be along shortly to clarify.

  8. #8
    Quote Originally Posted by Shinobiwan View Post
    Andy, there's nothing wrong with wiring the mains through the estop. Pro's like Strike CNC have been doing it for years! Lol
    It makes me cringe to think how many of their machines are out there still being used and a potential death trap!

  9. #9
    K1 is the 24V DC contactor. All the safety stuff will be run from the 24V DC supply, so the E-Stops will be 24V and NOT 240V. I've not yet drawn the latching circuit. The above drawing is only for the AC side of things and doesn't show any E-Stops. I do have a Pilz safety relay but am limited on space due to its height, so will use a contactor instead.

  10. #10
    240VAC can be used for estops but its not very common on machine controls these days. Most pro companies machinery that I have worked on always use 24VDC for control circuits.

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