1. #1
    Hi All, Stupid question alert.


    I've got hold of a load of bits for my control box,


    Pictured Here
    Click image for larger version. 

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    (Yes I know the stepper drives are missing)
    I'm told the various bits need 14awg, and 22AWG wires.
    Now the question comes ,do I need single core, or multistrand , shielded or unsheilded, CY? SY? WTF! the more I look at the "Oh so many types of Wire", the more I'm baffled.
    I mean, Its wire, how hard can it be....

    For the AC Power side of it, I'm planning on using Boggo Standard Electrical flex and Kettle lead (IEC connector?) to bring the electrickery Into the box and to the powersupply,
    so I'm pretty much sorted there I think.
    Can anyone shed any light on what a contactor is , and do I need one?, as I believe it goes somewhere on this bit of the Control box circuit?

    If anyone has any tips or can shed any light on whats required, I'll be dead chuffed.

    In the mean time, I'm going grabbing some Ice for my ankle after my latest session with my PhysioTerrorist.
    Cheers
    Rick.

  2. #2
    For the stepper motors you need 4-core CY cable, which is shielded. If the cables are quite short then 1mm^2 is fine, but for a big machine I'd use 1.5mm^2 to reduce the voltage dropped across the cables.

    CY Cable - 4 Core 1.0mm2

    For the signal wires in the control box any thin wire would do and shielding whilst not necessary might prevent problems.

    You need fairly thick cable for the power to the drivers - similar thickness to the motor wires, so you could just use that if it saves buying more cable. Use separate wires to each driver - don't connect the power from one driver to the next to the next...

    A contactor is a switch that is controlled by an electric current, not by pressing it. Rather like a relay.
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  3. #3
    Quote Originally Posted by Jonathan View Post
    A contactor is a switch that is controlled by an electric current, not by pressing it. Rather like a relay.
    Can also produce quite a bit of electrical noise and large power drain so I'd avoid real contactors and just use normal switch's controlling lower power relays.

  4. #4
    Quote Originally Posted by JAZZCNC View Post
    Can also produce quite a bit of electrical noise and large power drain so I'd avoid real contactors and just use normal switch's controlling lower power relays.
    The emi emissions will mainly emanate from the spark when it switches, so if concerned about that I would use solid state relays (or some other solid state device, such as a transistor or triac if appropriate) since then there is no arc.
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  5. #5
    @Jonathon Stepper cables are sorted, Thems the ones in the bags in the pic (lower left x 4) , Its more signal and power wire in the box joining the PMDX126 and bits together. So I take it, it doesn't matter too much whether or not soild core or multistrand for either Signal or power? if not Ace! less headaches.

    I have a PMDX126, a 134 MOBO, and a 107 speed control board, so the wiring on those is pretty much plug and play with the 134 Mobo connecting the 126 BOB via ribbon cable, and the 107 is a daughter board mounted on the 126, so the wires in question would be any other wire from the BOB to power supply, etc.


    Them thar's 940 oz nema 34's and the machine is going to be a 4x4 bed when its born.

    @Jazz, Ahh Noise BAD, I see , So binning the contactor now I know what one is, for Power Isolation IE turning the machine on and offable, I do have a mains rated two pole switch that came with the kit, I take it that can be spliced into the power supply circuit without a relay.
    and If I'm powering things like E stops, then from the 48v DC side, Relays?

    Is it worth just bobbing into Maplins (insert cheaper shop here) and grabbing a few meters of bog standard non shielded 14 awg and 22 awg /metric equivalent, of various colours, I'm thinking I'll need some blue and brown, and maybe some earth for Power and black and white for signal?

    looking online is where my brain pops.
    What say you chaps?

  6. #6
    A contactor is essentially a big relay, however they're far more robust. The main benefit of a contactor is it should never fail to disconnect due to welded contacts. They physically move a link bar between each terminal, so if one contact should stick, the stronger spring will still disconnect the opposite end, whereas a relay only has one contact.
    Contactors generally use more power, due to the stronger spring.

    Officially, the e-stop should use a max of 24V, which then controls the main power via a relay/contactor.

    SSRs are an option, but aren't ideal for e-stop circuits as they can fail closed if overloade.

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