1. #1
    Hi sorry if this is in the incorrect place, but i have built a Cnc machine all ali but i have a fault with the estops
    the cable for the motors is all shielded but the Estops are not, they use five core telephone cable.
    i think its the Earths .
    i have a filter before the vfd which is plugged in to my garage socket, the vfd is out side of my control box and then the wire to the spindle which is shielded.
    the motors have shielded cable but are not earthed. the top and bottom of it is i am crap at electrics and need to know what to earth and what not to earth
    and where, if some one could point me in the right direction that would be a great help.

    I use Estlcam Cam software
    with and Arduino
    Nema 23 Longs
    Longs DM542A drivers

    Cheers

  2. #2
    Something which sometimes makes a difference is to separate the mains supply to your VFD and control system.
    Try running your VFD from an extension lead plugged into the farthest possible socket from that which is feeding your control system.
    You could try swapping your E stop cables for twisted pair which are less susceptible to interference than straight cables.
    You think that's too expensive? You're not a Model Engineer are you? :D

  3. #3
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 2-3 years. Has a total post count of 59. Received thanks 23 times, giving thanks to others 5 times.
    Out of interest, what voltage are you running on the E-Stop line?

  4. #4
    I assume he's solved his problem and can't be arsed to feed back to the forum he asked for help.
    You think that's too expensive? You're not a Model Engineer are you? :D

  5. #5
    sorry i have not been back in touch my internet was canceled and i have just got it back up and running.
    the voltage is of my Arduino which is 5v but i have heard that if you run the Mega you can use 12v
    again my apologies for not getting back to you when you was kind enough to answer. not me at all

    ps the vfd is plugged into a five way adaptor the long type
    Again thanks
    Last edited by Slasher102; 3 Weeks Ago at 09:56 AM.

  6. #6
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 2-3 years. Has a total post count of 59. Received thanks 23 times, giving thanks to others 5 times.
    The motors, spindle, and VFD all put out quite strong and varying magnetic fields, which induce small voltages in the cables around them. The VFD can also pump electrical noise back into the mains supply, which can also cause problems.

    As magicminer says, you can use shielded twisted pair cable for your E-Stop line which should help to reduce the influence of the inducted noise.

    Magicminers other suggestion was to put more cable distance between the VFD and the control system power supply, which will slowly attenuate the noise. A 5-way plug doesn't really do anything - its cable length, and if possible filtering, that will impact this.

    At the moment, your signal is probably on (2.5V-5V) or off (0-2.5V) - meaning the noise only has to be ~ 2.5V to cause major headaches. If you increase the voltage on this line to 12V, the noise has to be on the order of 6V to cause the same problems. If you have an oscilloscope, you could measure what the level of noise is.

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  8. Quote Originally Posted by Slasher102 View Post
    the voltage is of my Arduino which is 5v but i have heard that if you run the Mega you can use 12v
    again my apologies for not getting back to you when you was kind enough to answer. not me at all
    Hmmm, Mega = Arduino Mega?, based on the AT MEGA 2560 MCU, still runs at 5V, but the on board regulator will provide the 5V required by the MCU. The I/O remains, however at 5V. AndyUK touches on ways to improve noise immunity, but with an Arduino-based system (and 5V logic) your best bet is to use opto-coupled inputs with a 12V (plus) input drive system onto the optos. The Arduino as-is is likely to be susceptible to noise.

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  10. #8
    i have been told that i need to put a 100nf capacitor as per the diagram and that should work,
    thanks for the help i will get some two core shielded cable as well.

    Cheers
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