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  1. #1
    Join Date
    Sep 2011

    Question ESS C25 BOB home switch wiring


    I am upgrading my old 3 axis Mach3/C10 based controller to an ESS with a C25 BOB and Mach4. All the outputs, including the motors and spindle relay run perfectly. But I am having trouble with the home switches. They appear to be latching in Mach4 and not clearing when the switch is released.

    Can someone please tell me the best way to wire the home switches to the C25 BOB? I currently have them connected to Port 2, pins 2, 3 and 4. Should I be connecting the other side of the switch to GND or to 5V? Do I need a pull up/down resistor? Should I have them configured as active on high or low?

    Thanks very much in advance.


  2. #2
    Join Date
    Aug 2010
    I just wired up my 3 axis machine with similar hardware. While doing so I ran across a wiring diagram that may help. Here is a link:

    You may have to login to see the info but the drawing they have listed as an example provide good reference on wiring your switches. Also remember there are two location to change your I/O setting. One in mach 4 and the other in the ESS plugin. Some changes should only be made in the plugin, maybe that's the issue your having if your wiring is on point. Hope that helps.

  3. #3
    Join Date
    Sep 2011

    Re: ESS C25 BOB home switch wiring

    Thanks, mate. I appreciate the help.

    This is how I wired them up and, so far, they seem to be working well.

    Attachment 412344

  4. #4
    Join Date
    Mar 2007

    Re: ESS C25 BOB home switch wiring

    I did not see the original post until now

    if you look at the C25 input diagrams in the manual

    Attachment 412348

    you will see a 4700 ohm pull down resistor plus a LED with a 220 ohm current limiting resistor

    the resistors shown in post 3 are a good idea as they will limit the fault current if a home switch wire is shorted to ground

    the downside is the reduction in voltage at the C25 input when the switch is closed

    assuming the volt drop across the LED is 2V about 1.2V will be dropped across the two paralleled 330 ohm resistors

    reducing the C25 input to 3.8V

    while this should be enough to be a valid logic high it may make the system more susceptible to noise

    if that is the case reduce the resistors from 165 (330//330 = 165)
    try 47 to 100 ohms

    the compromise being having the resistance low enough to bring the C25 input near to +5V
    without needing a high power resistor to dissipate the heat under short circuit conditions

    for example
    a 47 ohm resistor 0.106 A will pass through the resistor when connected across the 5V supply
    and would dissipate 0.53 W
    I would use a 47 ohm 1W resistor

    when a 47 ohm resistor connects a C25 input to +5V
    about 0.5V will be dropped across the 47 ohm resistor
    so the C25 input will be +4.5V


  5. #5
    Join Date
    Sep 2011
    Thanks, John. I appreciate you sharing your knowledge. I will give that a try.


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