LowRider Homing Switches

New Home Forum LowRider Advice – LowRider LowRider Homing Switches

This topic contains 6 replies, has 3 voices, and was last updated by  Jamie 1 month, 2 weeks ago.

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  • #102104

    kd2018
    Participant

    For those of you that are, how are you fixing your homing switches to the lowrider?

    This seems like a perfect spot for this switch for the x-axis, how would you fasten this here?

    #102116

    kd2018
    Participant

    Follow up question: would it matter, in regard to EMI, if I mounted a switch really close to a stepper? I mean right on it… A convenient place to mount the x switch might be to actually share a z motor mount screw.

    #102133

    Jeffeb3
    Participant

    This seems like a perfect spot for this switch for the x-axis, how would you fasten this here?

    Hot Glue?

    Follow up question: would it matter, in regard to EMI, if I mounted a switch really close to a stepper? I mean right on it…

    Probably not. They have pull up resistors on the board, so it’s pretty tolerant to emi.

    #102135

    kd2018
    Participant

    This is a LinuxCNC build, not sure about pullups. Switches and motors will be running on 24v.

    #102144

    Jamie
    Participant

    You shouldn’t have a problem putting the limit switch directly on the motor.  You had better have a pullup resistor one way or another — sometimes it’s internal to the CPU’s inputs.  If the input is floating then you will have random triggering no matter what, whether it is near the motor or not.

    #102156

    kd2018
    Participant

    Here is what the manual for my board says. I admit it’s a bit over my head. Little help re pullup/pulldown

    “ISOLATED I/O
    The 7I96 has 11 isolated inputs and 6 isolated outputs. All 11 Isolated inputs have
    a common pin. This common pin must be connected to
    ground for active high inputs and
    connected to the I/O power for active low inputs. The 6 isolated outputs are completely
    floating switches so can be use for pull-up/pull-down and mixed voltage switching.

    ISOLATED INPUT CHARACTERISTICS
    The isolated inputs use opto-isolators with a 4.7K
    input series resistance. This
    results in an approximate current draw of 5 mA at 24V. The inputs will operate with +-3V
    to +-36V signals relative to input common. Isolated
    inputs are relatively slow and not suited
    for signals faster than about 5 KHz. For sinking type inputs, the input common pin is
    grounded and a +3 to +36V signal is applied to the
    input pins to activate the input. For
    sourcing type inputs, the input common is connected
    to +5 to +36V and the input pins are
    grounded to activate an input.

    My plan was just to wire the switches in parallel to the appropriate pins, I hadn’t thought of needing any resistors. +24v -> n.c. switch -> input pin and then gnd -> input common.

    #102158

    Jamie
    Participant

    My plan was just to wire the switches in parallel to the appropriate pins, I hadn’t thought of needing any resistors. +24v -> n.c. switch -> input pin and then gnd -> input common.

    This will work.

    For most inputs that are not isolated and don’t draw any current, opening the n.c. switch will leave the input in an indeterminate state.  That indeterminate floating state is what the pull-up or pull-down resistor is needed to remedy.  In your case your circuit will work as you’ve described.

    1 user thanked author for this post.
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