Homing/Limit Problems – TinyGv8

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  • February 24, 2015 at 6:27 am #7444
    moeter
    Member

    I have major problems with the homing sequence. My setup is as follows:

    4 Axis movement, optical and inductive initiators as minimum and maximum switches. I am using the current edge (438.02) build.

    Homing works fine if (and only if) the axis are in their working range. When they are either in the homing or limit switch, all fails miserably:

    Case A: Limit switch:
    The axis moves out of the limit switch, and then back in, leaving the robot in the same state as before.

    Case B: Homing switches:
    The axis moves further to the mechanical limits of the system, homing therefore not successful.

    The switches are correctly set to NC, there is a high level on the switches inputs if the axis are inside the working range. Something else that worries me is that if the robot is switched on, and a limit/home switch is activated, the robot can move that axis in any direction, until it moves out of the limit switch. Then the limit switch error is thrown.

    Apparently, switches are initialized inverted if they are active during startup. Is there any way to change that?

    Thanks a lot!

    February 24, 2015 at 7:16 am #7449
    moeter
    Member

    Some addition: Being in the Home Switch during startup seems to work, if it is configured as home switch only. So the limit switch state confusion seems to start when the limit switches are initialized.

    February 24, 2015 at 7:36 am #7452
    cmcgrath5035
    Moderator

    Something does not seem right here:

    The switches are correctly set to NC, there is a high level on the switches inputs if the axis are inside the working range. Something else that worries me is that if the robot is switched on, and a limit/home switch is activated, the robot can move that axis in any direction, until it moves out of the limit switch. Then the limit switch error is thrown.

    The switch ports on tinyGv8 are pulled high with a resistor.
    If the machine is in the the working area, and the switches are closed (as in NC), then the volatge at the switch should be ground, relative to your tinyG ground reference.
    Only when the machine goes to a limit and operates (opening the NC contact) should the voltage at the switch read high.

    Am I misinterpreting something?

    February 24, 2015 at 8:39 am #7455
    moeter
    Member

    Oh, yes, I’m confusing somehting myself here… Lot’s of input circuitry to get 24V active switches working. Anyways, that was setup correctly as NO. (I am using an elexol opto input board, tinyg is wired to the line transceiver directly they only use to drive the leds…)

    The thing was, the latch backoff values were too small.

    I’m still a bit sad that my suggested fix for this problem hasn’t been built into edge yet. I always have to compile my own version…

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