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  1. #11
    Quote Originally Posted by eurikain View Post
    I could share the job on the same switches, but the relay implies some risky delay (are miliseconds really that risk JAZZ ? That's where I'm not too sure...).
    Not case of being risky. It's case of not being repeatable. The whole point of HOME switches is to be able to repeatabily return to Fixed position every time. The random delay between when switch is triggered and time takes relay to open it's contacts to allow message to control makes repeatabilty impossible.
    The delay for limits isn't so important because like you say it's milliseconds but for repeatabilty purposes that is life time plus it's random amount of time.


    Quote Originally Posted by eurikain View Post
    I'll order three more switches online for the sake of completeness of the machine, but I'll use it without homes until they arrive. Now, can you tell me what kind of switches I should get ? Laser or same type of mechanical switch ?
    Again because of repeatabilty you wan't slightly better switch for homes. Personally I like using inductive Proximity sensors because they are accurate and repeatable. Well more than enough for router anyway.

  2. #12
    I use the LJ12A3-4-Z/BX proximity sensors. You can run them off 24v (10-36v) and the wiring is simple. They are Normally Open switches, so you can put as many as you like with the outputs all connected to one active low input on the BoB. They are specced as 6-36v but don't switch reliably below 10v. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND when Ferrous metal is within 4mm of the sensor head. Again I say, mount the sensor so that the metal passes by it not end on, cause it will get crushed.

    Cheers,

    Rob
    It takes all sorts to make a world, I am just glad I am not one of them.

  3. #13
    Plus one us pensioners have to stick together
    ..Clive

  4. #14
    Quote Originally Posted by Clive S View Post
    Plus one us pensioners have to stick together
    Ye and you stick together in bloody sunshine while us poor buggers freeze to death..

  5. #15
    Quote Originally Posted by JAZZCNC View Post
    Ye and you stick together in bloody sunshine while us poor buggers freeze to death..
    Yes Jazz, it's a lot warmer in the South of Nottingham or the Costa del Stockport than 'Oop North'......
    It takes all sorts to make a world, I am just glad I am not one of them.

  6. #16
    The most economical way is to have one microswitch and one inductive sensor per axis fitted on the moving part. And you mount them so that they pass by their respective adjustable metal stops on both ends.
    Then you wire the sensors in parallel to one BoB input (or to separate inputs if you have them, and you can home all axis simultaneously) and the microswitches in series with the e-stop. You put the limit override to bypass the microswitches loop but not your e-stop.

    In normal operation you will be using only the sensors and only for homing. You will have to set in mach3 the soft limits which will prevent you to hit the limit sensors. In the case you hit the limit sensors you tick in mach3 the automatic limit override and manually back off the respective sensor. Normally the miocroswitches will never be used, only in the worst case scenario if the software is no longer responding or the motor drives are failing, etc., then hitting the microswitch will cut the power to both motors power supply and spindle.

    It is better to have both switches and sensors to operate at 24V. If your BoB do not accept 24V you can either use an optocoupler with a resistor or if the BoB inputs are optoisolated you may change the value of the resistor on the board.

    I noticed you have fuses on your power supplies inputs. You want to have fuses on the outputs to actually protect the power supplies for short circuit, etc. The mains will be protected with one or more circuit beakers. (Eg. one for spindle+motors PSU and one for the 5V+24V PSU)

    Edit: you will also want to wire the alarm outputs from your drive through a relay to the same limits + e-stop relay loop. In this case if one drive gives an error, the other will stop as well. It is also good to have the BoB e-stop input better connected to a mach3 input. This way you can tell mach3 to stop the g-code if the motor power switches off. So you can resume your job quickly.
    Last edited by paulus.v; 24-02-2016 at 12:07 PM.

  7. #17
    Quote Originally Posted by JAZZCNC View Post
    It's case of not being repeatable. [...] The random delay between when switch is triggered and time takes relay to open it's contacts to allow message to control makes repeatabilty impossible.
    Get it :) Sounds obvious now :)


    Quote Originally Posted by cropwell View Post
    I use the LJ12A3-4-Z/BX proximity sensors. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND
    I looked up on AliExpress but not sure I get original ones... where do you get them from ? Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)


    Quote Originally Posted by paulus.v View Post
    You will also want to wire the alarm outputs from your drive through a relay to the same limits + e-stop relay loop. In this case if one drive gives an error, the other will stop as well.
    That's a very important thing you note here, and I will modify my circuit to take drives alarms into account, in fact, last week I made a mistake in Mach3 and while running un-regenerated toolpath and bad configuration, motors stalled, so I almost broke my X axis, because the alarm went off, but obviously was not connected to anything, so X2 kept running... To avoid that in the future I'll wire the alarm outputs as you explained, thought the limits don't belogn to the e-stop circuit. Thanks for the advice :)

  8. #18
    Quote Originally Posted by eurikain View Post
    Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)
    You may connect all your DC 0 volt (GND) lines to ground/earth. There is no problem. Sometimes it helps solve interference issue but most of the time it doesn't really matter if you have them floating or not.

    What is you BoB model?

  9. #19
    Good to know :) My BOB is the typical Chinese Mach3 5 Axis BOB: User Manual of 5Axis Breakout Board - Mach3

  10. #20
    Your inputs have common ground. You can use only PNP sensors. You may use 24V if you wire the input through a resistor of a calculated value. There is no info of the inputs voltage in the manual, but you could find out by reading the resistor values and/or optocoupler model.

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