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Thread: Dynamotion > Mach3 Defining Axes

  1. #21
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    Default Re: Dynamotion > Mach3 Defining Axes

    Quote Originally Posted by TomKerekes View Post
    Hi toolbag33,

    I don't understand what you are asking.


    First get your limits properly interfaced to some inputs and check out hat they are working using the digital IO Screen.

    Regards
    So I have J7 pins 0-7 to Normally closed limit switchs, from j7 5v back to the 0-7 pins. And I dont see where the copy to c program sets them as inputs.



  2. #22
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    Default Re: Dynamotion > Mach3 Defining Axes

    Hi toolbag33,

    I assume you meant to say bit numbers and not pins.

    Please avoid switching input pins directly to +5V. Even though it shouldn't cause damage it should be avoided.

    When the switch opens it will leave the pin unconnected and floating so it will be in an indeterminate state. A pull up or down resistor is needed.

    You might consider using the first 8 inputs on JP4 or JP6 which have pull down resistors and switch them to 3.3V

    KFLOP IO default to being inputs. There is no need to configure them as inputs.

    Regards

    Regards
    TK http://dynomotion.com


  3. #23
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    Default Re: Dynamotion > Mach3 Defining Axes

    Quote Originally Posted by TomKerekes View Post
    Hi toolbag33,

    I assume you meant to say bit numbers and not pins.

    Please avoid switching input pins directly to +5V. Even though it shouldn't cause damage it should be avoided.

    When the switch opens it will leave the pin unconnected and floating so it will be in an indeterminate state. A pull up or down resistor is needed.

    You might consider using the first 8 inputs on JP4 or JP6 which have pull down resistors and switch them to 3.3V

    KFLOP IO default to being inputs. There is no need to configure them as inputs.

    Regards
    Are the inputs on the KFLOP sinking or sourcing?



  4. #24
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    Default Re: Dynamotion > Mach3 Defining Axes

    Hi toolbag33,

    I'm not sure what you mean. Normally outputs are described as being able to sink or source (or both) current. I suppose you mean to say should they be connected to sinking or sourcing outputs?

    KFLOP inputs are very high impedance (many meg ohms) mosfet voltage sensitive inputs. They must be actively driven high (>2.0V) and actively driven low (<0.4V).

    That is why a pull down or pull up resistor is required when interfacing with a simple switch. Otherwise when the switch is open nothing will be actively driving the input and the pin may float to any random voltage depending on parasitic capacitance to other signals or leakage currents.

    HTH
    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: Dynamotion > Mach3 Defining Axes

    Actively driven as in current from the 5 volt source to the input when the switch is closed, and pulled low with a resistor when open. J7 inputs have internal resistors.

    Sent from my SM-G900V using Tapatalk



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    Default Re: Dynamotion > Mach3 Defining Axes

    Hi toolbag33,

    I'm having difficulty understanding.

    I already recommended to not switch 5V directly to any KFLOP inputs. Are you still doing this?

    JP7 does not have any pull down resistors. Have you added some?

    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: Dynamotion > Mach3 Defining Axes

    Quote Originally Posted by TomKerekes View Post
    Hi toolbag33,

    I'm having difficulty understanding.

    I already recommended to not switch 5V directly to any KFLOP inputs. Are you still doing this?

    JP7 does not have any pull down resistors. Have you added some?

    Regards
    Then how do I drive the inputs high?

    Sent from my SM-G900V using Tapatalk



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    Default Re: Dynamotion > Mach3 Defining Axes

    Tom Kerekes,
    If you not going to answer my questions in a correct and helpful way, just don't Post anything!

    Sent from my SM-G900V using Tapatalk



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    Default Re: Dynamotion > Mach3 Defining Axes

    There's got to be a ground in there some where right? So 5v to switch, to input, to ground. Current flow when the switch is closed, driving the input high. 10k ohm between the switch and ground to drive input low when switch is open.

    Sent from my SM-G900V using Tapatalk



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    Default Re: Dynamotion > Mach3 Defining Axes

    ToolBag, what you are proposing would work, however as Tom has already said, it's not ideal to connect the inputs directly to 5V.

    What would be better is if your switches are at 5V, is connect a 10K resistor between the KFlop input pin and 0V, then wire a 5K resistor in series between the switch and input pin. That way when the switch is open, the 10K resistor pulls the input to 0V, but when the switch is closed and the 5V connected via the 5K resistor, the two resistors act as a voltage divider, so the input pin sees 3.3V.

    I've used those values as an example, however I'd probably use lower values, as the 15k at 5V, means only 0.33mA of current flows, which could make things susceptible to noise. I'd personally aim for at least 5mA of current flowing, which means using a total resistance of just 1000ohm. But that would mean using 330ohm and 770ohm resistor, which might not be that common (without looking at a catalogue, I'm not sure if those are common values or not!). The key thing is to aim for the 2:1 ratio between the resistors, so you still get around 3.3V.



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    Default Re: Dynamotion > Mach3 Defining Axes

    M_C,
    This is just getting better! I ran chose to use j4 which have the pull down resistors when the switch is open, and ran 3.3 volts to one side of of all my limits and the other to the inputs, on j4 and it cooked my board! Godaamnit! Even though the manual said these were 3.3 volt tolerant, when I plug my board in no more lights. Oh well. I'm sure I did something wrong. But how? Did I need a ground on the input side as well?

    Thanks



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