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Thread: Are resisters needed?

  1. #1
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    Default Are resisters needed?

    Hello,
    Thank you for taking a look.
    I have a 5x10 router running mdrive steppers on x and y. They work great, the drivers are married to the motors and are super simple to set up/wire.

    I'm installing a new standard type nema23 on the z axis. It has the normal separate driver. I need help figuring if it needs to be wired with resistors and if so their values.

    I'm going to run this stepper:
    Manufacturer Part Number: 23HS45-4204S
    Motor Type: Bipolar Stepper
    Step Angle: 1.8 deg
    Holding Torque: 3.0Nm(425oz.in)
    Rated Current/phase: 4.2A
    Voltage: 3.78V
    Phase Resistance: 0.9ohms
    Inductance: 3.8mH ± 20%(1KHz)

    and this driver

    Input Voltage: DC24V~60V
    Continuous Current: 7.5A
    Max Pulse Frequency: 200K
    Default Communication Rate: 57.6kbps
    Overcurrent Protection: Peak 10A±10%
    Over voitage Protection: Peak 90VDC

    with his power supply:
    48V/7.3A Switching CNC Power Supply (KL-350-48)

    I'm running step and direction only, no enable

    I'm thinking I need a resistor on PUL+ and DIR+ ?? I have spent a few sessions/hours on the interwebs searching for specific info. Any help is much appreciated!!
    Any help in figuring the values would be great if this system needs a resistor.
    Thanks Again
    Vince

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  2. #2
    Member Jim Dawson's Avatar
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    Default Re: Are resisters needed?

    Assuming your controller outputs a standard 5 VDC signal for the step & direction, no resistor should be required.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Are resisters needed?

    Thanks Jim-
    It says 5V. I'm just on the other side of town in Hillsboro, small world.
    Thanks Again,
    Vince



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    Default Re: Are resisters needed?

    All the stepper drivers I have looked at that have opto-isolated step . direction & enable inputs

    are designed to work with 5V logic level inputs and have a resistor of around 200 to 300 ohms to limit the LED current to about 16 to 10 mA


    the enable input is the odd one out as its a negative logic input that may be better seen as a disable input !

    the stepper driver being enabled with no signal in to the enable input !!!



    first stepper driver found on line has this

    Are resisters needed?-dm542t-input-resistors-jpg


    if you assume the volt drop across the LED is 1.8V

    with a 5V input
    the internal 270 ohm resistor limits the current to 3.2 / 270 = 11.8 mA

    with a 12 V input
    the 270 ohm + 1000 ohm resistors limits the current to 10.2 / 1270 = 8 mA

    with a 24V input
    the 270 ohm + 2000 ohm resistor limits the current to 22.2 / 2270 = 9.7 mA


    John

    Last edited by john-100; 12-10-2019 at 10:02 AM. Reason: correct typo


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    Default Re: Are resisters needed?

    John,
    Thanks for clarifying

    so with a 48V power source
    46/3270 = 14 mA??

    3000 ohm resistor if such a thing is made??

    Vince



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    Default Re: Are resisters needed?

    Would it be safe to say that:
    .014x48 gives me .672 watts?
    I found a 1.5k, 1 watt resistor, so run 2 in parallel?
    I think I may be getting now???
    Vince



  7. #7
    Member Jim Dawson's Avatar
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    Default Re: Are resisters needed?

    Vince, you are confusing the motor power (48V) with the signal power. Your controller should output 5V step & direction signals, that is industry standard. The step & direction signals are not connected to the motor power supply in any way.

    Jim Dawson
    Sandy, Oregon, USA


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    Member john-100's Avatar
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    Default Re: Are resisters needed?

    which breakout board or motion control are you using

    I expect your board to operate at 5V TTL levels so you don't need any resistors


    most breakout boards either have an onboard regulator to drop stepper driver supply to 5V or are powered by an external 5V supply
    on some Chinese BOB's uses the 5V from a PC's USB port

    this Chinese BOB for example
    Are resisters needed?-ebay-cnc-bob-jpg
    takes 5V from the PC USB port to power the IC's that connect the PC to the stepper drivers

    and has a 10V regulator that drops the 24V that very often powers a TB6560 stepper driver
    to power a PWM to analogue 10V converter and the opto-isolators used to connect the 5 inputs to the PC

    the only control I can think of of hand that uses 24V for inputs and outputs are industrial programmable logic controllers

    the Gecko G540 has a built in regulator to drop the 15 to 50V supply to 12V for its logic circuits
    so you will find the open circuit voltage at one of its 4 inputs
    ( the 5th input is used by the G540 to signal a E-stop or fault )

    John



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    Default Re: Are resisters needed?

    John,
    100% understood , and thank you for taking your time to explain. The break out board or controller is definitely 5v. Routing parts as we speak. Thanks again!
    Happy holiday-
    Vince



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