troubleshooting preassembled board

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    I just bought a pre-assembled hobbycnc pro 4 axis board and 4 Nema 23-305 motors.
    I am trying to get signs of life out of the board with a single motor, but failing.
    From replies to other posts, it sounds like the motor should lock when the board is powered on, with nothing connected to the parallel port.
    That is not the case for me. It is just as easy to turn by hand as when powered down.

    I have a single motor connected to the X output.
    The motor wire connections are:
    B = green
    b = white
    Com = brown+orange
    Com = blue+yellow
    a = black
    A = red

    I have a 16V 4.5A power supply connected to TB6. I can confirm that the +5VDC pad is at 5V.
    The 24V fan output is 13.7V, with nothing connected to it.
    All of A/a/B/b are all 16V on the X connector.
    For the Y,Z,A connectors, which have nothing connected, the A/a/B/b are all 0V.

    I couldn’t find a datasheet with a pinout diagram of the SLA7078MR, so I might be numbering them wrong, but viewing the board from the bottom with the row of 12 pins called the “top” and the row of 11 pins called the “bottom”, calling the top right pin 1, counting left up to 12 across the top, and then counting from 13 up to 23 from right to left on the bottom, the voltages are as follows:
    1 = 16
    2 = 16
    3 = 0
    4 = 0
    5 = 0
    6 = 0
    7 = 16
    8 = 0
    9 = 5
    10 = 0
    11 = 16
    12 = 16
    13 = 16
    14 = 16
    15 = 0
    16 = 5
    17 = 5
    18 = 0
    19 = 5
    20 =5
    21 = 5
    22 =16
    23 = 16

    I have not found anywhere that documents the waveforms needed on the input pins, but my guess was that it steps in the direction determined by the direction pin every time the step pin cycles (on upward transitions perhaps?) I tried setting the direction pin to 0 or 3.3V, and cycling the step pin between 0 and 3.3V, but nothing happens. From parallel port diagrams I found elsewhere, it looks like the X direction pin 2 and x step pin 3 should be the second and third from the right, on the top row of the parallel connector on the board. Is that right? Is 3.3V high enough to count as HIGH?


    Let’s see if we can get you up-and-running!
    Your stepper wiring is correct (per FAQ Stepper Motor Wiring and Dimensions.

    A power supply of 16V 4.5A is quite lower than I’d like. Each motor will draw up to 3 amps, and the “rule of thumb” is the higher the supply voltage, the better. For this board and these motors, I’d recommend 36 Volts DC at 10 amps. Nevertheless, you should get SOMETHING with the supply you’re using.

    The datasheet for the chip can be found here: SLA7078MR datasheet. I’ve never bothered to measure any output voltages on the chip.

    Your understanding of step and direction is accurate.

    Vin high is specified at .75 of VDD. 5V * .75 = 3.75V. I’m guessing your fine.

    I just updated the FAQ on no motor movement to include “verify voltage at testpoints”.

    There are two things that will make the motor move freely when power is applied:

    1. No microstepping jumpers. See FAQ microstepping configuration
    2. The motor current settings (voltages controlled by the blue trim pots) is set to zero volts. I try to set them to zero before I ship the board. See FAQ Checking Voltages

    Please give me an update on these two things.

    Thanks, BrianV



    The issue wass the blue trim posts. The voltage there was zero, but turning them resulted in the motor being activated.
    The link you posted mentions a manual. I did not receive one. Was I supposed to?




    Yeah, about the manual. YES, there should have been one in the box.

    If it’s OK with you, you can download one from here: 4 axis PRO Assembly Instructions

    Glad you’ve got motors turning.

    I need to include some text that the motor current is set to zero.



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