Steppers motor start moving without any commads being given

More
13 Mar 2025 07:54 - 13 Mar 2025 07:54 #323806 by sameedansar
We have built a CNC machine using open-loop stepper motors. The motor drivers are connected to a computer via a breakout board, which is linked using a DB25 cable. Most of the wiring is done using jumper wires, and we have a common ground for all electronic components. The Y-axis is driven by two stepper motors, one for each arm.To improve signal stability, we have added pull-down resistors to each Step- pin of the motor drivers. However, we have observed that the potential difference between the 5V pin and ground pin of the breakout board (powered by an 18V power supply) is only 1.6V. Additionally, when the Y-axis motor stops working, the potential difference between the 5V pin and the Y-axis direction pin drops to 0.06V.Thus, we suspect that the breakout board is damaged. The 5V pin on the breakout board should provide a stable 5V, but since it only outputs 1.6V, the board’s voltage regulator or power circuit may be faulty. The fact that the Y-axis direction pin drops to 0.06V when the motor stops further suggests a power issue or weak signal.Additionally, we suspect that electrical noise is affecting system stability, leading to random motor movements. Interestingly, noise issues only appear when the PC is connected to the breakout board. What could be the reason for the issue? Should we also connect breakout board with a usb cable to the PC for extra power. YOU can view our breakout board specifications in the file attached below. 
Attachments:
Last edit: 13 Mar 2025 07:54 by sameedansar.

Please Log in or Create an account to join the conversation.

More
13 Mar 2025 13:51 #323835 by atrex77
Try to measure potential difference bethween the pc ground and stepper drivers ground, if this card not have optical isolation on the step-dir signals, its cause problems.

Please Log in or Create an account to join the conversation.

  • tommylight
  • tommylight's Avatar
  • Away
  • Moderator
  • Moderator
More
13 Mar 2025 13:57 #323839 by tommylight
Upload pictures of wiring here on the forum so we can have a look.

Please Log in or Create an account to join the conversation.

More
13 Mar 2025 15:50 - 13 Mar 2025 16:45 #323847 by PCW
AFAIK those breakouts do not have a 5V regulator, you must supply 5V.
So the behavior you see is pretty much as expected. That is, the 5V side is being
powered (weakly) via the PC parallel port data pins.

The regulator just supplies the inputs and the analog spindle interface
(regulates to 12V)
Last edit: 13 Mar 2025 16:45 by PCW.

Please Log in or Create an account to join the conversation.

Time to create page: 0.340 seconds
Powered by Kunena Forum