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Raspberry Pi Hat Homing Mirror Motor Issue

Discussion in 'Laser Cutters' started by Steven B, Jan 30, 2021.

  1. Steven B

    Steven B New
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    I am currently using the Raspberry Pi CNC Hat (2.6) to drive a 40x40in ACRO Laser etcher (OpenBuilds ACRO 1010 40" x 40") So far it works great! The biggest problem is the Homing of the X-axis which has two motors that mirror each other. When I try to home the device ($H) it is extremely slow but I also notice the motor from the X ports is the only one driving, while it is supposed to be the X and the A (mirrored X motor). I have soldered the back of the hat on the two X solder jumper points. It also seems to work well if I jog the machine with a G00 X__ command or G01.

    I also have already disabled the Z axis in the config.h file of GRBL to be sure it does not try to home the Z first and fail since I only have XY.

    Any suggestions on what to do and how to fix this? Please let me know if there is anything I need to clarify! Thank you!

    Here is a video of what it looks like: Raspberry Pi CNC Hat Issue
     
  2. Steven B

    Steven B New
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    Update: I figured out I blew the Pololu Motor Driver Controller for my A axis. I would love any suggestions on how to prevent this from happening? I am using a 24V 10A power supply, is this too much? It seems everything is within its regulated Voltage/Amps. It does seem to heat up a lot when I am homing the device and sometimes the A motor still cuts out momentarily
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Pololus are about 1/10the capacity you need, so will keep causing issues. They are overly senstive to overheating (the tiny PCB is against the specs of most modern powerpack chips that heatsink into the PCB) and also terribly unprotected against back-EMF and ESD on the motor outputs.

    Consider a BlackBox (4A max drivers, 3.2A RMS. Compared to the barely 0.3A a pololu can give before overheating, and has protected IO all round)
     
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  4. Steven B

    Steven B New
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    Thank you so much! Is there any alternate driver chips you might recommend? I am specifically looking at the raspberry pi hat so I have more programmatic control with the motors and a more compact design. I will explore the black box option, it did not seem I had a lot of programmatic control but looking more into it, it seems it would have an open serial connection I can tap into from the Raspberry pi?
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    Yes, practically the same as the hat, just connects via USB instead of GPIO. Much better solution if we do say so ourselves. See start [OpenBuilds Documentation]
     

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