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Making sense of some power issues...

Discussion in 'General Electronics' started by Marshall Cummings, Nov 5, 2017.

  1. Marshall Cummings


    Apr 15, 2017
    Likes Received:
    Hello everyone,

    I recently started making some connections between the components in my latest build and am running into some issues that have "sparked" a question or two. I don't think these are terribly relevant to what I'm actually asking, but here's what I have;
    • 1 x Pokeys57CNC controller board
    • 5 x HY-DIV268N-5A motor drivers (one spare)
    • 4 x KL23H2100-35-4B stepper motors
    I had just put everything together and wanted to do a simple test or two with the Mach4 software I installed, so here's what I did;
    1. Connected one of the motors to one of the drivers.
    2. Connected that driver to the controller board.
    3. Installed a 5 amp fuse for the installed driver; this should probably eventually be a 3 amp fuse (or 3.5 amp if I can get it, since the motor has a 3.5 amp current), but I thought this would be alright, because...
    4. I set the current on the motor driver to 1.2 amps
    Here's what happened. I started jogging the motor, watching my z-axis move as it should, but as the motor would start, I heard a "bad" sound for the first second or two and then everything sounded normal. I kept moving the motor back and forth, making physical adjustments with wheel tightness, trying to narrow in on the sound. Finally, I suspected the motor itself and not the mechanics, so I removed the motor and jogged it back and forth a few times to confirm. Sure enough, the sound was coming from the motor. As I was jogging the unmounted motor, there was a click and a plume of smoke came from the motor driver! I was one HY-DIV268N-5A driver down!

    Alright, so these things happen. But what I don't understand is exactly why it happened. I think this particular motor is probably bad, but shouldn't the motor controller have limited the current draw to 1.2 amps, thus preventing itself from having cooked? If I had put a proper fuse in place (probably a 1 amp fuse), would that have stopped my driver from going up in smoke?

    I guess, generally speaking, I'm curious about how all of these values should be set. The motor draws up to 3.5 amps, the driver can provide up to 5 amps. I thought this was a good thing - have more available than is necessary. My plan was to choose a fuse based upon the motor current - 3.5 amp motor, 3.5 amp fuse. But everything I read says that fuses are two slow to protect any of the electronics anyway, so why bother?

    Ok, I'll stop there - thanks in advance to anyone who can tell me what went wrong and to how to properly choose these values. Also, my apologies if this sort of information is covered elsewhere - I did a number of searches, but couldn't find anything that really talked about these particular issues.

    Quick follow up - I just noticed that the 5 amp fuse for that controller actually blew as well as the motor driver itself. Not sure if this is good or bad. Anyway, the driver is definitely cooked. Three of the pins of the TB6600 driver chip are good and black and the device no longer powers up.


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