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  1. #1
    i have a set of three drivers that came out of a syil machine a few years ago. The only thing stopping me from re-using them is the current adjustment...

    They don't have the common switches that most drivers use now, it appears to have an adjustment screw with no means of knowing what current output is set to.

    Anyone have experience with these older stepper drivers and trying to tune what the current output is set to? i want to reduce them to 2A for a set of motors i have on a smaller machine.

    Thanks!

  2. #2
    I've spent 5 minutes Googling - I guess you'll have spent longer, so I won't continue.

    If there's no other clever ideas from the forum, one thing you could consider is this,

    Connect your stepper, wind the pot control to CCW limit. try stepping the motor (if the minimum current is CCW, max CW - which is logic) - it may or may not turn. Rotate the pot CW until the motor is spinning reliably, then leave stepping for 5 minutes, monitoring motor temperature. Continue to rotate the pot bit-by-bit and running the stepper for 5 minutes at a time. I saw a post on here recently by a respected member that suggested a stepper should operate upto an uncomfortable-to-hold temperature (60C, I think was mentioned). If you're running less than this then you can probably afford to up-the-current. What you're looking for is not necessarily 2A, but a safe operating temperature that is neither lifeing the motor or saturating the core. The motor doesn't really care if it has 2.000A or whatever flowing through it - it's looking to generate a magnetic force (proportional to current) without damaging the insulation on the coil through over-temperature.

    Another method would be to replace the stepper with 2 10W, 1R resistors and step the driver until you get maximum potential across one resistor, and read-off the current (I = V, given a 1R resistor) - but that method is fraught with problems if there is a stepped current (positional current and hold current) and/or if the output drive is switched-mode (which I think it is, having seen an internal image on a chinese website) - again, think of the problem space - not to set the current to a specific value, but rather to set the current to keep the motors operating within their thermal range.

  3. #3
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 18 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,320. Received thanks 270 times, giving thanks to others 6 times.
    There probably is some kind of guide to setting the trimpot, but Doddy's first suggestion is probably the simplest and most reliable, short of finding the official guide.

    IIRC modern stepper motors are good to over 80deg, but that's only after several hours of running. If they get too hot to touch in under 30 minutes, or noticeably warming up within a few minutes, I'd be reducing the current, as heating that quickly is a sign you're heading to overheating territory.

    You could wire an ammeter in series with one motor coil, then pulse the step input until the reading peaks, and adjust to set the current. But that's dependant on the driver not having a reduced output mode after a period of inactivity, and the ammeter having enough smoothing to read the average current without being affected by the PWM output. With the motor stationary, and if you know the motor coil voltage rating, you could also do it by measuring the voltage over the coil, but again you'd need enough smoothing to get an accurate reading, but that could be done with an extra resistor and capacitor to create a basic RC filter.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  4. #4
    You ever able to get them to work? If not I'll buy them from you. I probably have the machine it came out of and I can't find any more drivers that are of the same make.

    If you did, can you help me with the pinout so I can stick in another drive for A axis?

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