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Electrical Questions - DC motor controller

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  • Electrical Questions - DC motor controller

    I recently picked up a LMS Hi-Torque minimill, in great shape- before the PO dropped it on it's back and crushed the motor control box. I bought it as-is, knowing those boards are $100. Well, turns out this one is $273! The motor is 500W brushless, rated at .67 HP.

    So a little research says I can run it with a SCR and a bridge rectifier for under $20.

    I take some off the shelf parts and connect them together to make a low cost treadmill DC motor controller. Parts needed: 4000w or higher SCR motor controll...


    For that matter, a Variac and a bridge rectifier should work as well, n'est pas?.

    So what am I missing?
    What does the OE board do for 10 times the money this does not?

  • #2
    Very possibly (although I do not know this) runs at a particular speed set by the controller.

    probably runs at a more stable speed than the rectifier system will run it at. This may be due to feedback from the motor, which you will not have.

    Likely has much mire stable operation at LOW speeds, where many DC motors have trouble, and many controllers do not work well.

    Try it and see. Try all speeds, under load and running unloaded. If you are happy, you saved money. If not, you know what to do.

    That board that costs $273, might cost all of $40 per each to manufacture in quantity, not something that everyone wants to hear.
    CNC machines only go through the motions.

    Ideas expressed may be mine, or from anyone else in the universe.
    Not responsible for clerical errors. Or those made by lay people either.
    Number formats and units may be chosen at random depending on what day it is.
    I reserve the right to use a number system with any integer base without prior notice.
    Generalizations are understood to be "often" true, but not true in every case.

    Comment


    • #3
      Originally posted by Rex View Post
      I recently picked up a LMS Hi-Torque minimill, in great shape- before the PO dropped it on it's back and crushed the motor control box. I bought it as-is, knowing those boards are $100. Well, turns out this one is $273! The motor is 500W brushless, rated at .67 HP.

      So a little research says I can run it with a SCR and a bridge rectifier for under $20.

      I take some off the shelf parts and connect them together to make a low cost treadmill DC motor controller. Parts needed: 4000w or higher SCR motor controll...


      For that matter, a Variac and a bridge rectifier should work as well, n'est pas?.

      So what am I missing?
      What does the OE board do for 10 times the money this does not?
      Iv'e used a bridge/ variac combo. it was okay. The OE board most likely provides a feedback feature to compensate for load.
      I cut it off twice; it's still too short
      Oregon, USA

      Comment


      • #4
        I thought that a bldc motor needed a ESC driver, similar to what you see at https://www.allaboutcircuits.com/tec...motor-control/.


        A simple circuit with a variac and and rectifier would be suitable for a BRUSHED motor, right?

        Dan
        At the end of the project, there is a profound difference between spare parts and left over parts.

        Location: SF East Bay.

        Comment


        • #5
          Check this website.


          Check out this GoDaddy hosted webpage! http://olduhfguy.com.


          He repairs the mini lathe/mill controllers, and may have one to sell you. His work is excellent, and his prices fair. no commercial interest, just a satisfied customer.

          Comment


          • #6
            Originally posted by chucketn View Post
            Check this website.


            Check out this GoDaddy hosted webpage! http://olduhfguy.com.


            He repairs the mini lathe/mill controllers, and may have one to sell you. His work is excellent, and his prices fair. no commercial interest, just a satisfied customer.
            I have bought a board from him before. He just repairs and returns, typically has no stock even on the plain models. His ebay auction basically says "Don't ask if I have any to sell, they will be posted on ebay if I do". So he can't help me.

            Comment


            • #7
              Originally posted by danlb View Post
              I thought that a bldc motor needed a ESC driver, similar to what you see at https://www.allaboutcircuits.com/tec...motor-control/.


              A simple circuit with a variac and and rectifier would be suitable for a BRUSHED motor, right?
              I just don't know. I'll read up, thanks!


              I read up I'm back to Square One
              Last edited by Rex; 12-03-2018, 08:33 PM.

              Comment


              • #8
                Originally posted by danlb View Post
                I thought that a bldc motor needed a ESC driver, similar to what you see at https://www.allaboutcircuits.com/tec...motor-control/.


                A simple circuit with a variac and and rectifier would be suitable for a BRUSHED motor, right?

                Dan
                That depends in whether the BLDC motor includes the actual sensor and controller inside, or if it is part of this $273 board. The OP seems to have found out that his WILL run from external DC, implying that the basic control is in the motor.

                How many wires come from the motor?

                Some motors include the basic sensor and coil switching, some do not. Ones that DO are controllable over a fairly wide range by the DC level going into them.

                Those that do not, presumably integrate the basic control and the speed control into one external board. the higher cost of this board might reflect that. The number of wires going to the actual motor will reveal what system it has, either integrated basic control, external Hall effect control, or sensorless.

                The sensorless type is rather similar to a vector mode VFD, which has implications if the motor control is that type. The motor is then similar to a PMAC motor (permanent magnet AC motor), which some VFDs can control.
                Last edited by J Tiers; 12-03-2018, 09:07 PM.
                CNC machines only go through the motions.

                Ideas expressed may be mine, or from anyone else in the universe.
                Not responsible for clerical errors. Or those made by lay people either.
                Number formats and units may be chosen at random depending on what day it is.
                I reserve the right to use a number system with any integer base without prior notice.
                Generalizations are understood to be "often" true, but not true in every case.

                Comment


                • #9
                  Originally posted by J Tiers View Post
                  That depends in whether the BLDC motor includes the actual sensor and controller inside, or if it is part of this $273 board. The OP seems to have found out that his WILL run from external DC, implying that the basic control is in the motor.

                  How many wires come from the motor?

                  Some motors include the basic sensor and coil switching, some do not. Ones that DO are controllable over a fairly wide range by the DC level going into them.

                  Those that do not, presumably integrate the basic control and the speed control into one external board. the higher cost of this board might reflect that. The number of wires going to the actual motor will reveal what system it has, either integrated basic control, external Hall effect control, or sensorless.

                  The sensorless type is rather similar to a vector mode VFD, which has implications if the motor control is that type. The motor is then similar to a PMAC motor (permanent magnet AC motor), which some VFDs can control.
                  This motor has 6 or more wires to the controller, all in a single plug.

                  It's looking more and more like the OE is the only route.

                  Comment


                  • #10
                    From the looks of things it's a bit more complicated than the PWM controllers on older Seig machines-

                    HiTorque Mills, Mini (SX2) Replacement Parts 3995 Mini Lathe Motor Controller; Marked XMT-DRV-500C; Rated at 110-120V 50-60Hz; Compatible with SIEG SX...
                    I just need one more tool,just one!

                    Comment


                    • #11
                      The good news is that the guy that fungtn mentioned (http://olduhfguy.com/) will repair the board for $100 and shipping.
                      At the end of the project, there is a profound difference between spare parts and left over parts.

                      Location: SF East Bay.

                      Comment


                      • #12
                        Originally posted by danlb View Post
                        The good news is that the guy that fungtn mentioned (http://olduhfguy.com/) will repair the board for $100 and shipping.
                        The bad news is this board is not repairable. It was dropped off the truck onto the back of the column, wherein the plastic controller box resides. It's cracked in several places.

                        Comment


                        • #13
                          Originally posted by Rex View Post
                          This motor has 6 or more wires to the controller, all in a single plug.

                          It's looking more and more like the OE is the only route.
                          With 6 or more wires, it does appear that you may have the power to the coils, and the hall effect wires coming back, or an equivalent situation. Meaning that DC will not work and you may be stuck with a new board.

                          Do you have a clear pic of the motor with wires and a clear pic of the board? Might be a tie-breaker.

                          The repair option is also potentially good. Assuming that your board has no particular visible damage, no seriously fried parts and/or charred places on the board, it should be repairable by a competent person who knows that board.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment

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