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  • #16

    Re: Variable speed

    Originally posted by al.m.. View Post

    You are absolutely correct about cooling. On the DC motors there is usually one and sometimes 2 fans that help keep the motor cool. However they spin at the same rate as the motor so at low speeds I am not sure that they are effective.

    Nice setup on the drill press by the way
    Rory,
    i have been doing a lot of reading today( home sick). One thing I came across was a thread from here a couple years ago where you said you were going to build a controller out of a 400w scr,a bridge rectifier,and a 5ohm potentiometer.
    How did that work out?
    [/QUOTE]

    I played around with that for a month or so, but could never get something that I was satisfied with. In the end, at that time I concluded that the DC 51controllers were far superior to anything that I could build. Since that time I have discovered that not all DC 51 controllers are created equal. My go to controller is an MC 60 from an old treadmill.

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    • #17

      Re: Variable speed

      Originally posted by tool fan View Post
      Rory,
      i have been doing a lot of reading today( home sick). One thing I came across was a thread from here a couple years ago where you said you were going to build a controller out of a 400w scr,a bridge rectifier,and a 5ohm potentiometer.
      How did that work out?
      I played around with that for a month or so, but could never get something that I was satisfied with. In the end, at that time I concluded that the DC 51controllers were far superior to anything that I could build. Since that time I have discovered that not all DC 51 controllers are created equal. My go to controller is an MC 60 from an old treadmill.[/QUOTE]
      there are numerous free treadmills near me,wish I could narrow down what might have the mc-60 board.
      what spec pot have you found works best?

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      • #18

        Re: Variable speed

        If there are pictures of the controls, look for one that has a dial or a slide to control the speed. Old Weslo's are generally this kind. 10 ohm pots are what I find work well.

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        • #19

          Re: Variable speed

          Originally posted by tool fan View Post
          If there are pictures of the controls, look for one that has a dial or a slide to control the speed. Old Weslo's are generally this kind. 10 ohm pots are what I find work well.
          awsome
          i am suposta pick up a Weslo,with sliding speed control latter in the week.display does not work,but speed control does,free.
          hopfully no one else get there before me

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          • #20

            Re: Variable speed

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            • #21

              Re: Variable speed

              Harvested a functioning mc-60 circuit board and 10 ohm pot out of the second tree treadmill.althogh the motors out of the first and second have the same hp rating the one out of the first has a higher amperage rating and a more usable type foot.just need to adapt a pulley and tidy up the assembly and I have a vintage variable speed lathe

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              • #22

                Re: Variable speed

                I dismantled a Bremshay treadmill that I got for free and studied the motor controller. The controller itself would send power to the motor in discrete steps, incremented or decremented by pulses coming from the main treadmill board. A tachometer (hall effect sensor and magnet) would feed back once per rotation pulses to the main board, and the main board would send up/down pulses to the motor controller in response to varying load conditions, to maintain the set speed. Making a variable speed lathe with this controller would thus involve a control that could send speed up/down pulses. I thought of doing it, with a microcontroller, but ended up going simpler using just a DC motor controller that uses a pot to set the speed.
                Happiness is a new blade!

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                • #23

                  Re: Variable speed

                  Originally posted by guylavoie View Post
                  I dismantled a Bremshay treadmill that I got for free and studied the motor controller. The controller itself would send power to the motor in discrete steps, incremented or decremented by pulses coming from the main treadmill board. A tachometer (hall effect sensor and magnet) would feed back once per rotation pulses to the main board, and the main board would send up/down pulses to the motor controller in response to varying load conditions, to maintain the set speed. Making a variable speed lathe with this controller would thus involve a control that could send speed up/down pulses. I thought of doing it, with a microcontroller, but ended up going simpler using just a DC motor controller that uses a pot to set the speed.
                  Can this be done with a three phase motors Reading the pulse wave modulation and Amps? I know some three phase motors I have a stepper counter on the backside for rotation orientation. I believe this is called sensor vector control. Some VFD’s have sensor less vector control that are only good to the number of poles the motor has. I do not know enough about DC motors, but I do know that they can have a short term burst of torque that AC motors struggle with.
                  For every action there is an equal and opposite reaction.
                  Sir Isaac Newton.

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                  • #24

                    Re: Variable speed

                    This wasn't pulse wave modulation. It was one pulse per step (two inputs, one to step faster, one to step slower). There might have been over 100 steps between zero and full speed. If there was no load (or load variation), then there were no more pulses being sent. The main board simply monitors the tachometer input which sends one pulse per rotation, and nudges the motor controller faster or slower (in reality: more or less power) to maintain the desired speed.
                    Happiness is a new blade!

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                    • #25

                      Re: Variable speed

                      Originally posted by guylavoie View Post
                      This wasn't pulse wave modulation. It was one pulse per step (two inputs, one to step faster, one to step slower). There might have been over 100 steps between zero and full speed. If there was no load (or load variation), then there were no more pulses being sent. The main board simply monitors the tachometer input which sends one pulse per rotation, and nudges the motor controller faster or slower (in reality: more or less power) to maintain the desired speed.
                      I have observed similar responses to loads with less sophisticated mc 60 boards. When a load is applied at low rpm, the motor responds by delivering more power. In this case the hall effect feedback tachometer and magnet that are normally located on the treadmill have been removed. Based upon what you have reported, I have to conclude that something other than the hall effect tach cause the response.

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                      • #26

                        Re: Variable speed

                        In my case, disconnecting the tachometer input would cause the main board to stop the motor and display an error message. This is a failsafe safety issue, not wanting to speed up the treadmill and hurt the treadmill user if for some reason the tachometer was defective.
                        Happiness is a new blade!

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                        • #27

                          Re: Variable speed

                          Originally posted by guylavoie View Post
                          In my case, disconnecting the tachometer input would cause the main board to stop the motor and display an error message. This is a failsafe safety issue, not wanting to speed up the treadmill and hurt the treadmill user if for some reason the tachometer was defective.
                          I have struggled to find a way to use those boards without using the entire control panel, i.e. use the board and a pot to run the motor. Even with the treadmill hall effect sensor and magnet it seems that the motor responds to other sensors and stops. I eventually gave up in favour of the mc 60 boards.

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                          • #28

                            Re: Variable speed

                            Well if it's like the controller board I had on the treadmill (DCMD57) it would be possible to use it with nothing more than two pushbuttons (each one between an input and common) to increase or decrease the speed, but if you have to press it 25 or 30 times each time you turn the lathe back on to get it up to speed, that would get old real quick. A straight DC motor control is much easier.

                            I got this one:

                            https://www.ebay.com/itm/AC-110V-220...IAAOSwlTBdkUGj
                            Happiness is a new blade!

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                            • #29

                              Re: Variable speed

                              I was wondering what controller you were referring to. I tried one of those and while it worked better than the smaller dc 51 controllers the MC 60 from an old treadmill was superior in terms of delivering low speed torque


                              Sent from my iPhone using Tapatalk

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                              • #30

                                Re: Variable speed

                                Originally posted by tool fan View Post
                                I was wondering what controller you were referring to. I tried one of those and while it worked better than the smaller dc 51 controllers the MC 60 from an old treadmill was superior in terms of delivering low speed torque


                                Sent from my iPhone using Tapatalk
                                im going to start with the mc-60 and swe how it works out.
                                while I have your attention,I have a couple ideas about pulleys,going to take some machining ( my brother has a small metal lathe.)
                                what have you done?did you keep the the flywheel? I'm thinking it is needed for cooling

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