Midas dc motor conversion

[fieldmouse]

I replaced the ac induction motor on my lathe with a brushed dc motor and a custom controller of my own design. I can achieve control with usable torque over a 100:1 speed range. I use a home built encoder to provide feedback to a PWM control.

I wonder if you think your design is doable for the average bear and if so if you'd want to share a schematic. I like torque.
Mouse

 

[RJSakowski]

I wonder if you think your design is doable for the average bear and if so if you'd want to share a schematic. I like torque.
Mouse

Frankly, it isn't a plug in solution. The concept is rather straightforward. I realized in the development process that low speed torque response is limited by the ability of the control to recognize a need for additional power to overcome a reduction in speed. Variable speed brushed d.c. or universal motors have been used successfully for decades largely because of biofeedback. When the user senses slowdown, he instinctively increases the power via the trigger control. Thus, as a drill bites in and starts to slowdown, more power is added and torque is increased.

My approach was to add an encoder to the control. I took advantage of the intermediate pulley on my lathe which is directly coupled to the motor with a gear belt. The pulley operates at 1/4 the motor speed. I installed 40 small neodymium magnets on the face of the pulley and used a simple Hall effect sensor to measure pulley rpm. The sensor output feeds an analog circuit that creates a voltage proportional to motor speed.

Here is write up describing the process. I also have posted in various threads on the HM forum, many of which nay be found by searching for PWM controller posted by me.

 

[Tincamp67]

Well, I just read the attachment, and half of it was in a foreign language. If I locate a treadmill motor/controls, I will need the elementary school version of the above information.

 

[RJSakowski]

Well, I just read the attachment, and half of it was in a foreign language. If I locate a treadmill motor/controls, I will need the elementary school version of the above information.

Were I, or someone else, to offer a kit, it would be closer to plug & play. A for-sale kit would most likely include a commercial encoder, populated and tested circuit boards, and detailed step by step assembly instructions. Even then, variations of all the different machines would dictate a certain amount of customization. As it is, it isn't ready for prime time and I'm not willing to do the necessary work to make it commercially available.

The important takeaway is that it is possible to attain high torque at very low rpm relative to the maximum rpm of a brushed d.c. motor. The key is the feedback afforded by the encoder. Half the battle in designing a new product is the realization that it is feasible.

 

[Tincamp67]

I’m always game to try something new, I’m just a fish out of water with electronics, and higher math.
A turn key kit would be ideal, but you’re probably right about the variety of potential motors that people can/would acquire and try to use. Too many variables.

Its probably been asked and answered, but why not use the control panel from the treadmill? My working treadmill that I walk on doesn‘t give infinite speed control, but it would give me 10 speeds, with the push of a button. The old one had a slide that gave more of a wide range of speeds. Of course I took that to the scrap bin at the dump 2 years ago, when the tension adjuster broke and the tread shredded. I wasn’t smart enough to strip parts out.

 

[lordbeezer]

Older Treadmills with slide or round speed switch’s are the easy ones to use. They use mc30-40-60 controllers.