Sorry for the delay Ralph.
Been busy.
They are widely available on eBay or Alibaba.
It's the TMCxxxx family of stepper stick drivers.
There are variations amongst the implementations so the two models we recommend are:
TMC2130 for low current motors. They can run hot so heatsinking is desirable.
TMC5160 for higher current motors. Run fairly cool. You would want this one. They're pretty cheap.
Now that the 5160 has finally arrived it's taking over from other drivers we used in the past.
Both can control microstep rates on the fly using SPI.
If you decide to experiment i can find you the link to the github commit file so you can figure out how Howard does it. He's fine with that. Its all open source and should be kept as such, as usual.
Or you can read? the data sheets and work it out that way. Secure in the knowledge it's not a fruitless quest.
Ant?
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On Wed, Jan 29, 2020 at 07:43 AM, Ralph Hulslander wrote:
Ant, do you have a link for " Variable step rates controlled on the fly by SPI are a common feature on drivers currently available."? What drivers? Everything I am seeing are only set by switches when the motor is not turning or powered. I need 3 - 5 amp drivers and would love dynamic? step control.
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Ralph
If I've understood correctly you can beat the 700rpm speed limit by changing from microsteps to full steps? Does it take full steps or could you get away with a low microstep rate such as two or four? Variable step rates controlled on the fly by SPI are a common feature on drivers currently available.
Seems as though gearing for increased tourque is also gearing for increased precision. Obviating the need for microsteps? Obviating the 700rpm limit?
What I find interesting about these new closed loop drivers is that they use a simple diametric disk magnet (North and South are diametrically opposite sides of the disk, not the flat faces of the disk) with a clever sensor chip that measures multiple magnetic field properties to create the equivelant of a 32k line per rev encoder.
Seems like that should be transferable tech. You can buy the driver without the motor now.
The only issue can be getting the diametric disk precisely centred on the end of the motor shaft. Prolly trivial for the skill sets you have.
There is debate how essential this is. The calibration procedure sets things up after all. People claim that when used for 3d printing, the cheaper MKS motor sets, selling for $20, produce a moir¨¦ surface artifact known as salmon skin.
Speculation varies from thinking centering the magnet, PID tuning,? or skimping with a different magnetic sensor chip and? less well filtered circuit are the cause.
The $50 ones from originators, MisfitTech don't appear to have the problem.
They use this sensor chip:
The TLE5012B is a 360¡ã angle sensor that detects the orientation of a magnetic field. This is achieved by measuring sine and cosine angle components with monolithic integrated Giant Magneto Resistance (iGMR) elements. These raw signals (sine and cosine) are digitally processed internally to calculate the angle orientation of the magnetic field (magnet).
I'm not sure it matters in this application anyways but...
Further research while writing this provided a possible cheap fix for the cheaper motors. Eight diodes per motor avoid the moir¨¦ effect. Was for same effect on different driver though.
There are a couple of alternative explanations of why it works in the comments. I'd be interested in any opinions anyone here has on which is the better explanation.
This method appears to provide? high resolution? encoder feedback at trivial cost. Eliminating the need for expensive optical encoder disks and replacing them with a more robust solution.
Looks like the future of servo feedback to me.
Ant?
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Clausing 8520, Craftsman 12x36 Lathe, 4x12 mini lathe, 14" Delta drill press, 40 watt laser, Consew brushless DC motors and a non working 3D printer
