Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake

djstree

@dc42 look forwarward to seeing them. Im eager to use ClearPath servos on my project with a Duet3.

By closed loop do you have input for 1vpp from linear encoders? Or SSI/BissC/1vpp for absolute encoders?

dc42

@djstree said in Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake:

By closed loop do you have input for 1vpp from linear encoders? Or SSI/BissC/1vpp for absolute encoders?

It has a quadrature input that can be used either for a digital linear encoder or for a rotary encoder built into a motor, as well as a separate SPI connector intended for a magnetic encoder that we will produce for attaching to the back of a Nema 17 or Nema 23 motor.

djstree

@dc42 BiSS C-mode would be good to have on the support list too. Open source protocol.
https://www.renishaw.com/media/pdf/en/de4d6a54313b48c3a4dadef7207ac4c1.pdf

"BiSS encoder output with Sin-Cos 1Vpp: BiSS encoders can also provide a 1V p-to-p sin/cos output for real-time control, since the on-demand absolute encoder data can come in too slowly for many control loops."

dc42

@djstree said in Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake:

@dc42 BiSS C-mode would be good to have on the support list too. Open source protocol.
https://www.renishaw.com/media/pdf/en/de4d6a54313b48c3a4dadef7207ac4c1.pdf

"BiSS encoder output with Sin-Cos 1Vpp: BiSS encoders can also provide a 1V p-to-p sin/cos output for real-time control, since the on-demand absolute encoder data can come in too slowly for many control loops."

Stepper motors intended for closed loop control invariably have quadrature outputs. Analog encoder output sounds very retro to me and right now I do not intend to support it. I designed the quadrature decoder on the board to support high data rates, including the data rates provided by Renishaw digital encoders with a resolution of 100 counts/mm at speeds in excess of 1m/sec. This is way faster than the quadrature decoders used in other open source closed loop stepper motor controllers.

I guess analog encoding might be useful for BLDC motor applications where speed is more important than precision.

djstree

@dc42 Thanks for the update! I've just been looking at linear motors / linears scales for a new project requiring 3.2 meter Y travel (moving gantry) on a 1.3m wide granite bed. Tough to decide what to go for IP55 wise.

Mirage

I am definitely keeping a close eye on this new expansion board. My new XY gantry for NEMA23 is ready to take the beating! And clearpaths are in stock

dc42

@Mirage said in Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake:

I am definitely keeping a close eye on this new expansion board. My new XY gantry for NEMA23 is ready to take the beating! And clearpaths are in stock

This expansion board is not intended to drive devices such as ClearPath, because it does the closed-loop control on-board. It's intended for stepper motors with built-in encoders (but no control electronics), or stepper motors with our add-on encoder, or stepper motors driving axes equipped with linear encoders.

Mirage

@dc42 said in Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake:

@Mirage said in Duet 3 NEMA 23 Closed loop with Z axis also using Elec Brake:

I am definitely keeping a close eye on this new expansion board. My new XY gantry for NEMA23 is ready to take the beating! And clearpaths are in stock

This expansion board is not intended to drive devices such as ClearPath, because it does the closed-loop control on-board. It's intended for stepper motors with built-in encoders (but no control electronics), or stepper motors with our add-on encoder, or stepper motors driving axes equipped with linear encoders.

Oh shoot! that's news to me
I was following this thread in the hope of an update soon:
https://forum.duet3d.com/topic/17780/clearpath-servos-with-1xd-expansion

So would taking the Step and Direction signal directly from the header pins of a Duet2 and level shift it to more than 5V be a better solution?

Edit:
Just realized that this thread refers to a completely different expansion board.