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ccandiotes
09-23-2017, 03:44 AM
Is it possible to have position read from scales or encoder vs counting steps?

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PlanetCNC
09-23-2017, 04:01 PM
PlanetCNC controller will not read position from scales or encoder. Most modern servo drivers and some stepper drivers will do this. After all, it is drivers "job" to position motors where it was instructed to.

ccandiotes
09-23-2017, 11:54 PM
PlanetCNC controller will not read position from scales or encoder. Most modern servo drivers and some stepper drivers will do this. After all, it is drivers "job" to position motors where it was instructed to.Thank you for the reply. If I use a servo drive, will it read the absolute position value from the PC in some way or does it also count the step&direction pulses and continuously calculate the required steps? Eg the x axis must move from 0 to 10 mm- the control outputs 100 steps- the servo drive counts 100 step pulses and moves the motor 100 "steps" or more until it reads the required position. Some error could creep in due to rounding.

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ger21
09-24-2017, 12:03 AM
A servo drive will move the number of steps it receives, and use the encoder's to make sure it moves to that position.
Whether you send it 100 steps or 10,000 steps, it moves the motor that amount, and uses the encoder to verify that it's at that position. There are no rounding errors.

ccandiotes
09-24-2017, 01:46 AM
Ok, thank you Ger I am eager to add encoders to my existing CNC. Will have to add some circuitry to interface with my encoders and do the positioning.

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ger21
09-24-2017, 07:04 AM
If your existing machine has steppers, adding encoders is very different from a servo drive, which is what I was talking about. I've never used Planet CNC, but I wouldn't expect it to even support adding encoders to steppers?