7i96 with analog Spindle Servo

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15 Nov 2025 18:37 #338464 by gravedigger
7i96 with analog Spindle Servo was created by gravedigger
How can I connect an analog servo controller to the Mesa 7i96s?
DA+ to TB2-24
DA- to TB2-22
GA GND to TB2-23
I want to control the direction of rotation via + and -. Therefore, I only need S (spindle) ON connected to, for example, TB3-16.
The Mesa only outputs 5V, so do I need to adjust the parameters in the servo controller?One more question about the 7i73 board. How do I activate Mode 3 for the analog inputs for potentiometers? 

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15 Nov 2025 19:23 #338465 by PCW
Replied by PCW on topic 7i96 with analog Spindle Servo
The 7I96S analog output is designed for unipolar use and will not work
wired directly to the drives analog inputs. It's possible to do this but requires
external +- power supplies.

Since the drive has step/dir inputs, I would use those instead

 

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15 Nov 2025 22:40 #338474 by gravedigger
Replied by gravedigger on topic 7i96 with analog Spindle Servo
I think `step/dir` is causing problems.

The incremental encoder has 2500 lines and therefore 10000 pulses. The motor needs 10000 pulses per revolution at 6000 RPM.

That's probably too many.

I need to somehow change the pulses via the parameters. But I'm stuck for ideas.

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15 Nov 2025 22:43 #338475 by gravedigger
Replied by gravedigger on topic 7i96 with analog Spindle Servo
 

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15 Nov 2025 22:49 #338476 by gravedigger
Replied by gravedigger on topic 7i96 with analog Spindle Servo
Or should I switch to unipolar with CW and CCW?
What is the simplest and safest option?

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15 Nov 2025 23:03 #338478 by PCW
Replied by PCW on topic 7i96 with analog Spindle Servo
Step/dir at 10000 steps/turn and 6000 RPM (1 MHz step rate) in not an issue for the 7I96S
but it would require a step pulse length < 0.5 usec. Not sure if the drive will work with that.
(the manual seems to lack timing specs) You can change the steps per turn scaling to make this
easier.


You could also use analog in unipolar mode (0 to +10V  plus a direction signal)
This would require an external 10V power supply (12V would be OK with the proper hal setup)

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