Smoked my spindle - likely my fault

Okay, so maybe I am over my head, but I thought I had this one figured out, but I was wrong.  I followed the suggestions from several posts, including [url=https://162.243.45.186/27-driver-boards/48095-cannot-make-pwm-work-on-mesa-7i96s

Edit: I am not sure what I did, but much of my original message is missing; I have tried to recreate the just of the message below:

Okay, so maybe I am over my head, but I thought I had this one figured out, but I was wrong.  I followed the suggestions from several posts, including [url=https://162.243.45.186/27-driver-boards/48095-cannot-make-pwm-work-on-mesa-7i96s

With my old GRBL controller, I used a PWM-to-voltage module to run my Spindle, an AMB 1400 FME-P DI .  The module generated 0-10v while being supplied with 24v.  I thought the 7i96s Analog Spindle Interface would replace this module.

The only power I have in the new controller is +-5v, +12v, and +48v.  Based on my interpretation of setting hm2_7i96s.0.pwmgen.00.offset-mode to TRUE, it would allow me to supply -5v to SPIN- and +5v to SPIN+ and then shift the voltage on SPIN_OUT to 0-10v.

So, I wired it up and tested it with a DVM; the voltages looked fine, at least for the speeds I tested.  So, I decided to hook up the Spindle.  I ran "m3 s3500", and the Spindle started; I cannot verify the speed, but it seemed correct.  Next, I tried "ms s10000"; the Spindle sped up, and it, too, seemed fine.  So, I decided to try "m3 s18000", (the speed I use most often), the Spindle sped up, but based on the pitch of the noise from the Spindle I think it was running at a higher speed.  I was reaching for the eStop when the Spindle went crazy, speeding up, and then there was the terrible burnt electronics smell.  My hand was over the eStop, so it only lasted a second.  I am afraid even to try to start it, fearing the worst.

As I mentioned, I used a PWM-to-voltage module previously and thought it would be safest to return to it.  The 2-PWM bit file uses STEP/DIR 4, which is my A-axis.  I did read a post about a person using software-driven PWM on an output pin, but they were using a 7i96, not a 7i96s, and it was unclear, at least to me, how they had wired it.  I would guess they wired OUT+ to PWM+ and GND to PWM—but that is only a guess.

I am at a loss as to what to try next.

Any help or suggestions would be greatly appreciated.

I am not sure whether to scrap the idea of using the Analog Spindle Interface or try to figure out software-driven PWN and return to the PWM-to-voltage module.

Looking at my INI file, I see pnfconf reset my OUTPUT_SCALE = 25263, but I had it set as OUTPUT_SCALE = 1 before the test.

Output scale should be set to the maximum RPM of the spindle

I am pretty sure I never typed 25263 into pnfconf. Since the spindle's maximum RPM is 25000, I will reset OUTPUT_SCALE. I think I may have set it to that value at one point, but I have made so many changes that I am losing track.

I am not sure why the spindle went crazy, all I can think is the voltage went too high.

The output voltage is limited to the SPIN+ voltage supplied to the 7I96S
(at 100% PWM meaning the commanded RPM= OUTPUT_SCALE the
output voltage will be the SPIN+ voltage, at a commanded RPM of 0
the output voltage will be 0V relative to SPIN-)

As I mentioned, I have SPIN+ fed +5v and SPIN- fed -5V; that was the only way I could get the 10v range. I understood that setting hm2_7i96s.0.pwmgen.00.offset-mode to true would give me the 0-10v the spindle expects.

I guess there is the risk that the supplied ±5v could vary somewhat; I'm unsure how to protect against that. But at s18000, the voltage should have been well within the 0-10v range.

For 0 to 10V, you would not use offset mode

If you wanted -5V to +5V (and you had +5V and -5V supplies)
you would connect SPIN- to -5V, SPIN+ to +5V and use offset mode.

Also note in offset mode with +5V and -5V supplied, the output voltage
will be at -5V when PWM is disabled so a separate spindle enable is a necessity.


The output voltage cannot go below the SPIN- voltage
or above SPIN+ voltage regardless of any settings.
 

Now, I am more confused. I need a 10v range; the only power I have available at the 7i96s is ±5v and ±12v. The spindle has a 3-wire connection, Power Supply (10-26 VDC), Ground (0 VDC), and Speed Control (0-10 VDC). The Power Supply connection is connected to +12 VDC, the Ground connection goes to the control box Gnd (signal and chassis), and the Speed Control is connected to SPIN_OUT. Since I do not have a 10v supply, I am providing ±5v; my understanding was I needed offset mode to move the -5 to +5v range to 0 to 10v range.

Is that not correct?

If you use -5V and +5V supply you have -5 to 5V control, not 0-10V. With that you have 10V range yes, but the lower end is at -5V, not 0.
Remember that with only 3 wires (supply, ground, speed) the 0-10V speed is measured against ground.
You have to use separate 10V supply for the control.

Test with SPIN+ = 5V, SPIN- = gnd. The spindle should turn with half speed if it survived the negative voltage.

It's also good to tell the maker/model/etc of the spindle, it helps to undestand how it should be controlled.

The title is also highly misleading, if the spindle controller died it's caused by the negative voltage applied and is actually a connection problem. Not caused by mesa card.