How do I reverse output polarity on PMDX-107 to send -10VDC to KBMG?

[EricMack]

I have a PMDX-107 that I want to connect to my KBIC DC Spindle Control.

(admin note: The subject driver is a KBMG, ignore references to KBIC)

My control wants +0-10VDC for FORWARD and -0-10VDC for REVERSE.

Is there a setting or recommended way to connect the onboard relays to accomplish this?

Normally, if I had a double pole double throw relays I could wire it up so that one position is forward and one reverse. With the PMDX-107 I assume (Hope?) it has a way to do this?

Thank you.

Eric

[Steve Stallings]

The PMDX-107 was designed to operate VFD-like interfaces which use unipolar
0 - 10 inputs.

The actual spindle drive you are working with is a KBMG with a SI6 isolation
board. The KBIC is actually a different model, but the name KBIC has become
like "Kleenex" in that people use it to mean any DC spindle controller, just
like Kleenex has come to mean any type of facial tissue.

It may be possible to rig something up to handle this with a relay. I will think
about it overnight and try to come up with a viable answer.

[EricMack]

Thanks. I'm sure you will think up an elegant solution.

[EricMack]

Hi Steve, while waiting for a response I reread the PMDX and KBIC documentation again -- I did not want to lose the weekend, so I decided to break the problem down into two parts

I hope this will help you help me and others...


Part 1: How to wire a PMDX-107 to my KBIC DC Spindle Motor Controller
For part 1, I just wanted to get the KBIC DC Spindle motor controller to work in forward only. Here's how I accomplished that.

WIRING BETWEEN PMDX-107 and KBIC DC MOTOR CONTROL (Note: I have the SIMG isolation board mounted to KBIC for complete isolation in addition to isolation the PMDX-107 provides)


FROM THE PMDX-126 BOARD TO KBIC
PMDX-126 GROUND  --->> KBIC COM (Common) ground input on the SIMG board.
Note that this common is shared between the E-Stop and the 0-10VDC Signal inputs to the SIMG/KBIC board. Is that OK? Is there a better way?

PMDX-126 E-STOP INPUT (From E-Stop Switch) --->>> also connected to the ENABLE line on the SIMG/KBIC board.
My thinking here was that an E-Stop condition would kill the SIMG/KBOC boards as well as cause the PMDX-107 to stop sending a 0-10VDC signal. Is there a better way?

FROM THE PMDX-107 BOARD TO KBIC
PMDX-107 AOUT ----> SIG (0-10VDC Signal) input on SIMG/KBIC DC Motor Control
I am using the on board 0-10VDC from the PMDX-107 to drive the KBIC control

PMDX-107 A GND ---> Connected to GROUND on SIMG/KBIC (which is ALSO connected to GND on PMDX-126)
I'm concerned about sharing GND as I know that normally the PMDX-107 isolates from the rest of system. The reason I had to tie the ground together is in order to get the ENABLE input on the KBIC drive to work.
I suppose an option would be to just tie the KBIC ENABLE TO ground on the KBIC side and not drive enable from the PMDX-107 at all./ This way, the KBIC is always enabled, relying only on the 0-10VDC to determine when to drive spindle. (That is how it was wired in the AhHa controller days)


OK, so I have read your documentation and described what I have done as best as possible.

The above works but I do not know if that would be the safest or recommended approach, so I am asking for your feedback.


Part 2: How to reverse output polarity on PMDX-107 to send - 10VDC to KBIC? 
Steve, I know you are working on this, so I'll wait. I have given some thought and, since I have a CNC4PC C15 dual relay card, one option may be to use that. Ideally, I was hoping to use only PMDX boards but I am open to using the CNC4PC C15 Dual relay card, driving both relays from the PMDX-107 DIR pin and then using the relays to reverse the 0-10VDC to the KBIC.

Even simpler than the C15 card could be to use a DPDT relay driven from the PMDX-107 that would reverse the 0-10VDX wires. This external relay only energize when I wanted Spindle reverse. Not sure how to best drive it from the PMDX-107, though.

Steve, I know you were thinking of something more elegant when we spoke. I just wanted to put this out there.

Looking forward to your thoughts.

(FYI: I know I've posted several things in the forum today. I took careful notes of my reading and questions. I am posting each separately to make it easier for us and others to track in the future. Thanks for this forum!)

[EricMack]

[This circuit from Steve worked for me. (Thanks Steve) I'm pasting the emails from Steve here so that it can help someone else someday]

Hi Eric,
Well, despite my earlier confidence, I have not come up with a circuit that does not need you to use a relay. That being the case, I have to drop back and recommend a dirt simple one that uses two SPDT relays and a dual op-amp.

Circuit Overview
1. You would control the two relay coils using the Fwd/Run and Rev/Dir outputs from the PMDX-107. The PMDX-107 should be configured for the Run and Direction output mode.
2. The dual op-amp would be powered from the +15 and -15 volts provided by your driver.
3. One op-amp section would be configured as a non-inverting buffer for the Aout of the PMDX-107.
4. The other op-amp section would be configured as an inverting buffer for the Aout.
5. Then the relay controlled by Rev/Dir from the PMDX-107 would select between the outputs for the op-amp sections in order to feed the correct one to the driver.
5. The other relay would control the Enable input to the driver and provide additional isolation.

Schematic attached

Regards,
Steve Stallings
PMDX

[EricMack]

Steve, I've attached a photo of the interface board I built using your schematic. It's not pretty but worked fine the first time I powered up. Thank you!

Some quick comments/questions for you or Bob so I can call this done:
Comments:
- I have removed the SI-6 isolation board from the KBIC, per your instructions.
- I see that we are powering the MC 1458 OP AMP from the +- 15VDC coming from the KBIC. This worked.
- For the relays I used a $3 optoisolated dual relay board from my Arduino kit (see attached). This provides isolation and LEDs to make it easier to see what happening.

QUESTIONS FOR STEVE/BOB:
1. Your schematic appears to show capacitors between COM and -15VDC coming from KBIC Driver. What kind and value should I use?
2. I am powering this circuit from the same 5VDC 1.5 Amp isolated supply that powers my ESS; however to do so, I had to connect COMMON from the ESS to the COMMON on the PMDX-107. It all works but I want to know from you if this is OK or if it will defeat the isolation.

Please advise

[Steve Stallings]

Your board is very bit as pretty as my schematic.  8-)

Yes, the SI-6 should be removed as it does not accept negative voltages,
and it is not needed for isolation since the PMDX-107 is fully isolated.

Yes, the op amp is powered using the +15 and -15 terminals of the KBMG.
Please stop calling this a KBIC because that really is a different animal!!!
You are even getting me saying it. KBIC controllers do not accept negative
voltage input OR have the true Enable input.

As long as you do not connect the COM of the PMDX-107 to anything
other than your relay circuit, everything will be fine. The COM and the
Agnd of the PMDX-107 are isolated from each other.

[EricMack]

Thank you, Steve. I did not realize I was referring to the wrong device.

I now understand that the KMBG is the motor driver and the SI-6 is the isolation board (which I have now removed). Got it. Thanks.

[Steve Stallings]

Edits to call it a KBMG already done.  8-)

[EricMack]

Steve, I'm following up on your comment from earlier today (3 posts above)

ERIC ASKED: "I am powering this circuit from the same 5VDC 1.5 Amp isolated supply that powers my ESS; however to do so, I had to connect COMMON from the ESS to the COMMON on the PMDX-107. It all works but I want to know from you if this is OK or if it will defeat the isolation."

STEVE RESPONDED: "As long as you do not connect the COM of the PMDX-107 to anything other than your relay circuit, everything will be fine. The COM and the Agnd of the PMDX-107 are isolated from each other."

ERIC RESPONDS: Steve, to get power to the relays I have to share the COM from the PMDX-107 with something else, so that would contradict what you advise. Presently,I am powering this circuit from the same 5VDC 1.5 Amp isolated supply that powers my ESS -- which means that COM and +5VDC are shared with my ESS Supply.

Do you advise I add another walwart supply just for the relay side of your circuit? (Even still, that would need to have COM tied to -VDC of the supply)

Does that make sense? I tried to describe as best as I could. Or, is there another way to isolate the power side? (some circuit perhaps?)

[Steve Stallings]

What I was trying to say was that the COM terminal of the PMDX-107 and
the FWD/Run and REV/Dir terminals are a set of signals that are isolated
from all other parts of the PMDX-107.  As long as your power supply, relay
card, and SmoothStepper are wired in such a fashion that no isolation
issues exist, then adding these signals from the PMDX-107 will not cause
and isolation issues.

My understanding is that the relay card has isolated inputs and I would
not expect any problems with your setup.