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Topics - spumco

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Dear PMDX,

I have inductive proximity sensors I'm connecting to a PMDX-126.  The cables are too short and I've purchased some 3-conductor foil-shielded cable to extend the run to the 126.

Question - the original cables are not shielded.  How would you suggest terminating the shielding (there's a drain wire available) on the cable extensions?  The easiest way appears to be installing a screw terminal on the enclosure backplane adjacent to the 126 board and connecting the drain wire from the various sensors to this (new) earth terminal.

Or - leave it floating and don't worry about the shielding?

Or - connect all the drain wires to a conductor and terminate the conductor at some other ground point?  Such as the star ground block inside the enclosure (adds about 10"-12" from the proposed backplane terminal location).

Or - is there some location on the 126 that is suitable for connecting the shield drain?  I suspect not, but figured I'd ask.

Thanks,
Spumco
Thanks

2
Having a problem as I go through the process of designing the control system on a 4-axis mill (retrofit).  As I'm sure you're used to hearing - I'm a novice at this stuff so electronic terms may go sailing over my head.

Current hiccup is that I'm trying to get the spindle encoder signal to both my VFD and the control software.  The VFD needs feedback for low-speed accuracy and improved torque, and the software needs it to do rigid tapping (via electronic gearing between spindle and Z-axis motor).  I'd like - but don't need - to send an index signal to the software as well in case I fit a tool changer that has to be homed.

The WJ200 VFD accepts a 2-channel single-ended signal (A, B, GND).  The A-terminal can be 5-24Vdc, but the B-terminal must be 24Vdc only.

The software and motion controller (UCCNC/UC400ETH) can monitor 2 pins for a spindle encoder signal (A, B), as well as an index signal.

My spindle motor encoder is a BEI quadrature with index (A+, A_, B+, B_, Z+, Z_) and operates at 5-24Vdc.

Other inputs (not including estop, resets, enables, etc):
3/ea NPN-NC homing (10-30Vdc)
1/ea NPN-NC limits (6/ea 10-30Vdc, series)
1/ea 24Vdc VFD alarm signal
2/ea touch probes (future)

Although I already have a two-port BOB, it is restricted to 5Vdc only inputs.  This is going to be enough of a hassle to attach the 24Vdc inputs that I'm happy to spend money on a PMDX BOB that makes wiring/integrating easier.

It appears that a PMDX 126 plus a 108 input board will provide me with the inputs I need/want for current and future expansion, as well as making the wiring easier for homing/limits.  If not, please let me know. 

Spindle control will be via a 106 board I bought from you a couple months ago based on a plan to try to integrate the OEM control hardware with the VFD.  That plan has been abandoned, but the 106 appears to be the ticket for spindle 0-10Vdc control and I have it in hand.  I don't see a need to buy a 107 (or something else) if the 106 will do.

My questions
1. How do I split the quadrature signal from the encoder to both the VFD and the 126/108, and is there some reason I shouldn't do this?  I don't think any small timing difference between the two signals will cause issues as the VFD and UCCNC shouldn't be competing.

2. Can the 105 translator board take the quadrature signal and change it to single-ended?  It appears that this is the case, but I'm trying to double-check to compensate for my total lack of experience with this stuff.

3. Assuming that splitting the signal isn't a bad idea, should I split the quadrature signal, or split the single-ended signal?  i.e. two 105 boards and some sort of splitter upstream, or one 105 and a single-ended signal splitter? My guess is that the less single-ended wiring I have, the less chance of noise interference and placing the 105(s) as close to the VFD and 108 is preferred.

[The VFD and low-voltage hardware are in different enclosures, so there will be 24"-36" of cable from the encoder termination (105 or splitter) in the low-voltage enclosure to the VFD.]

4. I'd like to keep as much in the control system at 24Vdc as possible.  Can the 108 take a 24Vdc input (presumably from the 105) rather than me trying to figure out how to drop it to 5Vdc? Or does the 105 drop the outputs down to 5Vdc? In which case, how do I maintain the 24Vdc signal to the VFD?

Enough for now.  Thank you in advance for any assistance you can give me with this.

Regards,
Spumco

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