[Jim Blackwood]

Just trying to understand what's going on here.
I have a 600 P/R dual channel optical encoder.
I have an AMC B25A20ACQ amp
I have a Galil DMC 2160 controller.
I have servo motors with the optical encoders mounted.

Is there some reason why this setup will not work together?
Galil accepts optical encoder feedback so my intention was to connect those there.

Do the amps have to have feedback also to work?

I have not seen any combination of optical encoders with hall effect sensors combined. Don't they do the same thing? Why would the amps also need feedback? It seems redundant.

Given the choice of either controller feedback or amp feedback, why would one be a better choice than the other?

Next question:

What exactly is being accomplished with commutation? Is this just a fancy way of saying that the controller knows what kind of motor it is driving and has some sort of a positional reference, or is there more to it than that?

If the type of motor is accounted for in the PID adjustments, is a two channel optical encoder sufficient to give the controller the required positional reference?

Thanks for being so helpful, you guys are the best!

Jim

[Al_The_Man]

Number 1, the hall effect sensors, or the now more common, hall tracks on an encoder, is used to commutate a BLDC motor.
With Galil you do not need any feedback to the drive, apart from hall inputs, the encoder itself is returned to Galil to close the loop, preferably set the drive to torque mode.
The controller, or trajectory planner, Galil, is much preferable.
Mach uses the drive closed loop, which is inferior to the Galil approach.
I have used Galil for many years now, and it is the closest thing to an Industrial CNC controller.
Al.

[Jim Blackwood]

Thanks Al, I think that was what you and others were telling me quite some time ago when I first went looking for the Galil controller, following what still looks like very good advice.

So now the trick is to put the pieces together.

Do I understand you to say that, with a BLDC motor the encoder goes back to the Galil controller and I still need hall sensors going to the AMC servo amp in order to commutate the drive? (That is what it sounds like to me.)
If that is the case, what is the simplest way to add the Hall sensors? Do I start over and look for an encoder which has a Hall effect commutation track built in? (Got any hot leads?)
Or is there a way to add the hall sensors to the motors? (Possibly spacing the encoders out somehow) btw, ebay really comes up blank on a search for "hall encoder".

Obviously you know how to do this, I just seem to be missing some critical pieces of understanding in order to visualize it.

Jim

[Al_The_Man]

I am assuming you have BLDC motor, so are you saying they do not presently have any kind of hall effect or equivalent encoder tracks?
If not, then you can add them with an encoder that has the equivalent tracks, but they have to be installed and phased with the stator windings, which can be done with a double beam scope.
Also they have to be matched to the pole count of the motor.
What is the model of the motors you have?
Al.

[Jim Blackwood]

Thank you. Yes, BLDC motors and no, no Hall effects. Just a simple double channel encoder. The motor is a PacSci R34SENT-TS-NS-NV-02 on which the original tachsyn was removed and replaced with the 600 P/R optical encoder. Greg has a scope and has mapped out the motor. I believe it is a standard 3 phase motor but will have to ask him how many poles it has. Perhaps there is a spec sheet on the motor somewhere.

Am I correct in thinking the Hall effect sensors have to be configured to match the motor? Same number of poles and such?

That is on the quill and potentially the rotary table later as well. On the table x and y axis I have Parker Compumotor ZX610 servomotors which have a built in resolver and I have added on the optical encoder. They are currently being driven by Parker ZX servo controllers but those are single axis controllers and are not capable of coordinated motion, hence the need to change over to the Galil. They are also not capable of accepting an analog input, hence the AMC servo amps.

If I understand what you are telling me, these encoders I have will not work. (Another $60 and 4 weeks down the drain, and at this point the 4 weeks are the larger concern.)

So where can I get the correct encoders?

Thanks greatly.
Jim

[Al_The_Man]

Whether through-hole or shaft type, You should be able to get the encoders from Renco, USdigital, Toyo etc.
If you short the stator leads and turn the shaft, you will feel as series of 'Bumps' count how many/turn and this is the number of poles.
The method I use to align the encoder is to connect a 10k resistor to each phase and connect all three resistor ends together, this will be your scope common for one channel, connect the 'scope to the A phase.
Place the other scope channel to the Hall A output, and Back feed the motor at around 100-200rpm and turn the encoder until the hall aligns with the generated A phase.
The PDF shows the signals.
Al.

[Jim Blackwood]

OK, so the Hall is aligned with the winding so that it is in phase. Makes sense, the amp will then look for the Hall before sending a pulse to the winding apparently.

The motors appear to be 4 pole. Checked cogging with 2 leads shorted, checked with 10K resistors and analog VOM (2 positive pulses, 2 negative pulses). So clearly the Halls have to match that, so 2 pulses per revolution then, 3 phases.

My current encoders are shaft type 6mm dia and face mount. Anything you know of at anywhere close to a reasonable price that will do the job? I can modify the mounts but I already have the spiral couplers.

Thanks again,
Jim

[Al_The_Man]

For anything close and cost effective you may want to check Toyo, although I have not used them for some time so I don't know what they currently offer for commutation encoders.
I believe Automation Direct carry them.
I used to use Renco, but since Heidenhain took them over their stock is not that great and the prices are up there now.
Also check US digital.
Al.

[Jim Blackwood]

Well, they have encoders that are apparently identical to the ones I have now except that they have an index output (A,B and Z). Does that work? I suppose it would tell the Galil controller where the armature is, but I don't know how the amp would know.
http://www.automationdirect.com/stat.../encoderld.pdf

Jim

[Al_The_Man]

You need 5v line driver differential output encoders, I use the marker as a zero reference same as done in commercial systems using the Galil home routine and home L.S.'s.
The axis travels at jog speed until it hits the zero L.S. it then goes into slow until it sees the once/rev Z marker, this is registered as Home.
The encoders you need also have to have 4 pole motor commutation (hall) tracks.
Al.

[Jim Blackwood]

Thanks Al, I think maybe that covers everything except the index gating (US Digital) A/B High or A/B low?
The 600 P/R with quadrature gives 2400/.200" of travel. What would be your recommendation? If I'm going to have to spend $135 each on these I might as well optimize my choices.
I'm unsure how the shaft mounting on these works. I'd really rather have something more like the ones I now have mounted but so far haven't found any.

Jim

[Al_The_Man]

I use 1000p/rev as a minimum.
The 5v differential output A & B and the complement, /A & /B this gives you the optimum against noise issues and is compatible with Galil.
Al.

[Jim Blackwood]

Thanks Al.
OK just to review then I need optical encoders with a commutation track and preferably also with an index output. The desired outputs then would be A, A/, B, B/, Z, Z/, plus U, U/, V, V/, W, W/.
The commutation track would be for a 4 pole motor.
The encoder track would be 1000 P/R.
Preferred mounting would be face mount and if possible 3ea 3mm on 14mm BC although drilling other patterns would not constitute a hardship.
A 6mm shaft is required.
A small form factor is preferred.

If I've made any omissions, errors or incorrect assumptions please tell me.

Now the obvious task is to find encoders that match as nearly as possible those requirements. I would prefer to avoid units that require an additional $25 pigtail if at all possible, but if that is the only limitation it can go.

So far I've found the form factor without the commutation track, and the commutation track in a strange and questionable package. So any more specific pointers would really be a big help.
Are you familiar with EPC? (Encoder Products Co.) Their model 15S looks interesting...

Jim

[Al_The_Man]

The outputs look OK, the halls will go to the drive and the encoder to Galil, using Galil to supply the +5v, you only need the common and halls to the drive, the +5v drive supply will remain open.
Many of the AMC etc drives do not require the U/,V/,/W, so these complements do not need to be fed to the drive.
Many makes just show the motor pole count by the electrical revolutions the motor makes per one mechanical rev, e.g. Renco would be 1000/4 for a 1k pulse 8 pole motor.
So ensure the right halls are specified.
I have used EPC in the past, but not for BLDC as yet.
Al.

[Jim Blackwood]

Yeah... EPC runs about $195 each so I'm looking for a lower priced alternative, although we did get all the way through their part number menu up to output type when the tech guy bailed on me and told me the price:
OC Open Collector
PP Push-Pull
HV Line Driver
PU Pull-Up Resistor8
OD Open Collector with
Differential Outputs

I'm guessing this is open collector with differential outputs maybe? The tech guy kind of freaked when I suggested just hooking up the A and B outputs instead of A, B, C, A/, B/, and C/.

So anyway, what do you think about the capacitive encoders like CUI? Seems like the cost is in the ballpark and they look pretty flexible as far as configuration:
404 Error - Page Not Found | CUI Inc

Mounting would take a little more work but I can handle that easily enough I think, just make some stubs to mount them on if I need to.

And finally, do you think I should be considering 2000 P/R for a .0001 resolution or finer? (.200"/turn leadscrew, 1:1 belt drive) I guess the Galil will have some sort of limits.

Sorry for all the questions and being pretty ignorant about this stuff. I'm usually not a slow learner but I am very much afraid of missing something and having to start all over. Again.
As before, I really do appreciate the help.

Jim

[Al_The_Man]

If hooking up to Galil you need differential A /A B /B Z /Z etc, it was only the halls that I meant to hook up the 3 only and not the complements.
Although Galil will take single ended, there is no point if ordering new.
The encoder frequency response of Galil is up to 12Mhz I have used 5k count encoders with no issue.
I tested the CUI BLDC encoders and was disappointed, also they could not give any support, the guy who designed them was no longer there or somesuch!

[Jim Blackwood]

Well, that's a little less than a glowing endorsement. So I guess I have to keep looking. I'm really supposed to get these ordered this week. Right now I don't know how I'm going to be able to do it. About half what EPC wants is my price point but so far that one is the only thing that looks like it will do the job.

Any other suggestions, or do you think that's going to be as good as I can do?

You are correct, I looked at the Galil man2100.pdf file again and it does input both sides of the encoder. Not sure how I got that confused but I'm glad you caught it.

Jim

[mike_Kilroy]

you dont want 'open collector" with or without line driver..... you want simply "line driver" output (you say HV). We sell EPC. there are other models that may be less expensive than the 15S. If you want to list the full part no of what you picked so far and describe any mechanical give you will take compared to it, I and maybe others would be happy to look and give you more options.....

I just looked back at page 1 of this thread and see you asked for spec sheet on the pac sci r34 motor; we are distributor for that too; if you send me an email with the full part no I will be happy to send you the spec sheet (it shows the pole count too).

[Jim Blackwood]

Thanks Mike The EPC P/N I came up with is 15S-20-M1-4000-A-5-R-HV-M06 (accepting your recommendation). So that's:
15S series
6mm shaft
3 hole 28mm BC mount (can change this)
4000 P/R (probably anything between 2000 and 5000)
4 pole
5 volt
A&B Quadrature with Index
Line Driver
6 meter cable (can change this)

Any help is greatly appreciated.
The PacSci is an R34SENT-TS-NS-NV-02 (round body) The Tachsyn has been removed to mount the encoder to gain compatibility with the Galil.
My email is Jim at BlackwoodLabs.com
It'd be great to have that spec sheet but confirming that it is a 4 pole motor (can't see that it could be anything else) might be the most important thing.

Jim

[Jim Blackwood]

This is killing me, there's got to be another option.
EPC wants $255 each. That's for P/N: 15S-20-M1-40000A-5-R-HV-M06. With a lead time of nearly 2 weeks with shipping.
Yet as I understand it, all I really need is a set of 3 Hall sensors that each turn on and off twice per revolution.

Is it true that for motor manufacture it is common practice to place the hall sensors in the motor windings themselves and use the PM rotor to activate them? Obviously done this way the rotational position of the hall sensors in relation to the windings is sort of important, but how hard can that be? After all, I do have full machining capabilities including a dividing head. Windings do have a distinct positive physical location after all.

Sorry to be such a cheapskate but $1000+ is just a little out of my budget right now, and I'm also under time constraints.

Jim