advantages of supplying phase B to spindle encoder

drogge wrote:

Thanks everyone for the input. Looks like I'll be building an simple encoder. If I ever want to do ridge tapping I'll get a real one. Does anyone know of a place to get ABI encoders at a reasonable price? USDigital wants about $120 for theirs.

Drew

Drew, what it is issue with the encoder that _comes_ on the spindle? Is it not good enough? EXAMPLE OF ENCODER

When using JUST phase A, you have a potential to pick up noise pulses as additional counts. When you
use quadrature (A plus there is a filtering effect such that at least some noise pulses can be
disregarded by the encoder counter, making the position reading more reliable. As the
spindle position is cumilative after the synch to index pulse, any error counts will add
up to an incorrect thread pitch.

Jon

Zahnrad, The original encoder doesn't do phase B. Just index and phase A. Phase B is needed for rigid tapping and, as John just pointed out, helps with filtering out noise. Thanks for the info John.

As an aside, a DPO had swapped out the encoder setup with a different opto setup and a disk with just a significantly wider index slot. I assume this is because of the slower software sampling rate of Mach3. Luckily I inherited the original disk and, somewhat butchered up, opto board and I'm in the process of switching back to the original setup, IF I can figure out how to setup pncconf to control the spindle and encoder. It seems you have to enable the right i/o pins in earlier menus to get the spindle/encoder config menus later on.

Drew

Drew,

Ahhhhh.... duh. Now I see. It's an Index pulse and phase A. That's the two reader heads. ( completely talking to myself ) So, a phase B would have another reader head, I presume?

Drew, you'll excuse me and completely understand if I take to riding your coat tails here... Related, I wrote just yesterday, inquiring about how to wire the turret into my 7i77. It's gotten me wondering if there isn't a better way to do these things... replacing the 24V DC motor with something like a stepper or possibly something altogether different.

Thanks for the explanations, folks. Seems I'm learning despite myself.

Yep, that's it. Andy Pugh mentioned adding another read head offset from the phase A. With the correct offset, N+0.25 slots, you can generate phase B. Adding another head to the original EMCO board might be a bit of a chore. Probably wouldn't be too hard to make a replacement board and use the original disk.

WRT the toolchanger, I have one of Andrew Barrow's ECT USB boards and am going to look into what it might take to interface it to linuxcnc. It has the nice feature of sensing the load on the motor when reversing into the pawl instead of just constantly driving the motor at a lower voltage.

What machine do you have? It doesn't look like a stepper would fit very well on my 120 toolchanger.

drogge wrote:

Yep, that's it. Andy Pugh mentioned adding another read head offset from the phase A. With the correct offset, N+0.25 slots, you can generate phase B.

... sigh... Yes, I see that now... Didn't reallly grok it when I read it, before. Now, it makes sense. For some reason, it was not registering with me that the Index pulse used its own, separate head.

drogge wrote:

Adding another head to the original EMCO board might be a bit of a chore. Probably wouldn't be too hard to make a replacement board and use the original disk.

I know nothing of what goes into the boards. Can the readers be bought by themselves? ( ironically, the disk would be ridiculously simple to make )

drogge wrote:

WRT the toolchanger, I have one of Andrew Barrow's ECT USB boards and am going to look into what it might take to interface it to linuxcnc. It has the nice feature of sensing the load on the motor when reversing into the pawl instead of just constantly driving the motor at a lower voltage.

That would be wonderful.

drogge wrote:

What machine do you have? It doesn't look like a stepper would fit very well on my 120 toolchanger.

I've a 220/P. Originally had a bar feeder too. I can pull the covers, but it seems like a stepper should be adaptable enough, in place of the existing motor.

Wow. Easy piecey... So I imagine that the related 'tronics could be mounted just about anywhere out the way, and the trick here is to get the reader mounted in the appropriate place...

Thank you, Andy.

andypugh wrote:

Zahnrad wrote:

So I imagine that the related 'tronics could be mounted just about anywhere out the way,.

Some of those don't need any electronics. Connect them to 0V, 5V and a GPIO pin and they just work.
uk.rs-online.com/web/p/slotted-optical-switches/1273085/ for example.

Oh wow....! I may have to order one just to try that... Ironically, I don't ever foresee needing rigid tapping on this turning center. In fact, I never use it on my turning centers now. But this has gotten my interest from an educational standpoint. Thanks, Andy.