Another Orac retrofit, re-using spindle encoder?

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thompo
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Joined: Thu 14 Apr , 2022 6:58 am
Hardware/Software: ORAC/Linux CNC

Another Orac retrofit, re-using spindle encoder?

Post by thompo » Tue 19 Apr , 2022 11:27 am

Hi Folks,

Picked up a ORAC of 1985 vintage. appears to be original and unmolested although the monitor did not function so so idea if the computer side works.

I have managed to get the lathe running with the existing PSU, steppers, drives and Jaguar VC150 VFD.
Spindle and axis are running via a cheap breakout board and LinuxCNC and switching the steppers drives using transistor circuit i found here.

I can see the encoder generating the index and reference pulses on the original control board (LEDs on off corresponding with encoder disc).
IS there a way i use this is encoder along with my BOB and LinuxCNC?

Looking through the diagrams for the control board and encoder i have Red as 5v+ and green as 0v. That leaves Blue as speed and Yellow as Sync?
I have wired it like this, taking 5v off my BOB and wiring the signals into the pin 10 & 11 of the BOB.
Setting these pins as spindle signals in linux, does not produce a reading any ideas? Which is index Spd or Sync?

I have included a diagram of the basic setup i have so far.
Orac stepper.jpg
ORac to linuxCNC
Orac stepper.jpg (108.98 KiB) Viewed 5662 times
Thanks for any help

DavidB
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Re: Another Orac retrofit, re-using spindle encoder?

Post by DavidB » Tue 19 Apr , 2022 19:05 pm

I'm afraid I can't help with experience in the Orac conversion as I'm yet to do this myself but you seem to be doing as I intended at least initially and you seem to have the same BOB so it'll be interesting to see how you get on. Regarding the wiring what you have seems to be correct according to the information here http://linuxcnc.org/docs/html/examples/spindle.html see section '6.1. Spindle Synchronized Motion' regarding the required configuration to allow LinuxCNC to interpret the signals as required.

thompo
Posts: 5
Joined: Thu 14 Apr , 2022 6:58 am
Hardware/Software: ORAC/Linux CNC

Re: Another Orac retrofit, re-using spindle encoder?

Post by thompo » Wed 20 Apr , 2022 6:42 am

Done some measuring and found a problem.
5v is provided to BOB by USB and output as 5v on the output sections (steppers/enable etc)
This BOB is taking the 12-24v supply (I have tried 12/18/24v) and providing 9v to the input section.

The encoder produces a +5v pulse when triggered.
I can get Linux to recognise a pulse created by manually touching a wire from 0v to the input pins.

It seems I'll have use something similar to stepper switching circuit to get the 5v pulse to short the 9v to 0v creating the pulses the BOB needs or I bypass the opto isolators on the input and goto the 5v side of the board.

DavidB
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Joined: Tue 19 Oct , 2010 16:06 pm
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Re: Another Orac retrofit, re-using spindle encoder?

Post by DavidB » Wed 20 Apr , 2022 20:43 pm

You may be right about the need for the transistor drive for the inputs to invert the signal and drive the optoisolator, I haven't traced the input circuitry to see how it's wired yet and very little information online about the board circuitry. I think it would be a good idea to drive the original stepper drives through optoisolators to keep the pcgnd and gnd separate. Modern stepper drivers seem to have optoisolated inputs as standard whereas the Parker drives don't AFAIK. I noted that all the gnd are common so the 0-10V is not isolated, that may be fine for some uses but would be a problem when used with the likes of a Triac Sprint drive as the 0-10V input floats at around mains voltage. For my Triac project I have a BOB with an isolated 0-10V circuit for that reason. I haven't found out whether the standard Orac VFD requires an isolated 0-10V signal or not yet or even whether it is 0-10V as the manual I have has some hand written entries for 0-5V and 4-20ma.

thompo
Posts: 5
Joined: Thu 14 Apr , 2022 6:58 am
Hardware/Software: ORAC/Linux CNC

Re: Another Orac retrofit, re-using spindle encoder?

Post by thompo » Thu 05 May , 2022 23:32 pm

Got it all up and running with the standard 48slot encoder.
I had to use the same transistor circuit that is switching the stepper drives to switch the encoder signals.

G33/G76 all working as it should and threads coming out as they should, just need some more tool holders now :D

triac
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Re: Another Orac retrofit, re-using spindle encoder?

Post by triac » Fri 19 Aug , 2022 14:07 pm

Hi
Could you please post some pics of the wiring and connection you finally ended up with to get all working OK ?

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