Digital readout from magnetic or glass scales

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06 Aug 2014 18:52 #49563 by Jake
I searched and searched.....but nothing answered this question.

What about using Lunix CNC to build a DRO. Magnetic or glass scale, I think I will have to build the interface boards as I can not find a board that really takes care of it. I hate to just buy a DRO when I think down the line the mill will get a CNC conversion, But I really do not see ever CNC converting my lathe.

Thanks Guys!

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06 Aug 2014 19:10 #49564 by PCW
If the scales output quadrature, you should be able to read them with
almost any linuxcnc supported hardware including a simple parallel port

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08 Aug 2014 02:48 - 08 Aug 2014 03:10 #49584 by Jake

If the scales output quadrature, you should be able to read them with
almost any linuxcnc supported hardware including a simple parallel port


So it looks like a Mesa 5I21 card will do the trick, I just need to find some scales and build a board to plug the scales into. I think I may end up buying a couple cheap scales to start getting things rolling, as I pretty much dont know what I am doing and starting from the beginning. I do have limited electronics experience. (I am an industrial electrician) I keep thinking about just using an Arduino but this has so much more power to go with it.


ok change of ideas. Since from reading the WIKI the 5i20 is about the standard LinuxCNC card. I think I will get one of those and a 7i47 motion oriented RS422 daughter card to go with it. Then I think the hardware deal should be good to go with 4 scales. Then for writing the programming and I should be good to go. Since both my machines are side by side I think I may setup so I just have all the scales going to one card and just switch back and forth in the software from machine to machine. .......

Thanks !!

Jake
Last edit: 08 Aug 2014 03:10 by Jake. Reason: moment of dumbass

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08 Aug 2014 03:51 #49587 by PCW
LinuxCNC is pretty large overkill for just reading scales

if you do want to use Mesa hardware instead of a parallel port
I would suggest a 5I25/7I85S combination since its a lot cheaper

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08 Aug 2014 17:30 #49594 by BigJohnT
What are the scales for?

JT

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09 Aug 2014 23:28 #49622 by Jake
I am going to have a 4 axis setup on the mill, and a 2 axis on my lathe. I had originally thought of using Linux CNC since I want to CNC my knee mill in the future. Although the prices I have seen lately on older CNC mills it may not be worth starting at square one with a mill that was a manual mill to begin with. Retro a older CNC would be a better route.

I'm not dead set on using mesa hardware I started down that route as there is an abundance of information and support of there hardware. I may build a CNC plasma down the road also. So my thoughts of utilizing components that would help familiarize myself with the system was part of my other thoughts.

For the DRO I'm kinda thinking an Arduino base may be a simpler more cost effective route.

Newbies are a pain in the butt aren't they????

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10 Aug 2014 00:33 #49626 by BigJohnT
www.shumatech.com/web/ offers a cost effective DRO. I have two of the older DRO350's in use on manual machines.

EVERYONE is a newbee at some point! So don't worry about that...

I might suggest using the parallel port to run some steppers, it is a good way to start. My first hurdle was to get EMC to run on a computer back when... then spin a stepper motor from a 5 1/4 floppy drive( I failed at that). Next I got a BOB and ran some Gecko drives and steppers. Now a days I'd start with a 5i25 7i76 for steppers. No need to upgrade as you improve the rest of the system.

JT

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10 Aug 2014 06:10 #49631 by Jake
The Shuma Tech looks like the hot ticket for a somewhat DIY DRO. What are you using for scales? A ton cheaper than a 3 axis Mitutoyo with the inductive scales!


The Shumatech would end up being the same price as the Arduino route by the time I buy the Arduino Mega and the ttl to serial interfaces.



Back to the LinuxCNC route on controls I will have to look into the Mesa setup you referred to.

So if I did want to have a basic input to the computer with linux CNC I would need serial to parallel board then a parallel to pci board correct?

I have some steppers and servo motors around the shop somewhere....

Thanks again Guys!

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10 Aug 2014 18:27 #49650 by BigJohnT

The Shuma Tech looks like the hot ticket for a somewhat DIY DRO. What are you using for scales? A ton cheaper than a 3 axis Mitutoyo with the inductive scales!

The Shumatech would end up being the same price as the Arduino route by the time I buy the Arduino Mega and the ttl to serial interfaces.


I got some cheap Chinese scales from flea bay. I'm sure you would end up with a far better DRO with the Shuma Tech than anything you could roll from the Arduino.

JT

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11 Aug 2014 20:05 #49690 by andypugh
An Arduino and LCD shield ought to work, or you could look at using a Raspberry Pi or BeagleBone running LinuxCNC .
In those cases you would be using general purpose IO, and there is a chance that you might run out of count-rate at high axis speeds. But then how fast can you move an axis on a manual lathe?

FWIW I think having a lathe converted to CNC is massively useful. I rarely use actual G-code, I use pre-written routines like a sort of super-charged power feed.
(Face off to this length at this surface speed, feed and cut, turn to this diameter stopping at that point).

There is a (boring) video here of me making a part that way. I can't imagine going back to manual handle-twiddling.
It is especially useful for threads, you can cut any thread at any pitch at all. My macros are even set up so that I can type "19 tpi" and the box changes to "1.3368" as the lathe is set up in metric.

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