Connecting a glass linear scale to linuxcnc

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12 Dec 2018 12:08 #122262 by jools
Hi All

I want to make a compensation file as my ball screws have minor errors in them along their length so have some questions about which to buy, how to connect them and how to connect them to the Halscope to log values.

This is the one I'm thinking of buying Linear glass scale and I would just like confirmation that it's easy to hook up. It doesn't say it has a quadrature output that I've read is easy to hook up but the output numbers and letters match one on ebay that defines the output as quadrature. Does anyone know if this is compatible? If not can I be pointed in the right direction.

When I get them are they a simple connection to my BOB? I have a Leadshine MX3660 with 3 spare inputs ( MX3660 manual ) so does anyone know if it just connects up or does it need power (I have a DC power supply). If anyone has a basic wiring diagram that would really help me.

On halscope I have read into it and will play with it once I have the encoder hooked up but if anyone has guidance to the selections / parameters / inputs to speed up that process then I would be grateful.

Thanks in advance.

Jools

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12 Dec 2018 13:01 #122263 by jools
UPDATE
So I found the installation manual and I can navigate the installation and wiring with the exception of knowing what the 'R' input is on the attachment??

I'll update once I have the scale.

Jools
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12 Dec 2018 14:25 #122267 by tommylight
Parallel port can be used for VERY slow movement, not for anything usable, and as far as i can tell, those are serial communication not encoder outputs. TTL and RS422 are serial.
Mesa boards have RS422 interface namely the 5i25 or 6i25 with a 7i74 would probably do, but that has to be confirmed by PCW .

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12 Dec 2018 14:29 #122268 by Todd Zuercher
Most likely an index signal.

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12 Dec 2018 14:32 - 12 Dec 2018 14:36 #122269 by Todd Zuercher

tommylight wrote: Parallel port can be used for VERY slow movement, not for anything usable, and as far as i can tell, those are serial communication not encoder outputs. TTL and RS422 are serial.
Mesa boards have RS422 interface namely the 5i25 or 6i25 with a 7i74 would probably do, but that has to be confirmed by PCW .


They are not serial, RS422 means that it's a differential signal. (not necessarily a serial com.) And a parallel port is TTL. (TTL means single ended 5v signal.)

PS: You probably can read them with a parallel port. But the maximum speed you can read them at reliably may be a limiting factor. What that speed is will depend on their resolution and your base thread speed.
Last edit: 12 Dec 2018 14:36 by Todd Zuercher.
The following user(s) said Thank You: tommylight

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12 Dec 2018 15:01 #122271 by Hakan
R is most likely Index signal. On my linear scales there are index dignals every 50.000 mm. 1 um resolution is better, but depends on what you need. Means more pulses/second and lower top speed. Ttl signal level is what you need.

If it is only for creating a compensation file it is probably ok, there is no hurry.

I use mine for active feedback control and need to travel faster and generate more pulses than a BOB can handle. They are sino ka300/1 um/ttl.

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12 Dec 2018 15:03 - 12 Dec 2018 15:04 #122272 by jools

Todd Zuercher wrote:

tommylight wrote: Parallel port can be used for VERY slow movement, not for anything usable, and as far as i can tell, those are serial communication not encoder outputs. TTL and RS422 are serial.
Mesa boards have RS422 interface namely the 5i25 or 6i25 with a 7i74 would probably do, but that has to be confirmed by PCW .


They are not serial, RS422 means that it's a differential signal. (not necessarily a serial com.) And a parallel port is TTL. (TTL means single ended 5v signal.)

PS: You probably can read them with a parallel port. But the maximum speed you can read them at reliably may be a limiting factor. What that speed is will depend on their resolution and your base thread speed.


My base thread is about 3600 (or is that my latency on base thread)

I only want it connected to make a compensation file so the movements don't have to be fast and it will literally be used on each axis twice to take the measurements of expected coordinates v's real coordinates. Do you think it will be ok for that?
Last edit: 12 Dec 2018 15:04 by jools.

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12 Dec 2018 18:40 #122292 by Todd Zuercher
In that case, if you are only using it for calibration, and will not rely on it for production (removing it). It should not matter if it is slow.

3600 is most likely your latency and is quite good. I would think you'd might able to run a 10000ns on that, if the PC is fast enough that it doesn't bog down user-space too much. (I'd have a hard time believing any pc could run a base thread that fast.)

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12 Dec 2018 18:52 #122293 by PCW
Beware that the MX3660 inputs are OPTO coupled and liable to be very slow
If you want to read the scale via a parallel port you may want a second port without OPTOs

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12 Dec 2018 19:13 #122295 by jools

PCW wrote: Beware that the MX3660 inputs are OPTO coupled and liable to be very slow
If you want to read the scale via a parallel port you may want a second port without OPTOs


Hmm maybe on this I'm not too bothered as I can run it very slow as it's just for the comp file.

I was however thinking of using the MX3660 inputs for a spindle encoder. Do you think they'll cope with speed, direction and impulse for that? I was just going to use a home made photo interrupter style rotational disc; do you think it would cope with that?

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