Seeking advice on converting machine to either Mach or LinuxCNC

[Jim Dawson]

I'm not sure if AF is the answer. It seems that it may not be possible to to directly connect a sin/cos encoder directly to a 18x0 card. So far I have not been able to find any information on anyone actually doing this. Somewhere I saw something about different firmware that would allow the connection, but so far I can't find it. Contacting Galil might be useful.

You might want to take a look at this application note http://galil.com/download/application-note/note1248.pdf I doesn't really apply to the DMC-1830, but some good information.

Here is some additional information for a DMC-17x0, this would also apply to a DMC-18x0 sine encoders | Galil

[BMcCaskill]

I took this section of the DMC-17x0/18x0 manual as saying that it would accept analog encoder feedback without needing any additional hardware.

DMC-1700/1800

The DMC-1700/1800 accepts feedback from either a rotary or linear encoder. Typical encoders provide two channels in quadrature,
known as CHA and CHB. This type of encoder is known as a quadrature encoder. Quadrature encoders may be
either single-ended (CHA and CHB) or differential (CHA, CHA-, CHB, CHB-). The controller decodes either type
into quadrature states or four times the number of cycles. Encoders may also have a third channel (or index) for
synchronization. The DMC-1700/1800 can also interface to encoders with pulse and direction signals. Refer to the “CE” command in
the command reference for details. There is no limit on encoder line density; however, the input frequency to the controller must not exceed 3,000,000
full encoder cycles/second (12,000,000 quadrature counts/sec). For example, if the encoder line density is 10,000
cycles per inch, the maximum speed is 300 inches/second. If higher encoder frequency is required, please consult
the factory. The standard encoder voltage level is TTL (0-5v), however, voltage levels up to 12 Volts are acceptable. (If using
differential signals, 12 Volts can be input directly to the DMC-1700/1800. Single-ended 12 Volt signals require a
bias voltage input to the complementary inputs).
The DMC-1700/1800 can accept analog feedback (+/-10v) instead of an encoder for any axis.
For more information see the command AF in the command reference.

That being said, if adding one of the analog I/O boards makes things easier and isn't too costly, I'm all for it. I've bookmarked about a dozen application notes, so I have a LOT of reading to do tonight! This is almost like being in school again!

[Jim Dawson]

I'm learning right along with you. This is interesting

[BMcCaskill]

I posted this on the Galil forum this morning.

Using 12 ?A analog differential encoders w/ a DMC-18x0 (DMC-1830) | Galil

[BMcCaskill]

Well, after a couple days of reading (the post you linked here in particular), you are definitely right that it can't be done without the extra interpolation hardware. Now I need to figure out which will be more economical, buy the Galil converter or replace the encoders with their digital equivalents.

[PCW_MESA]

Well, after a couple days of reading (the post you linked here in particular), you are definitely right that it can't be done without the extra interpolation hardware. Now I need to figure out which will be more economical, buy the Galil converter or replace the encoders with their digital equivalents.

You might take a look at Heidenhain EXE boxes on Ebay.
These often go for around $50 (cheapest are typically EXE602s which do 5X interpolation max EXE610s do 10X, 660s do 400X!)

[BMcCaskill]

Double posted

[BMcCaskill]

You might take a look at Heidenhain EXE boxes on Ebay.
These often go for around $50 (cheapest are typically EXE602s which do 5X interpolation max EXE610s do 10X, 660s do 400X!)

Thanks for mentioning those. I was wondering if they were compatible or not. Excuse my ignorance, but does the input current rating have to match exactly (12μA encoder w/ 11μA converter) and what are the advantages/disadvantages to lower/higher input frequencies (5x vs.10x etc.)?

[PCW_MESA]

The input current does not have to match exactly (the EXE box spec is 7 to 16 uA PP)
Higher interpolation factors give you better resolution but may limit your maximum speed
(the pdf EXE6XX manuals are available just do a google search to get full specs)

[Jim Dawson]

The EXE box is interesting, never seen those before. Another option might be to replace the read heads, here is an option I am looking at for new installations.

MSR50H linear magnetic encoder (readhead),1/2.5/5/25 um,Good,like RENISHAW LM10 | eBay

These are supposed to be compatible with the Renishaw LM10 read heads. I have had some conversations with the manufacturer and got them to make some product changes. I have not tested them yet, but plan to, compared to the LM10s on my machines. They should work with the standard 2mm magnetic tape.

[BMcCaskill]

The EXE box is interesting, never seen those before. Another option might be to replace the read heads, here is an option I am looking at for new installations.

Well, I just ordered 3 EXE 650B X25/10'S so I'll keep you posted on how they work out.