Arduino resolver to encoder conversion

dave4 wrote:

Hello all, read Andy's interesting Arduino conversion project in wiki Linux, I'm doing a first up LinuxCNC retrofit with Mesa cards 5I25 & 7I77 to replace an NC on its way out. Thought I was onto a winner with the Mesa 7I49 resolver card but the existing 400hz, 26V - 11.6V resolvers are way out of spec..

The 7i49 provides excitation as well as reading the feedback. Resolvers themselves are voltage-agnostic, I am sure that they would work at the voltage output of the 7i49.
I would be a little more concerned about the excitation frequency, but it might well be that the resolvers would work perfectly at the 2.5kHz output by the 7i49.

Do you have a specification for the actual resolvers?

Note that the 7i49 is a 50-pin interface card and might not work with the 5i25. It might be possible to use the HD-DB ADAPT board (store.mesanet.com/index.php?route=produc...74_80&product_id=285) but I think that if you were to use the 7i49 then a 5i24 PCI card would be a better fit. Most of the 7i77 functionality is duplicated by the 7i49 anyway.

To answer the question....

The Arduino convertor was a fun experiment. I would not consider using it for a motion control axis, the resolution is too low and the jitter is too high.
It might be possible to improve the software by adding a DPLL, but it might just introduce further problems.

My machine now uses a 7i49 and there is not really any comparison.

dave4 wrote:

Thanks very much for the feedback! Since writing I decided to make life simple and follow the Mesa 5I25 and 7I77 path and use encoders

Resolvers are better than encoders in many ways. It seems like a retrograde step to swap them out. I accept that it might be easier in some cases, but 5i24 + 7i49 is pretty much as easy to set up as 5i25+ 7i77.

Is there a better input location thanks on either of the 2 Mesa cards for the control panel pb's? eg cycle start, feed hold, single block, coolant override and the feedrate pot. I generally watch the workpiece and work those controls by touch, only using a pendant on setup. regards ...

I am not sure I quite understand the question. Are you talking about physical location or electrical location?

For control panel and pendant interfacing the 7i73 can be a very neat solution. You need a smart-serial channel. On my machine I use 5i23 + 7i49 then have a 7i44 on the second header of the 5i23 that has my drives, GPIO and a 7i73 attached. The 7i77 board has a single channel of smart-serial for one device, but more can be added on the second header of the 5i25.

The 7i73 can drive a remote LCD panel, which might suit you.
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