Re: DRO card and future projects

If you use the linear encoders like I did then you will have zero backlash
on the display. I email you a seperate picture of my us digital encoder set
up.
Dan
-----Original Message-----
From: Steve Gunsel <gunsel@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: Saturday, May 22, 1999 7:58 AM
Subject: Re: [CAD_CAM_EDM_DRO] DRO card and future projects

>From: Steve Gunsel <gunsel@...>
>
>Tom,
>
>I am definitely interested. I noticed that US Digital also offers
>linear encoders for $2 per inch, which sounds reasonable. Of course
>the electronic "readers" are extra, but the cost should be about the
>same as for as a rotary (I presume!). Wouldn't this help address
>backlash? At least you should be able to tell where you actually are.
>I'm not sure how the slop effect when changing directions - not likely
>to be good. But wouldn't this be a problem even with backlash
>compensation?
>
>Steve
>
>At 10:02 PM 5/21/99 -0700, you wrote:
>>From: Tom Kulaga <tkulaga@...>
>>
>>I guess you've all seen the posts about the DRO card I built. I've
>>got an update to the software, adding metric support, cleaning up a
>>few things I didn't like, and changing the 4th axis to display in
>>degrees instead of linear units. I haven't posted it to the webpage
>>yet because I wanted to add backlash compensation first. That's the
>>problem.
>>
>>The big drawback of backlash compensation is that you are forced to
>>make sure that all of the slop is cranked to one side of the travel
>>before you can zero that axis. If you don't, the computer doesn't
>>know where you are inside the backlash zone, and you can't trust the
>>numbers on the display.
>>
>>My question is this: Do those of you who want to use rotary encoders
>>have a problem with this? Keep in mind, you won't be able to zero
>>the axis until you are certain that you've moved all the way to the
>>left or the right of the slop. I can think of more than one occasion
>>where this would be *really* annoying, but usually it would just be a
>>matter of getting in the habit of watching what you're doing a bit
>>more so than normal.
>>
>>So, did I get that across clear enough? Is it worth it to add this
>>feature? I don't want to spend a whole bunch of time working on a
>>feature that nobody will want to use, especially since I've got a new
>>project I want to start.
>>
>>Speaking of that new project, I've been following the comments about
>>the EMC software (gotta love the free stuff ;) with interest, and got
>>to thinking about how I'd go about trying it out here at home. I was
>>thinking that buying a motion control card is pretty pricey, and that
>>my DRO card makes a great jumping-off point for bigger and better
>>things. With a little extra work, and probably an extra 200 bucks, I
>>could come up with a 3-axis servo controller card design. It's a
>>little more involved, but using PWM for the output signal cleans it up
>>nicely, bringing it into the 'definately doable' range, even for
>>beginners.
>>
>>I think that this group could easily write plans to build the card,
>>the servo amps, and the guidance you'd need to assemble the lot into
>>a really good webpage. I can handle the card OK, but I need to know
>>how the card interfaces with the EMC stuff, or if I could provide all
>>the register-level programming info to somebody who could write a
>>driver or whatever is needed to get things going. I don't yet have
>>Linux here at home, so I can't really experiment much. If there's
>>interest in this, I'll order Redhat next month.
>>
>>What do you say, guys? Sound like fun?
>>
>>-Tom Kulaga
>>
>>
>>
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