John -

Here is a description of an enclosure for the US Digital Strips and
read heads. It came from a Machining mailing list CAD_CAM_EDM_DRO
on egroups.com. The author of the note was Dan Mauch. Also, here is a
link to a picture of the enclosure, mounted on a milling machine.

http://www.metalworking.com/dropbox/_1998_retired_files/DROXencoder.jpg
http://www.metalworking.com/dropbox/_1998_retired_files/DROX1encoder.jpg

"I will try and find some picurrees of my enclosed US digital linear
strips.
Essentially,  it is a 1X2 rectangular aluminum tubing. I made end caps
that
are inserted into the ends of the tubing and serve as a seal, a mounting
flange and a location stop.
The linear strip was mounted onto a pieces of 1/4" square aluminum stock
with 2 mill double sided tape. The strip is so light and with the
rigidity
of the mylar there has been no problems with this technique after one
year
of operation. The 1/4 stock with linear strip is epoxied into the 1X2
housing on one edge . Whereas there is no phyical contact with the
encoder
strip epoxy is an easy way of securing the strip to the housing
The encoder head is mounted on a polypropylene slider that positions the
encoder head to run over the linear strip. The slider is moved by a
piece of
5/16"D aluminum tubing that serves as a cable conduit and as a push rod
for
the slider. The endcap on one side has a hole bored to allow the 5/16
pushrod to line up with the slider .
I think a picture of my encoder set up is in www.metalworking.com in the
drop box under droxencoder.jpg
    Dan"

Mike Gann

John wrote:
>
> Hello PIC.ers,         (longish post)
>
> After years of dealing with quad. optical rotary encoders and the counting
> circuitry associated with them, I have only come across very few makers
> of the linear variety.
>
> HP make the HEDS9200 encoder, and you use their matching code strip to get
> resolution as fine as 360 counts/inch.
> USDigital offer the same device & it is easier to obtain their's
> than HP's.
> (HP is represented heavily in SA, USDigital isn't...   go figure..  )
> Also, USD have been promptly very helpful to me but I'll still be left with
> an incomplete answer - has anyone out there in PICland ever put one of
> these devices into a 'plunger - type' housing, or seen it done?
> I need to end up with an assembly with a spring-loaded (or maybe gravity)
> plunger sticking out the bottom as mechanical dial gauges have.
>
> The HEDS parts usually do duty in apps. where the opto. and code strip
> are mounted on separate mechanical components which are themselves
> confined to move in very restricted ranges, e.g. milling machine slides,
> printer carriages, etc. with good lateral stability.
>
> The sensor WILL be used in a PIC app. (16f877 or 16c74) for measurement
> and control of a hydraulic press doing tests on granular load-bearing
> material, to derive stress-strain relationships.
> The closed loop controller (16c74 based, made in this shop) for the machine
> already exists, but an appropriate displacement sensor doesn't.
> If a HEDS-based sensor can be made to work, it will be massively cheaper
> (ratio 1:5 or so) than the other established displacement transducers
> like LVDTs, capacitive plungers or non-contact optics.
> These have generally better resolution, but that's overkill in these jobs.
> Afterwards, I'll have a bunch of other related apps. which have been crying
> out for this for many years.
>
> Comments anyone? Suppliers? Alternatives?
> If JS Controls started _making_  these as a new business line,
> would folks out there like to buy them from me?
>
> TIA & bestos,   John
>
> e-mail from the desk of John Sanderson, JS Controls.
> Snailmail:          PO Box 1887, Boksburg 1460, Rep. of South Africa.
> Tel/fax:            Johannesburg  893 4154
> Cellphone no:   082 469 0446
> email:                jsand@pixie.co.za
> Manufacturer & purveyor of laboratory force testing apparatus, and related
> products and services.