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'[EE]:DRO using old PC mouse'
2001\08\01@162533 by nickomalley

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Hi,

I would like to build a Digital Readout (DRO) for a minilathe, and was
thinking of using the slotted wheel inside an old mouse with the IR led and
photo transistor. Couple the slotted wheel to the lathe saddle and couple it
somehow to the bed of the lathe.

The question is what sort of resolution can I expect to achieve using this
set-up.

I was thinking of counting the pulses generated when the wheel spins, using
a PIC and sending the result out via RS232 to a computer where further
calculation can be carried out, and the result displayed.

Do you think this is feasable or will it be to innacurate. I was hoping to
measure to 1000th of Inch.

Your thoughts would be greatly appreciated.

Best Regards

Nick

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2001\08\02@044651 by Sergi Sanchez

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face
> I would like to build a Digital Readout (DRO) for a minilathe, and was
> thinking of using the slotted wheel inside an old mouse with
> the IR led and
> photo transistor. Couple the slotted wheel to the lathe
> saddle and couple it
> somehow to the bed of the lathe.
>
> The question is what sort of resolution can I expect to
> achieve using this
> set-up.

As high as you want. You get as pulses for turn as slots has the wheel, so
you can mechanicaly multiply the saddle displacement and measure it with the
wheel.

> I was thinking of counting the pulses generated when the
> wheel spins, using
> a PIC and sending the result out via RS232 to a computer where further
> calculation can be carried out, and the result displayed.

See Microchip's AN520 "Implementing a Simple Serial Mouse Controller" locate
in http://www.microchip.com/10/appnote/category/16c5x/00519/index.htm for
ideas.

...mmmmm but I could be ambitious... think on add a LCD for direct readout.

Sergi. (sorry for my english)

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2001\08\02@185619 by Peter L. Peres

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> resolution

The resolution can be pretty good. A normal mouse has 24 to 48 slots
(varies) and a mechanical multiplication ratio of x 10 or so. The real
resolution is near 100 dpi with the original ball & axle. If you drive the
axle directly you just count the slots and arrange for one rotation to
satisfy your resolution requirements. All quadrature encoders resolve 2 x
the number of slots. Therefore 30 slots = 60 distinctly discernible axle
positions.

Several people have used mice in DIY CNC machinery. Some have used them as
is (like me), connected to a PC serial port.

Peter

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2001\08\02@193642 by Andy N1YEW

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On Thu, 02 Aug 2001, you wrote:
> > resolution
>
> ...near 100 dpi with the original ball & axle.............

mine is 400 DPI for 5 bucks :-D

andy

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2001\08\03@094106 by Douglas Butler

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100 dpi is still an order of magnitude below the 1/1000" he is looking
for.  10x mechanical magnification without backlash is doable, but not
trivial.

Sherpa Doug

> {Original Message removed}

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