Re: [CAD_CAM_EDM_DRO] PIC DRO Revisited

> I have been programming PICs for a few years, and am cosidering
> making a 3 axis DRO. I would be more than glad to share my
> design,code,schematics with all. Having never worked with a DRO, I
> have a couple of questions.

Suggest you do some reading on encoders - you might look at www.usdigital.com

> How does the DRO know which direction the
> motor is going (so it can increment or decrement). Also what
> properties do the average encoders have (e.g. opto
> using a 5 volt supply, hall effect) do they pulse a signal out or
> need a supply voltage etc.

Typical encoders you might encounter might need 5v power and give 5v
signals either TTL compatible (cheap ones) or differential (expensive
ones). The signals are usually two square waves 90 degree out of
phase, sometimes with an additional index channel. You tell the
direction of the count from the sequence of rising and falling edges
of these two quadrature signals. Alternately, you can get a chip like
the LS7084 that converts qaudrature to step and direction signals.

> I was thinking of using a seperate color of LED diplay for each
> axis.

I'd probably opt for all Red LED's or some other display technology,
as the other color LED's are not as bright, and you might have trouble
equalizing the brightness of the 3 axis.

>Besides a button to zero each axis are there any other features
> I need to consider?

Someone mentioned a nify mode switch to put the readout in an
incremental mode. Basically, you store the current position, then let
the user reset the counter to make little local measurements, then
restore the original count once they set the mode switch back to
absolute. Hitting the reset button in absolute does a reset of this
absolute position counter.

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
30 Griswold Street, Cambridge, MA 02138
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