Re: [CAD_CAM_EDM_DRO] encoder indexing pulse

Carey,

Don't know why there would be "dual A" & "dual B" channels (an inverted
pair?), As to the index channel, it will go "active" once a rev,
probably not much use unless you "count" them, and then *AND* with an
index. Looks like they're more useful when you have single rotation to
watch (I could have used them on my RDF antenna rotator stepper
project).

You will want to use a logic gate, I.E., a 7400, 74HC00 or similar
*AND* gate. Sorry, you can't just hook them up in series! You probably
want separate inputs from each limit and the indexes; software might
watch for a "close" limit, and gate (AND) with the index to "home in",
as you suggest.

Steppers and limit switches are often used in combination, a "phase" of
the stepper drive is "ANDED" together to give a very "tight" signal
(otherwise the simple optical sensors e.g. floppy drives, would be too
"wide").

The optical outputs are pretty safe, just like optical isolators, but if
you add logic to their output, you might want to keep that logic (and
power) on the PC side.

Hope this helps

Alan



"Carey L. Culpepper" wrote:

>
> Since encoders seem to be a hot topic lately, I have a question of my
> own. The NEMA42 Compumotor steppers that I have mounted on my Bridgeport
> conversion are equipped with BEI encoders. I called yesterday to BEI and
> they were nice enough to send me the spec sheets pertaining to my
> encoders since I was clueless as to how to hook them up to my new
> Camtronics DRO board. The plan is closed loop operation. OK finally to
> the question. These encoders have dual channel (2A&2B channels) plus an
> index channel. I want to use the index channel for limit and homing
> switching in conjuntion with another set of optical switches. The theory
> being the first optical switch is tripped when things are close and the
> index channel would stop it right on the exact step every time. Using a
> logic "AND" circuit. This is not my brilliant idea. The Vexta manual for
> one of my 5 phase drivers suggested this method but not with an encoder
> but a "timing" output( a counter gives a pulse for every 10 steps. The
> manual recommends shutting the system down when homed this way. When the
> system is powered up it won,t jump steps.
> What kind of circuitry do I need to carry this out? The optical switch
> would be one of those led units probably much the same as the encoder
> itself. Probably a 5V input to power up the led. Could it be as simple
> as putting 5V to the optical and hooking the output in series with the
> index channel output and then to the parallel port? Would I need an
> opto-coupler for protection of the PC? Any use for the second set of
> encoder channels?
>
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