Re: Re: emc help

Hi Greg

Don't take this as an attack. Let's just compare "facts." You may well
be correct in your assessment of my understanding of encoders but my
post addressed the reading of encoder output by the STG card itself rather
than the output of any specific encoder that you might connect to such a
board. Let me separate out these issues and attack them one at a time.

First, checking my facts, and quoting from page 3, text line 12 of the STG
"ISA Bus Servo I/O Card Hardware Manual" dated 1997.

"* Up to 10 MHz input rate"

I suppose that I should have qualified my 10 MHz comment with an "up to."
I'm wondering where you get your assertion that it's abilities are much
lower? Have you applied these boards to retrofits?

Second, if what you say about encoder output speed is accurate, how do
folk like Mazak apply those encoders that put out anywhere from 125K to
1M PPR with direct connection to ball screws spinning at 500 or more RPM?

Third, Jon Elson's use of the parallel port is not for individual step
pulses. He is sharing 8 bit wide digital signals that carry his
velocity commands and encoder feedbacks with his remote device using the
EPP or ECP protocol.

Last, if the credentials of "whoever" is important to you contact me off
list.

Ray

> From: "Greg" <gkretro@...>
> Subject: Re: emc help
>
> -
> Hello,
> Whoever wrote this doesnt know much about encoders.
> I use hiedhain encoders and they are expensive but they have a max
> encoder freq of 300khz which is double the normal spec of most other
> encoders.
>
> The only exception to this i have found is laser encoders made by
> canon.(Way to expensive)
> Also if you check your specs on the STG board the max enoder freq is
> not 10 mhz but much lower.
>
> And of course the parallel port could not run at these speed.
> And even the pico systems is limited to 300khz
>
> Regards,
> Greg
>
> -- In CAD_CAM_EDM_DRO@yahoogroups.com, Ray Henry <rehenry@u...> wrote:
> > > From: Jon Elson <elson@p...>
> >
> > <s>
> >
> > > Most encoder counters can handle 300,000 to 1 million encoder
> > > counts/second. So, that would be 30 to 100 inches a second, or
>
> 1800 to
>
> > > 6000 IPM. Is that enough for you?
> >
> > STG claims 10 MHz.. In theory you can multiply these values by 10
>
> so you
>
> > could be dealing in miles per minute.
> >
> > Ray