Re: emc help

HEllo,
I personally dont use the stg board i like galil boards much
better,better specs,bullet proof design,and overnight repair
capability if needed.
I have talked to the engineers of stg and they only recomended the
board to around 2 MHZ ( i should qualify this as that is in an
industrial enviroment).
This is what forced my trend towards galil

I have a lot of these boards in the field and have only had one go
bad (power supply overvolted)even when they are in some really bad
enviroments.

But apples and oranges it doesnt matter your encoder max freq is
going to be the limited either way ,unless you are using a laser.
Which is too costly for all but the most expensive machines.

As to the mazak spec ,I havent worked on a lot of them and it would
depend on if it had a fanuc or mazatrol control.
But if i rember right they have both abosulute encoders and count
interpolation giving the much higher density (full qudratic)
Thus the big differences in the statements pulses per rev and counts
per rev.

I would doubt that they reach a millioncounts a rev would be over
kill.
40000 ct/rev with a +/-2 lock factor would give you a .0001
resoulution,not counting the fact that you have a multiplication you
get from the ball screw ,which would reduce your needed encoder
resoulution even more
10000 ct/rev * 4 turns per inch =40000 ct rev
4 turns per inch *6.66 inch per sec or 400 ipm = 1440 rpm
all said and done leave you with an enocder freq of 240k
Being a japanese machine the ballscrews would be metric and the
smallest increment would most likely be .001 mm thusly changing these
number some.

My comment about the parallel was not against jon and his pico system
but in reference to step and dirrection signals,where you are max freq
limited.
With pico system the parallel port is just a communictaion port
passing the desired speed,position,etc to controller/drive.

-- In CAD_CAM_EDM_DRO@yahoogroups.com, Ray Henry <rehenry@u...> wrote:

>
> 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@e...>
> > 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