Re: Connection of hardware

[johnm-at-slmd.com]

>> I forsee a bunch of coding I'll have to do to obtain the spindle speed.
>> If I ask for 1300 rpm, it doesn't really have to be that exactly as long
>> as I know what it is (e.g., 1304.67 rpm) to coordinate threading tasks.

> I also want to use emc for lathe tasks and need the threading and high
> speed spindle coordinated with z.  Don't have a clue how to do it.

I only see here the problem of reading the encoder output that tells us
the speed of the spindle -- altering the way one of the Y axis is used
(since I only need X and Z) to show the resulting velocity (rather than
position) and not have closed-loop PID servo control enabled for it.

>> I'm a long way from getting there yet. I'm not going to use xemc as is
>> anyway since I want to personalize it (and I'm a X-Windows/Motif gui
>> expert).

> Sounds like you need to be a member of the EMC gui committee that Fred
wrote
> of today.

Since I'm doing this anyway, I wouldn't mind it a bit. I'm rather strict in
using the Motif Style guide for consistent GUI appearance so the look and
feel
would probably look much different than xemc. Also, it would probably use
Lesstif rather than Motif per say to make it openly available.

>> There are opto-22 "quadrature" input modules that advertize to be used
for
>> encoders,
>> but I know nothing about what I'm talking about, so I'm probably wrong :
-(
>>
>> See http://www.opto22.com/datasheets/1053_SNAP_Quadrature.pdf
>>
>> They advertize that the max RPM allowed is 1,500,000 / encoder's pulses
per
>> revolution

> I skimmed the .pdf listed and I don't think the output of these is
compatable
> with anything that I've seen around emc.  They put out a square wave
pulse
> each time the quadrature signal changes state. The pulse will be on one
> output if the rotation is forward and another if it's reverse.  The rack
> that this module goes into must implement an up down counter.  The max
> rpm with one degree resolution (360 ppr) would be about 4100 rpm.

Jon set me straight on this point, I don't need any opto-isolation to the
encoders. Here, my ignorace of electronics showed its ugly face -- I was
confused
by the STG "opto22 compatible" pin descriptions and the STG 50-pin
connector not
having a wire screw interface (where as the opto22 racks did) making me
think
every wire needed to be connected via opto-isolation I/O modules.
(insert laughter here).

> I'm not convinced that you need opto isolation on the quadrature
> input to the stg board.  I'd use isolation on all the input signals.  And
> use sockets so that I could replace smoked isolators.

Sockets suggests home-made electronics -- don't I/O modules have fuses?
Jon says one only needs opto-isolation only on output signals. Transient
EMF
experts out there please clearify the rules!


> If the outputs went to an NPN transistor and pulled a relay near the stg,
> I don't think I'd bother there either -- just use the relay to isolate
> power and load.



> Jon E. had some breakout boards.  We really should work up a general
> purpose stg interface board plan and get some made up for all the
signals.

> Ray

I'm totally in favor of the latter since one can go nuts organizing and
re-organizing layouts of these boards.

John