"Pete C." wrote:
Ignoramus15939 wrote:
On 2010-07-12, Pete C. wrote:
Ignoramus15939 wrote:
On 2010-07-12, Pete C. wrote:
Ignoramus15939 wrote:
Sorry for a lousy picture.
http://igor.chudov.com/projects/Brid...d-Up-Computer/
Encoder cable is next for tonight.
i
Excellent! You'll have a lot more fun once you have the servo loop
closed and can play around with precise positioning, accel/decel,
homing, etc. Remember to wire the index signal from your encoders back
to the control for eventual use for precise homing.
I will definitely use the index signal. As of now, I do not even know,
yet, if my encoders work at all.
Another big chunk of work is wiring all external things like limit
switches, buttons etc.
i
If you get ambitious, think about adding decel switches to allow you to
home at rapid rate most of the way.
My mill does approximately 70 IPM right now, I think that it is slow
enough for homing, no?
i
Most likely not, but it depends on how fast your decel rate ends up set
at. You will probably want to home at around 10 IPM so you can drop down
to 1 IPM when you detect the limit switch and creep up on the index
without overshooting it. You'll figure it out once you start testing
your homing. You can also either adjust your limit switch position
slightly, or your encoder position on the motor shaft so that the index
pulse isn't too close behind the limit switch trip point.
The key thing with decel switches is that they allow you to home at
rapid speed most of the way through the homing process, which on a
machine with long travels and high rapid speeds can make a significant
difference in homing time.
Crappy ASCII art for homing sequence:
----------|----------|---------| (home)
(rapid) ^ (slow) ^ (creep) ^
D L I
e i n
c m d
e i e
l t x
You rapid travel in the home direction until you hit the decel switch
about an inch out from the limit switch. When you hit the decel switch
you drop from rapid to slow until you hit the limit switch. When you hit
the limit switch you drops to creep for ~ 1/2 rev until you reach the
index signal at which point you stop and zero/home the axis.
Obviously if the axis happens to be near the home end at the start, the
decel setup doesn't make much difference, but if the axis is a few feet
from home, being able to rapid most of that distance saves a lot of
time.