Axis Homing not working correctly?

BigJohnT wrote:

I assume you had the same result?

Did you test the index for proper polarity?

gnipsel.com/linuxcnc/tuning/encoder.html

John

It says use setp but I don't get what i need to type. looking at the configuration watch list index enable just blinks once and stays off. From the link you provided it appears that this is backwards and I need to reverse the polarity. Should I redo the connections on the encoder itself or is there a software change that can be made?

From the HAL file:
##################################################################
#
# W axis
#
net W-motor-pos-fb ppmc.0.encoder.02.position axis.8.motor-pos-fb pid.8.feedback # motor feedback
net Woutput pid.8.output ppmc.0.DAC.02.value # motor pid to DAC
net Wpos-cmd axis.8.motor-pos-cmd pid.8.command # position command into PIDs
net Wenable axis.8.amp-enable-out pid.8.enable # enable PIDs
net Windex axis.8.index-enable ppmc.0.encoder.02.index-enable # homing connection
#
setp ppmc.0.encoder.02.scale [AXIS_8]MOTOR_ENC_SCALE
#
setp pid.8.maxoutput [AXIS_8]MAX_VELOCITY
#
setp axis.8.jog-vel-mode true
#
setp ppmc.0.DAC.02.scale [AXIS_8]OUTPUT_SCALE
#
# set PID loop gains
setp pid.8.Pgain [AXIS_8]P
setp pid.8.Igain [AXIS_8]I
setp pid.8.Dgain [AXIS_8]D
setp pid.8.bias [AXIS_8]BIAS
setp pid.8.FF0 [AXIS_8]FF0
setp pid.8.FF1 [AXIS_8]FF1
setp pid.8.FF2 [AXIS_8]FF2
setp pid.8.deadband [AXIS_8]DEADBAND
#
########################################################################################################################################

Is the switch logic the same for the W home switch as the other axis? ( more important is it what linuxcnc expects)
And does the axis movement direction agree with the machine thinks it's doing?
You can look at the AXIS plot to see if the directions match. (remembering AXIS shows TOOL movement not machine movement)

Both of these can make the machine seem to start homing properly but will not finish properly.

Chris M

John I have not been able to follow your request. I will look at that in the morning and watch the axis preview a Chris has sugesated. I did notice and for got to mention that it starts homing in the direction I tell it to. It makes the switch and then backs off the switch. That is where the problem seems to be. On the DRO it increments + to make the switch and then reverses -. I know from testing it takes right at 1' of movement to get off the switch. When it gets to that 1" mark it starts counting down to the position where it was when EMC loaded up.

TOUCHY doesn't give access to halshow.

If you open a terminal (while TOUCHY is running) and type: halcmd loadusr halmeter then right click the top of halmeter and set always-on-top
then you can watch the halpins change ( you can do it multiple times for multiple halmeters.)
Maybe you already know this.

when it starts to go back to where it started, does it ever stop? If not then it most likely means it's still searching for the switch/ or index.

Chris M

I would also consider giving search velocity and final velocity slightly different speeds so you can tell what linuxcnc is doing just be the sound/speed.

Chris M

It turned out to be a bad port on the PPMC card. All seems to be going well now thanks.