Delta Tau GEO BRICK LV User Manual

If there is a following error when the HOMEZ command is given, the reported 
actual position after the HOMEZ command will not be exactly zero; it will be equal 
to the negative of the following error. 

Homing Into a Limit Switch 
It is possible to use a limit switch as a home switch.  However, first disable the limit function of the limit 
switch for the move to finish normally; if this is not done, the limit function will abort the homing search 
move.  Even so, the home position has been set; a J=0 command can then be used to move the motor to 
the home position. 

On PMAC-style servo channels, the polarity of the limit switches is the opposite of 
what many people would expect.  The -LIMn input should be connected to the 
limit switch at the positive end of travel; the +LIMn input should be connected to 
the limit switch at the negative end of travel. 

To disable the limit function of the switch, set bit 17 of variable Ixx24 (bit value $20000) for the motor to 
1.  It is a good idea to use the home offset parameter Ixx26 to bring the home position out of the limit 
switch, so the limits can be re-enabled immediately after the homing search move, without being in the 
limit. 

The following examples show two quick routines to do this type of homing.  One uses a motion program 
and the other a PLC program.  The same function could also be done with on-line commands. 

;*********** Motion Program Set-up Variables (to be saved) ************* 

 

 

; Home speed 10 cts/msec negative 

 

; PMAC-style flags, normal mode 

I125=$78000   

 

; Use Servo IC 0 Channel 1 flags for Motor 1  

I126=32000   

 

; Home offset of +2000 counts 

 

 

; (enough to take you out of the limit) 

I7102=3    

; Capture on rising flag and rising index 

 

 

; Use +LIM1 as flag (negative end switch) 

;*********** Motion program to execute routine ********************* 

OPEN PROG 101 CLEAR 
I124=$20000  

; Disable +/-LIM as limits 

   ; Home #1 into limit and offset out of it 

I124=$0     ; Re-enable +/-LIM as limits 
CLOSE 

   ; 

End 

of 

program 

;*********** PLC Set-up Variables (to be saved) ************************ 

CLOSE 
I123=-10  

 

; Home speed 10 cts/msec negative 

 

; PMAC-style flags, normal mode 

I125=$78000   

 

; Use Servo IC 0 Channel 1 flags for Motor 1  

 

; Home offset of +2000 counts 

 

; (enough to take you out of the limit) 

I902=3   

; Capture on rising flag and rising index 

I903=2   

; Use +LIM1 as flag (negative end switch) 

M133->X:$B0,13,1   

; Desired Velocity Zero bit 

M145->Y:$C0,10,1   

; Home complete bit