Saia PCD2.H310, Manual

Page: 97 / 154

PCD2.H31x Application examples
26/762 E2
(2H3-12-E.DOC)
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SAIA-Burgess Electronics Ltd. Page 12-3
An assumption is made that, in normal cases, the carriage is located be-
tween the positions 'Ref' and 'LS2'. For homing, the carriage should travel
in the direction of the reference switch, i.e. searching in a 'backwards' di-
rection. On reaching the reference switch it should travel freely in a for-
wards direction until it arrives at the next index signal of the incremental
shaft encoder. This means that the reference position has been reached
and the travel program can start.
For this purpose, the following parameters should be set for FB 'Home':
LD R 1010 ; PCD register with velocity for free
500 ; travel of the reference switch (slow)
LD R 1011 ; PCD register with velocity for seeking
5000 ; the reference switch (fast)
CFB Home ; Call FB 'Home'
K 1 ; Par 1: Module number
0 ; Par 2: Search backwards
1 ; Par 3: Free travel forwards
R 1010 ; Par 4: Velocity for free travel
R 1011 ; Par 5: Velocity for search
30 ; Par 6. Timeout 30s
I 64 ; Par 7: Reference input address
Behaviour under various starting positions:
a) Starting position 'normal' (carriage between 'Ref' position and
'LS2'): Behaviour as described above. If the reference point is
not found within a defined timeout, homing is halted. If the ref-
erence switch is activated on power-up (carriage located on ref-
erence switch), free travel only takes place and travel to the next
index signal.
b) Starting position with carriage between 'LS1' and 'Ref': The car-
riage first travels backwards to 'LS1', then forwards to reference
switch 'Ref'. The reference switch is travelled over at the veloc-
ity of free travel. After this free travel, it again travels on until it
reaches the next index signal of the incremental shaft encoder.
This means that the home position has been reached and the
travel program can start.
c) Starting position located to the right of 'LS2': Homing proceeds
as with a). 'LS2' is travelled over and does not affect homing.
d) Starting position located to the left of 'LS1'. The carriage travels
backwards as defined until the final limit switch. The home po-
sition cannot be found. If the final limit switch is not reached
within the defined timeout, homing is halted.