Service manual

15
EXPLANATION OF COMPUTER SYSTEM
SYSTEM ACTIVATION
All posts on this system are identical (there is no master or slave columns). After the posts are connected as
described in the lift setup, the lift is ready to be activated. As each post is turned on, they “search” for each
other, establishing a shared network for synchronizing and controlling the lift as a system.
The first thing the user must do to operate the lift is to verify that the network is detecting the desired number
of columns to use. Pressing the selection key arrow to the right of “YES” will allow the user to begin raising
and lowering the lift.
Example Screen shows lift with 4 posts present in system, Post
#1, #2, #3, and #4. Pressing the right selection key arrow will
activate lift.
Post presence will be affected by how many posts are
connected in the system, if they are connected properly (see
lift setup), if the dummy plugs are connected properly (see lift
setup), and if they are turned on (to “Operate Lift”).
OPERATION OF SYNCHRONIZED LIFTING OR LOWERING
Each PLC (programmable logic controller) is “addressed” which establishes its identity on the network. For
example, post #1 has a PLC with address #1, etc. Once communication of the network of PLCs is established,
each PLC senses control and position inputs from each other. Be aware that pairs are designated as post #1&2,
post #3&4, post #5&6, and post #7&8, regardless of where they are physically placed in the system.
The height of each carriage above floor level is measured by string potentiometers (see next section) and
compared to the other carriages by the PLC network. During raising, if any one carriage position is more than
1” higher than the lowest carriage, the higher (fastest) one slows down or stops to allow the lowest (slowest)
one to catch up. During lowering, if any one carriage position is more than 1” lower than the highest carriage,
the lower one slows down or stops to allow the highest one to catch up. This is all done by shifting motor
contactors and lowering solenoid valve.
When lifting in Pair or Single mode, counting is not done, resulting in the PLC’s seeing a “synchronized”
state after this adjustment is made. There are limits on how far the lift will allow a Single post to raise/lower,
and how far a Pair of posts can raise/lower relative to the rest of the system.
If you turn off the unit or press the Emergency Stop button, the computer position for each column is still
retained and the columns will still maintain synchronized relative positions.