PLS-601 User's Manual
Document #11696 Page - 3
1.0 SCOPE
The purpose of this User's Manual is to describe the operation, installation and programming of
the Toledo Transducer's PLS-601 Programmable Limit Switch. It is strongly recommended that
this User's Manual be read entirely before placing the PLS-601 into operation. Failure to follow
the instructions given in this User's Manual may void your PLS-601 warranty.
Questions regarding any aspect of the PLS-601 should be referred to Toledo Transducers, Inc.:
Toledo Transducers, Inc.
6834 S pring Valley Drive
Holland, Ohio 43528
Phone: (419) 867-4170
Fax:
(419) 867-4180
2.0 PROGRAMMABLE LIMIT SWITCH FUNCTIONAL DESCRIPTION
A wide variety of industrial applications require that an electrical switch be turned ON and OFF at
exactly the same point in each cycle of machine operation. The point in the machine cycle that the
switch is turned ON is commonly known as the TIMING, whereas the length of time that the
switch is ON is termed the DWELL.
TIMING and DWELL can be provided by mounting a mechanical cam on a rotating shaft, such
that it can make contact with a corresponding electrical switch. The portion of the cam that comes
into actual contact with the switch is often known as the LOBE. The design of the cam must allow
the user to be able to set both the TIMING and DWELL of the LOBE.
Several cam/switch assemblies can be placed on the same shaft, to provide independent TIMING
and DWELL for a number of different machine functions. Each cam/switch assembly is
commonly known as a CIRCUIT.
Mechanical cam switches can be very time consuming to set when more than a few circuits are
required. In addition, mechanical cam switches are not practical in applications where the switch
must be turned ON and OFF a number of times during a single machine cycle (MULTIPLE
LOBES).
A programmable limit switch is a device which overcomes the shortcomings of mechanical cam
switches by performing the cam functions electronically rather than mechanically. Instead of
having to physically adjust the TIMING and DWELL of a number of mechanical cams, the
programmable limit switch (PLS) allows a user to enter the TIMING and DWELL settings via a
keyboard. The TIMING and DWELL settings are then stored in a solid state memory and used to
control whether the outputs of the electronic switches are turned ON or OFF.
Because of the relative low cost of today's solid state memories, a PLS can readily accommodate
applications requiring a large number of circuits, each with single or multiple LOBES.
