Systems Engineering Associates, Inc.

Systems Electronics Group, Inc.
14989 W. 69th Avenue Arvada, CO 80007
Tel: (303) 421-0484
Fax: (303) 421-8108
Programmable Limit Switch (PLS) Section

The PLS section is a high speed programmable limit or cam switch which accepts angular position information in the form of resolver format signals and converts these to digital. The M4500 is configured for 8, 16, 32, or 64 timing channels. These are mapped to internal memory locations of the M4500 for use by the PLC section or can be written to output boards for use in general PLS applications.

The timing channels can be programmed "on" and "off" at user defined position set-points. Each timing channel can be programmed with up to 50 unique "on-off" set-points or with a pulse train of fixed "on" and "off" divisions throughout the entire channel.

The scale factor of the PLS is programmable from 2 to 4096 divisions per revolution while the offset is programmable from 0 to one minus the scale factor. The PLS supports up to 8 PLS programs when 8 timing channels are used and the scale factor is less than 512 (less PLS programs when more channels are used or the scale factor is greater than 512).

A typical application utilizing multiple PLS programs is a stamping press where different die sets are used to produce different stampings. The timing signals for each die set (up to 8 different die sets) is programmed and saved in a specific PLS program. As different die sets are used, the corresponding PLS program is called up. This relieves the operator from reprogramming the timing signals each time a die set is changed.

Speed Compensation is available for timing channels 0 through 7. This is used to compensate for the mechanical response time of a device activated by a particular timing channel. The speed compensation algorithm "leads" the desired activation position by a time in milliseconds entered for that channel. Thus, as the speed increases, the point at which the device is activated is advanced to compensate for the response time of the device. Note that the setup is simplified by entering the compensation parameter in units of time (milliseconds) which directly reflects mechanical response, not in degrees per RPM as done by other PLS manufacturers.

Since the PLS is fully integrated with the PLC processor, advanced PLS features which allow much more sophisticated machine related timing algorithms can be performed as well.

For more information, download the complete M4500 User's Manual.

M4500 Product Line:

General System Features
System Configurations

PLC Section
Interrupt Inputs
Built-in Analog I/O
Diagnostics/Fault Detection

PLS Section
PLS Channel Programming
Advanced PLS Features

Digital I/O Boards
Analog I/O Boards
Communications Boards
Motion Control Boards
Power Supply
SYSdev Program
Development Software

Data Sheets by part number and User's Manuals

For pricing and availability, contact us


RSV34-MS1 Resolver

The RSV34-MS1 combines a brushless resolver, automotive rated double bearing shaft, flexible coupling, circular military spec connector, and a NEMA 4X housing to provide a very rugged and reliable position transducer. This is mounted on the machine and interfaces directly to the PLS section of the M4500 via a 6-conductor cable. From this, angular machine position can be determined and timing signals in the PLS section generated to control position dependent functions.


The resolver, double bearing shaft, and flexible coupling are mounted in a single, machined 6061 aluminum mount for maximum rigidity and strength. The housing is made of machined 1/4" thick 6061 aluminum for additional strength and protection for the resolver and sealed to provide NEMA 4X rated protection against solvent and fluid ingress.

The 7-pin circular military sped connector allows quick disconnection of the RSV34-MS1 while at the same time providing a high degree of reliability. The connector mates with a pre-fabricated cable assembly complete with either a straight or right-angle mating connector, cut to a user specified length.

click to enlarge
For more information, download the complete RSV34-MS1 data sheet.

PLS Channel Programming

The PLS section of the M4500 is programmed through SYSdev using a laptop or thru the D4591 Display/Keypad. When using SYSdev, the PLS section can either be configured and the timing channels programmed off-line and down-loaded to the M4500 or the PLS timing channels can be programmed on-line, while the M4500 is in operation. The laptop is interfaced to the PLS section via the "PROG" port of the M4500 using an RS-232 cable from the COM port on the computer. The following PLS programming commands are available:

  • PLS Configuration including: Scale Factor (2-4096), Offset, selected PLS Program (0-7), number of Timing Channels (8, 16, 32, or 64), timing channel Speed Compensation (channels 00 thru 07).
  • On and Off-line timing channel programming including: Single Set-point programming, Pulse Train programming, timing channel Fine Tune (SYSdev only).
  • Channel set-points download to M4500 (SYSdev only)
  • Channel set-points upload from M4500 (SYSdev only)
  • Configuration and channel set-points print-outs (SYSdev only)

Advanced PLS Features

The PLS is fully integrated with the PLC. Thus, the actual resolver position, current RPM, and all other PLS parameters can be accessed by the PLC section. The PLC can also execute the PLS programming commands that would normally be executed through SYSdev or the D4591 Display/Keypad. This allows a wide variety of advanced PLS applications to be implemented. Examples are:

Brake Wear Compensation: The brake wear compensation algorithm is used in conjunction with presses which incorporate a top dead center (TDC) or back dead center (BDC) stop. With these presses, a timing signal is used to de-clutch the press for TDC or BDC stops. However, as the brake wears, the press will no longer stop at TDC but will instead overshoot. The brake wear compensation algorithm automatically adjust the TDC timing such that the press always stops at the desired stopping position regardless of brake wear.

Brake Wear Alarm: In conjunction with the brake wear compensation, brake response determination and a brake wear alarm can be implemented in the PLC section. This determines the actual number of degrees the brake takes to stop the press (from de-clutch to stop). The brake wear alarm can be activated if the brake response exceeds a preset number of degrees.

Speed Windows: These signals can be activated at preset speed thresholds as desired or needed. Since the RPM is directly available to the PLC section, virtually an unlimited number of speed windows could be generated by the PLC section.

Automatic Zero: Since the offset of the PLS can be accessed by the PLC section, it can also be changed in response to any desired logic condition, even as a function of speed which would, in affect, implement a speed compensation for all the timing channels.