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Use Of Sequencer Functions In Industrial Control

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2004 Annual Conference


Salt Lake City, Utah

Publication Date

June 20, 2004

Start Date

June 20, 2004

End Date

June 23, 2004



Conference Session

Curriculum Development in Electromechanical Engineering Technology

Page Count


Page Numbers

9.1357.1 - 9.1357.10



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Paper Authors

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Max Rabiee

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 1449

Use of Sequencer Functions in Industrial Control

Max Rabiee, Ph.D., P.E. University of Cincinnati


In this paper we will study one of the most commonly used functions in programmable logic controller (PLC) systems. This function is called the Sequencer. All programmable logic controllers (PLC) have this function. The sequencer function provides powerful capability for the PLC. This function and its applications are studied as part of a logic controller course in Electrical and Computer Engineering Technology (ECET) programs.

Some PLC manufacturers refer to the sequencer function as the “drum controller”. However, in certain cases PLC manufacturers use the Table-to-Register or File-to-Word functions instead of the sequencer function [1]. These functions are not as versatile as the sequencer function.

In this paper we will illustrate how students can utilize the sequencer function in the laboratory for controlling electromechanical actuators and robots. We will also illustrate how to control the time period between each sequencer step.


Sequencer functions can be used to control multiple outputs with several step patterns. This means that in every sequenced step, you can change the state of the output devices connected to the output ports housed in output modules. Output can change from the ON to OFF state, or from the OFF to ON state, or remain at the same state.

In this paper, we will study the use of sequencer functions in programmable logic controller systems. We will discuss how Sequencer functions are used to control output with multiple step patterns. Specifically, we will study the use of sequencer functions for the Allen-Bradley SLC500 series programmable logic controllers [2]. These sequencer functions are: (1) SQO (Sequencer Output) function, (2) SQI (Sequencer Input) or SQL (Sequencer Load) function, and (3) SQC (Sequencer Compare) function. An Allen-Bradley SLC 500 Series Programmable Logic

Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright 2004, American Society for Engineering Education

Rabiee, M. (2004, June), Use Of Sequencer Functions In Industrial Control Paper presented at 2004 Annual Conference, Salt Lake City, Utah. 10.18260/1-2--12948

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