Overview - Siemens SIMATIC S7-200 System Manual

S7-200 Programmable Controller System Manual

Overview

The S7-200 provides three methods of open loop motion control:
Pulse Width Modulation (PWM) -- built into the S7-200 for speed, position or duty cycle
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control
Pulse Train Output (PTO) -- built into the S7-200 for speed and position control
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EM 253 Position Module -- an add on module for speed and position control
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The S7-200 provides two digital outputs (Q0.0 and Q0.1) that can be configured using the Position
Control Wizard for use as either PWM or a PTO outputs. The Position Control Wizard can also be
used to configure the EM 253 Position Module.
Position
Control
When an output is configured for PWM operation, the cycle time of the output is fixed and the
pulse width or duty cycle of the pulse is controlled by your program. The variations in pulse width
can be used to control the speed or position in your application.
When an output is configured for PTO operation, a 50% duty cycle pulse train is generated for
open loop control of the speed and position for either stepper motors or servo motors. The built in
PTO function only provides the pulse train output. Direction and limit controls must be supplied by
your application program using I/O built into the PLC or provided by expansion modules.
The EM 253 Position Module provides a single pulse train output with integrated direction control,
disable and clear outputs. It also includes dedicated inputs which allow the module to be
configured for several modes of operation including automatic reference point seek. The module
provides a unified solution for open loop control of the speed and position for either stepper
motors or servo motors.
To simplify the use of position control in your application, STEP 7--Micro/WIN provides a Position
Control wizard that allows you to completely configure the PWM, PTO or Position module in
minutes. The wizard generates position instructions that you can use to provide dynamic control of
speed and position in your application. For the Position module STEP 7--Micro/WIN also provides
a control panel that allows you to control, monitor and test your motion operations.
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