Version 4.1. Updated 08/00 How to Use Integrated Pulse Outputs for Open-Loop Control Positioning with a Stepper Motor (Tip 23) Category: Positioning Special Hardware Requirements:  

l One SIMATIC S7-200 CPU (224, 226, 226XM) Because a pulse output is used in this tip, a CPU with DC power supply, DC inputs, and DC outputs (DC/DC/DC) is required.

l One PC/PPI cable l One programming device or PC l One SIMOSTEP stepper motor, rated load torque 2 Nm, rated current IN = 1.8 A

Order number: 1FL3041-0AC31-0BG0 You can find technical specifications in the online catalog CA 01, URL: http://www.ad.siemens.de/

l One FM STEPDRIVE Order number: 6SN1-227-2ED10-0HA0 You can find technical specifications in the online catalog CA 01, URL: http://www.ad.siemens.de/

l One motor cable, 10 m Order number: 6FX5-008 5AA00 1BA0

l One sub D connector, 15-pin, for FM STEPDRIVE Order number: 6FC9 348 7HX

l One voltage transformer 24 VDC/5 VDC Adaptation of the voltage levels of the outputs of the S7-200 to the pulse interface of the FM STEPDRIVE

l Resistors or Calex Model 8502 You can find data sheets under: http://www.calex.com or http://www.recom-electronic.com

l One cable for control signals to power section l One simulator for S7-200

Project Example

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Positioning tasks differentiate between closed-loop control and open -loop control operations. Stepper motors do not require continuous position control and therefore are used in open-loop control mode. This program example achieves relative positioning with a stepper motor drive by using the integrated pulse outputs of the SIMATIC S7-200 CPU 224.

Although a reference point is not necessary for this type of positioning, the example describes a simple procedure for specifying a reference bit because, from a practical standpoint, it makes sense to assign a fixed reference point to an axis.

Next, this example program uses an input byte in binary format to provide the CPU with the positioning angle. From this information, the program then calculates the number of required positioning steps and causes the CPU to read out a corresponding number of control pulses.

Description FM STEPDRIVE

The FM STEPDRIVE power section is used to drive three-phase stepper motors. Motors in the lower range of performance can be driven with 5 W to 600 W.

Interfaces of the FM STEPDRIVE Power Section

Pulse Interface

The module can be driven with clock signals of a higher level positioning unit by means of the pulse

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interface. For each clock pulse, the motor executes one step. Note: The pulse interface has 5V optocoupler inputs and therefore cannot be connected to the controller directly.

Note:  The pulse interface has 5V optocoupler inputs and therefore cannot be connected to the controller directly.

Signal Interface

The signals of the higher level controller that are fed in at the PULSES input can be enabled for driving the motor by means of the GATE_N input of the signal interface.

The signal interface has 24V inputs.

Parameters of the FM STEPDRIVE

You assign parameters for the motor phase current, the number of steps, and the current decrement by means of the switch for current and parameter.

Selector switch for motor phase current: 0   -> IN = 1.7 A (for SIMOSTEP stepper motor 1FL3041 0AC31 0BG0)

Input Signals:

PULSE Clock pulse Each positive pulse edge causes one step of the motor if it is ready to run and has 24 V at the GATE N input.

DIR Direction of rotation For a de-energized signal input DIR, the motor turns clockwise; for an energized signal input, the motor turns counterclockwise.

ENABLE Enable If the ENABLE input is energized, the power section is enabled.

PWM Current control The level of the motor phase current that is set can be changed with a pulse width modulated signal.

Output signals:

READY1_N Ready status After the ENABLE input is activated, the power section reports that it is ready by means of the output READY1_N.

Inputs:    

GATE_N Enables the clock pulse signal

When there are 24 V at the GATE_N input, the signals that are pending at the PULSES input are used for driving the stepper motor. For 0 V, the pending signals are disabled.

Outputs:    

ZERO Zero signal ring counter

In the zero position of the internal ring counter, there are 24 V at the ZERO output.

READY2 Ready status After the ENABLE input is activated, the power section reports that it is ready by means of the READY2 output.

MSTILL Motor stopped If the clock pulse signal is disabled by means of the GATE_N input and the motor is brought to a standstill, this standstill is acknowledged by the MSTILL sign.

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Voltage Conversion for the Driver of the Stepper Motor

The following figures show how you can easily create a circuit in order to connect the programmable logic controller to the drive of the stepper motor that requires a 5V current-sinking signal.

As an option, you can also use a Calex converter (such as a Model 8502) to generate a 5V current-sinking signal.

As an option, you can also use a Calex converter (such as a Model 8502) to generate a 5V current-sinking signal.

Note: For the pulse train output (PTO) function, the switching times of the outputs for the switching procedures On/Off and Off/On are different. This difference is evident as a distortion of the relative duty cycle. The PTO outputs require a minimum load of 10% of the rated load in order to generate clean transitions. Without the load, the stepper motor could lose steps when switching from one pulse rate to another.

Program Description

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Input and Output Definitions

Copyright 2002 Siemens Energy & Automation

SIMATIC S7-200 customers have free use of the application tips. These tips are only a general approach to using the S7-200 with various applications.

Your specific application may be different. It is your responsibility to use the SIMATIC S7-200 properly in your applications.

Inputs:

I0.0 to I0.7 Reference Angle (in binary format)

I1.0 Motor START

I1.1 Motor STOP

I1.4 Set/Delete Reference Angle

I1.5 Direction of Rotation

Outputs:

Q0.0 Pulse Output

Q0.2 Direction of Rotation Indicator

Q0.3 Drive Enabled Indicator

Q1.0 Reference Angle Indicator

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