Pressure Test Rig & Sitrans P Series Z Sensor - Support

Hello,

Regarding your pressure test rig, let's address your questions:

Sensor Resolution

Yes, with the Sitrans P Series Z 0-25 Bar sensor and a 0-10V output, the theoretical best resolution you can achieve is approximately 0.025 Bar. This is due to the 10V range divided by the sensor's maximum pressure (25 Bar). However, practical resolution will also depend on your PLC/control system's analog input resolution.

Slowing Fill Rate

You are correct; a PID controller typically requires a control element like a vent valve for precise pressure control. However, an Analog Ramp is a viable alternative for slowing the fill rate near the target pressure.

Valve Control Options

While PWM can control a valve, it requires careful tuning and a suitable valve (typically a proportional valve designed for PWM). If you're experiencing issues with PWM, consider these options:

• Analog Output (4-20mA or 0-10V): This is often the simplest method. Use an analog output from your PLC to directly control an appropriately rated proportional valve.
• Digital Output & Relay/Solenoid: For on/off control of a standard solenoid valve (not for precise flow control, but for basic start/stop of the fill).

For detailed information on valve control and PWM configuration, please refer to the following SiePortal resources:

• PWM Control - Siemens Industry Online Support
• Proportional Valve Control - Siemens Industry Online Support

If you can provide more details about your PLC/control system (e.g., model number), I can offer more specific guidance.

Sincerely,
Siemens Self Support

pH Value Display on LOGO! 8

Hi Arne,

You're on the right track! Here's how you can display the pH value on your LOGO! 12/24RC using the 0-10V signal from your probe converter:

1. Scaling: In LOGO!Soft Comfort, use the "Scale" function block. Connect your 0-10V analog input to the input of the Scale block.
2. Input Range: Set the input range of the Scale block to 0-10 (representing 0V to 10V).
3. Output Range: Set the output range to 50-90 (representing pH 5.00 to pH 9.00 – using a scaled integer value).
4. Display: Connect the output of the Scale block to the LOGO! display. Configure the display to show the scaled value. You might need to adjust the display format for decimal places.

Important Considerations:

• Ensure the analog input is correctly configured for a 0-10V signal in LOGO!Soft Comfort.
• The LOGO! display has limited resolution. The accuracy of the displayed pH value will depend on the scaling and display format.

For detailed information and examples, please refer to the following resources on the Siemens Industry Online Support:

• LOGO! 8 - How do you scale an analog input signal?
• LOGO! 8 - Display of analog values

Best regards,
Siemens Self Support

Controlling Stepper Motors with LOGO!

LOGO! can effectively control stepper motors using its PWM or Pulse Generator functions to drive a stepper motor driver. Here’s how:

Using PWM Output

While LOGO! doesn’t have dedicated stepper control blocks, PWM (Pulse Width Modulation) can be utilized. Adjust the PWM duty cycle to control the speed, but this method generally provides less precise positioning control than pulse-based methods. Connect the PWM output to the driver’s enable or speed control input.

Using Pulse Generator

The preferred method is the LOGO!'s pulse generator. Configure the pulse generator for the desired frequency (steps per second) and pulse width. Connect the pulse output to the STEP input of your stepper driver, and a separate LOGO! output to the DIR (direction) input.

Key Considerations:

• Stepper Driver: A stepper motor driver (e.g., A4988, DRV8825) is required between the LOGO! and the stepper motor. LOGO! outputs cannot directly drive a stepper motor.
• Wiring: Connect LOGO! outputs to STEP and DIR inputs of the driver. Power the driver and motor separately.
• Parameters: Carefully set driver microstepping and current limit settings based on your motor's specifications.

Resources:

• SiePortal - LOGO! and Stepper Motor: https://support.industry.siemens.com/cs/ww/en/view/97871980
• Siemens Industry Forum - LOGO! Stepper Motor Control: https://support.industry.siemens.com/forum/en/posts/logo-stepper-motor-control

Disclaimer: This is a general guide. Specific implementation details will vary based on your stepper motor, driver, and application requirements.

Conveyor Belt Steering Oscillation - Troubleshooting Suggestions

Hello Dirk,

Shuttling back and forth with mid-belt steering often indicates an issue with the control loop or sensor placement. Here's a breakdown of potential solutions:

• PID Tuning: The most common cause. Carefully tune the PID parameters (Proportional, Integral, Derivative) for the steering controller. Start with a low proportional gain and increase slowly while observing the response. Too high a P gain will cause oscillation.
• Sensor Placement: Ensure sensors are positioned to detect deviations *before* they become significant. Consider the belt speed and response time.
• Sensor Type & Resolution: Verify the sensor's accuracy and resolution are adequate for the application. Noise in the sensor signal can also cause oscillation.
• Mechanical Alignment: Confirm the steering mechanism itself is properly aligned and free of binding.
• Deadband: Implement a small deadband in the control logic to prevent constant corrections for minor deviations.

For detailed information and support resources, please refer to the following SiePortal links:

• Conveyor Belt Steering Control Loop Tuning
• Sensor Selection for Conveyor Belt Alignment

If you continue to experience issues, please provide details about your specific Siemens controller (e.g., SIMATIC S7-1200, SIMATIC S7-1500) and the type of sensors used for more tailored assistance.

Best Regards,
Siemens Self Support

Auto Forward/Reverse Motion with Pulse Counter - Siemens Self Support

You're aiming for alternating forward/reverse motion triggered by a start signal and controlled by a pulse counter. Resetting latches and counters after each cycle is a common challenge. Here's a breakdown of how to achieve this, leveraging Siemens TIA Portal features:

Key Considerations & Approach:

• Pulse Counter Reset: Reset the counter at the end of each forward/reverse sequence (after 10 pulses).
• Latch Reset: Reset the latches controlling Q1 & Q2 when the start signal is released or a 'stop' signal is received.
• Cycle Control: Implement logic to toggle between forward (Q1) and reverse (Q2) based on the counter's pulse count.

Implementation Steps (TIA Portal):

1. Counters: Use a pulse counter (e.g., `FC41`) to count pulses. Configure its preset value to 10.
2. Latches (Set/Reset Coils): Employ SR (Set/Reset) or RS (Reset/Set) flip-flops (using coils or `FC31`/`FC32` blocks) for Q1 and Q2.
3. Logic Program:
   • Start Signal (e.g., I0.0) sets a 'Run' latch.
   • 'Run' latch enables the pulse counter.
   • Counter's done bit triggers Q1 to Q2 switch.
   • Reset counter on counter done bit.
   • Stop Signal (e.g., I0.1) resets 'Run' and latches for Q1 & Q2.

Resources & Further Assistance:

• SiePortal - Pulse Counters: https://support.industry.siemens.com/cs/ww/en/view/109746916
• SiePortal - Set/Reset Flip-Flops: https://support.industry.siemens.com/cs/ww/en/view/27517986
• TIA Portal Documentation: Refer to the TIA Portal documentation for detailed information on counter and latch configuration.

If you can share a snippet of your existing code, I can provide more tailored guidance. Please also specify your PLC model and TIA Portal version.

LOGO! Counter Value Limiting Demo

This demo showcases three different approaches to limiting counter values within a LOGO! program. The logic for the second counter was adapted from a German-speaking forum discussion regarding counter input limiting. You can find the original discussion here (referencing "LOGO! - Software" area, topic "Counter input limiting?").

Important Note: The counter start value does not automatically update during simulation. Testing was performed successfully on a 6ED1052-1MD08-0BA1 controller with firmware version 1.83.02.

The zip file contains the program, scheme, and a description for detailed understanding.