Unitronics Function Blocks for Pump Control: Complete Programming Guide

Optimizing Function Blocks performance for Pump Control applications in Unitronics's VisiLogic / UniLogic requires understanding both the platform's capabilities and the specific demands of Water & Wastewater. This guide focuses on proven optimization techniques that deliver measurable improvements in cycle time, reliability, and system responsiveness.

Unitronics's VisiLogic / UniLogic offers powerful tools for Function Blocks programming, particularly when targeting intermediate applications like Pump Control. With 1% market share and extensive deployment in US small, Unitronics has refined its platform based on real-world performance requirements from thousands of installations.

Performance considerations for Pump Control systems extend beyond basic functionality. Critical factors include 5 sensor types requiring fast scan times, 5 actuators demanding precise timing, and the need to handle pressure regulation. The Function Blocks approach addresses these requirements through visual representation of signal flow, enabling scan times that meet even demanding Water & Wastewater applications.

This guide dives deep into optimization strategies including memory management, execution order optimization, Function Blocks-specific performance tuning, and Unitronics-specific features that accelerate Pump Control applications. You'll learn techniques used by experienced Unitronics programmers to achieve maximum performance while maintaining code clarity and maintainability.

Unitronics VisiLogic / UniLogic for Pump Control

Unitronics takes a distinctive approach to PLC programming: every controller ships with an integrated colour touchscreen HMI, and the development tool handles PLC logic and HMI design in a single workspace. VisiLogic is the legacy tool for the Vision, Samba, and Jazz product families; UniLogic is the current-generation environment for the UniStream line. Both are free to download and include a complete built-in simulator covering PLC logic, HMI screens, alarms, recipes, and data tables — the sim...

Platform Strengths for Pump Control:

Combined PLC + HMI in one unit reduces panel cost

Free VisiLogic and UniLogic IDEs

Built-in simulator with both PLC and HMI simulation

Strong US small-integrator community

Unique ${brand.software} Features:

Combined PLC + HMI in one unit across Jazz, Samba, Vision, and UniStream

Free VisiLogic (legacy) and UniLogic (current) IDEs

Built-in simulator covering PLC logic, HMI, alarms, data tables, and recipes

Integrated data sampling and trend logging without separate SCADA

Key Capabilities:

The VisiLogic / UniLogic environment excels at Pump Control applications through its combined plc + hmi in one unit reduces panel cost. This is particularly valuable when working with the 5 sensor types typically found in Pump Control systems, including Pressure transmitters, Flow meters, Level sensors.

Control Equipment for Pump Control:

Centrifugal pumps for high flow applications

Positive displacement pumps for metering

Submersible pumps for wet well applications

Booster pump systems for pressure maintenance

Unitronics's controller families for Pump Control include:

Jazz 2: Suitable for intermediate Pump Control applications

Samba 7": Suitable for intermediate Pump Control applications

Vision V350: Suitable for intermediate Pump Control applications

Vision V570: Suitable for intermediate Pump Control applications

Hardware Selection Guidance:

CPU selection across Unitronics ranges from the Jazz 2 micro series (tiny applications, basic motor control, simple process monitoring with 10-20 I/O) through Samba 7" (small machine control with touchscreen HMI), Vision V350/V570 (medium machinery with larger HMI), and UniStream 7" / 15.6" (flagship combined PLC+HMI for mid-to-high complexity applications with advanced features like UniCloud, cel...

Industry Recognition:

Moderate - US small-integrator market, OEM machines, building automation. Unitronics' combined PLC+HMI controllers are uncommon in high-volume automotive manufacturing but appear in automotive tier-2 and tier-3 supplier shops, single-machine workcells, and after-market test fixtures. The cost advantage and single-unit PLC+HMI approach makes Unitronics attractive for small...

Investment Considerations:

With $$ pricing, Unitronics positions itself in the mid-range segment. For Pump Control projects requiring intermediate skill levels and 2-4 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.

Understanding Function Blocks for Pump Control

Function Block Diagram (FBD) is a graphical programming language where functions and function blocks are represented as boxes connected by signal lines. Data flows from left to right through the network.

Execution Model:

Blocks execute based on data dependencies - a block executes only when all its inputs are available. Networks execute top to bottom when dependencies allow.

Core Advantages for Pump Control:

Visual representation of signal flow: Critical for Pump Control when handling intermediate control logic

Good for modular programming: Critical for Pump Control when handling intermediate control logic

Reusable components: Critical for Pump Control when handling intermediate control logic

Excellent for process control: Critical for Pump Control when handling intermediate control logic

Good for continuous operations: Critical for Pump Control when handling intermediate control logic

Why Function Blocks Fits Pump Control:

Pump Control systems in Water & Wastewater typically involve:

Sensors: Pressure transmitters for discharge and suction pressure, Flow meters (magnetic, ultrasonic, or vortex), Level transmitters for tank or wet well level

Actuators: Variable frequency drives (VFDs) for speed control, Motor starters (DOL or soft start), Control valves for flow regulation

Complexity: Intermediate with challenges including Preventing cavitation at low suction pressure

Control Strategies for Pump Control:

constant: Maintain fixed speed or output

pressure: PID control to maintain discharge pressure setpoint

flow: PID control to maintain flow rate setpoint

Programming Fundamentals in Function Blocks:

StandardBlocks:
- logic: AND, OR, XOR, NOT - Boolean logic operations
- comparison: EQ, NE, LT, GT, LE, GE - Compare values
- math: ADD, SUB, MUL, DIV, MOD - Arithmetic operations

TimersCounters:
- ton: Timer On-Delay - Output turns ON after preset time
- tof: Timer Off-Delay - Output turns OFF after preset time
- tp: Pulse Timer - Output pulses for preset time

Connections:
- wires: Connect output pins to input pins to pass data
- branches: One output can connect to multiple inputs
- feedback: Outputs can feed back to inputs for state machines

Best Practices for Function Blocks:

Arrange blocks for clear left-to-right data flow

Use consistent spacing and alignment for readability

Label all inputs and outputs with meaningful names

Create custom FBs for frequently repeated logic patterns

Minimize wire crossings by careful block placement

Common Mistakes to Avoid:

Creating feedback loops without proper initialization

Connecting incompatible data types

Not considering execution order dependencies

Overcrowding networks making them hard to read

Typical Applications:

1. HVAC control: Directly applicable to Pump Control
2. Temperature control: Related control patterns
3. Flow control: Related control patterns
4. Batch processing: Related control patterns

Understanding these fundamentals prepares you to implement effective Function Blocks solutions for Pump Control using Unitronics VisiLogic / UniLogic.

Implementing Pump Control with Function Blocks

Pump control systems use PLCs to regulate liquid flow in industrial processes, water treatment, and building services. These systems manage pump operation, protect equipment, optimize energy use, and maintain process parameters.

This walkthrough demonstrates practical implementation using Unitronics VisiLogic / UniLogic and Function Blocks programming.

System Requirements:

A typical Pump Control implementation includes:

Input Devices (Sensors):
1. Pressure transmitters for discharge and suction pressure: Critical for monitoring system state
2. Flow meters (magnetic, ultrasonic, or vortex): Critical for monitoring system state
3. Level transmitters for tank or wet well level: Critical for monitoring system state
4. Temperature sensors for bearing and motor monitoring: Critical for monitoring system state
5. Vibration sensors for predictive maintenance: Critical for monitoring system state

Output Devices (Actuators):
1. Variable frequency drives (VFDs) for speed control: Primary control output
2. Motor starters (DOL or soft start): Supporting control function
3. Control valves for flow regulation: Supporting control function
4. Isolation valves (actuated for remote operation): Supporting control function
5. Check valves to prevent backflow: Supporting control function

Control Equipment:

Centrifugal pumps for high flow applications

Positive displacement pumps for metering

Submersible pumps for wet well applications

Booster pump systems for pressure maintenance

Control Strategies for Pump Control:

constant: Maintain fixed speed or output

pressure: PID control to maintain discharge pressure setpoint

flow: PID control to maintain flow rate setpoint

level: Control tank/wet well level within band

Implementation Steps:

Step 1: Characterize pump curve and system curve

In VisiLogic / UniLogic, characterize pump curve and system curve.

Step 2: Size VFD for application (constant torque vs. variable torque)

In VisiLogic / UniLogic, size vfd for application (constant torque vs. variable torque).

Step 3: Implement primary control loop (pressure, flow, or level)

In VisiLogic / UniLogic, implement primary control loop (pressure, flow, or level).

Step 4: Add pump protection logic (minimum flow, temperature, seal)

In VisiLogic / UniLogic, add pump protection logic (minimum flow, temperature, seal).

Step 5: Program lead/lag sequencing with alternation

In VisiLogic / UniLogic, program lead/lag sequencing with alternation.

Step 6: Implement soft start/stop ramps for smooth operation

In VisiLogic / UniLogic, implement soft start/stop ramps for smooth operation.

Unitronics Function Design:

Function block design in Unitronics uses user-defined FBs in UniLogic (more limited in VisiLogic). Extensive vendor-provided helper FBs cover common tasks (PID, motion, communication, HMI utilities). OEM machine builders typically maintain private FB libraries for their common machine patterns, though code reuse is less mature than in mainstream PLC ecosystems.

Common Challenges and Solutions:

1. Preventing cavitation at low suction pressure

Solution: Function Blocks addresses this through Visual representation of signal flow.

2. Managing minimum flow requirements

Solution: Function Blocks addresses this through Good for modular programming.

3. Coordinating VFD speed with system pressure

Solution: Function Blocks addresses this through Reusable components.

4. Handling pump cycling with varying demand

Solution: Function Blocks addresses this through Excellent for process control.

Safety Considerations:

Dry run protection using flow or level monitoring

Overtemperature protection for motor and bearings

Overload protection through current monitoring

Vibration trips for mechanical failure detection

Emergency stop with proper system depressurization

Performance Metrics:

Scan Time: Optimize for 5 inputs and 5 outputs

Memory Usage: Efficient data structures for Jazz 2 capabilities

Response Time: Meeting Water & Wastewater requirements for Pump Control

Unitronics Diagnostic Tools:

UniLogic (current) and VisiLogic (legacy) integrated debuggers with breakpoints,Built-in simulator covering PLC logic, HMI screens, alarms, recipes, and data tables,Web visualisation for UniStream — remote HMI viewing without additional software,SD card logging with PC-side export tools for offline trend analysis,Modbus RTU/TCP transaction logging built into the IDE,Controller status monitor — CPU load, scan time, memory usage,HMI event logger capturing operator actions for audit purposes,CAN bus diagnostic tools for CANopen-equipped models,Remote support tool — Unitronics' own screen-sharing for technical support,User community forum with active troubleshooting discussions

Unitronics's VisiLogic / UniLogic provides tools for performance monitoring and optimization, essential for achieving the 2-4 weeks development timeline while maintaining code quality.

Unitronics Function Blocks Example for Pump Control

Complete working example demonstrating Function Blocks implementation for Pump Control using Unitronics VisiLogic / UniLogic. Follows Unitronics naming conventions. Tested on Jazz 2 hardware.

(* Unitronics VisiLogic / UniLogic - Pump Control Control *)
(* Reusable Function Blocks Implementation *)
(* Function block design in Unitronics uses user-defined FBs in *)

FUNCTION_BLOCK FB_PUMP_CONTROL_Controller

VAR_INPUT
    bEnable : BOOL;                  (* Enable control *)
    bReset : BOOL;                   (* Fault reset *)
    rProcessValue : REAL;            (* Pressure transmitters for discharge and suction pressure *)
    rSetpoint : REAL := 100.0;  (* Target value *)
    bEmergencyStop : BOOL;           (* Safety input *)
END_VAR

VAR_OUTPUT
    rControlOutput : REAL;           (* Variable frequency drives (VFDs) for speed control *)
    bRunning : BOOL;                 (* Process active *)
    bComplete : BOOL;                (* Cycle complete *)
    bFault : BOOL;                   (* Fault status *)
    nFaultCode : INT;                (* Diagnostic code *)
END_VAR

VAR
    (* Internal Function Blocks *)
    fbSafety : FB_SafetyMonitor;     (* Safety logic *)
    fbRamp : FB_RampGenerator;       (* Soft start/stop *)
    fbPID : FB_PIDController;        (* Process control *)
    fbDiag : FB_Diagnostics;         (* Alarm handling uses UniLogic's built-in Alarm Manager — configure alarm conditions in tables with severity, message text, and logging behaviour, and the engine handles detection, acknowledgement, history, and HMI display without custom code. VisiLogic uses a simpler alarm approach via HMI event handlers. *)

    (* Internal State *)
    eInternalState : E_ControlState;
    tonWatchdog : TON;
END_VAR

(* Safety Monitor - Dry run protection using flow or level monitoring *)
fbSafety(
    Enable := bEnable,
    EmergencyStop := bEmergencyStop,
    ProcessValue := rProcessValue,
    HighLimit := rSetpoint * 1.2,
    LowLimit := rSetpoint * 0.1
);

(* Main Control Logic *)
IF fbSafety.SafeToRun THEN
    (* Ramp Generator - Prevents startup surge *)
    fbRamp(
        Enable := bEnable,
        TargetValue := rSetpoint,
        RampRate := 20.0,  (* Water & Wastewater rate *)
        CurrentValue => rSetpoint
    );

    (* PID Controller - Process regulation *)
    fbPID(
        Enable := fbRamp.InPosition,
        ProcessValue := rProcessValue,
        Setpoint := fbRamp.CurrentValue,
        Kp := 1.0,
        Ki := 0.1,
        Kd := 0.05,
        OutputMin := 0.0,
        OutputMax := 100.0
    );

    rControlOutput := fbPID.Output;
    bRunning := TRUE;
    bFault := FALSE;
    nFaultCode := 0;

ELSE
    (* Safe State - Overtemperature protection for motor and bearings *)
    rControlOutput := 0.0;
    bRunning := FALSE;
    bFault := NOT bEnable;  (* Only fault if not intentional stop *)
    nFaultCode := fbSafety.FaultCode;
END_IF;

(* Diagnostics - Data logging uses UniLogic's Data Samplers — configured triggers (time-based or event-based) write structured records to Data Tables or SD card in CSV format. Exported files can be pushed via FTP or email. For cloud integration, UniCloud provides managed data ingestion. Simpler VisiLogic projects use HMI-triggered SD writes via custom ladder code. *)
fbDiag(
    ProcessRunning := bRunning,
    FaultActive := bFault,
    ProcessValue := rProcessValue,
    ControlOutput := rControlOutput
);

(* Watchdog - Detects frozen control *)
tonWatchdog(IN := bRunning AND NOT fbPID.OutputChanging, PT := T#10S);
IF tonWatchdog.Q THEN
    bFault := TRUE;
    nFaultCode := 99;  (* Watchdog fault *)
END_IF;

(* Reset Logic *)
IF bReset AND NOT bEmergencyStop THEN
    bFault := FALSE;
    nFaultCode := 0;
    fbDiag.ClearAlarms();
END_IF;

END_FUNCTION_BLOCK

Code Explanation:

1.Encapsulated function block follows Function block design in Unitronics uses - reusable across Water & Wastewater projects
2.FB_SafetyMonitor provides Dry run protection using flow or level monitoring including high/low limits
3.FB_RampGenerator prevents startup issues common in Pump Control systems
4.FB_PIDController tuned for Water & Wastewater: Kp=1.0, Ki=0.1
5.Watchdog timer detects frozen control - critical for intermediate Pump Control reliability
6.Diagnostic function block enables Data logging uses UniLogic's Data Samplers — configured triggers (time-based or event-based) write structured records to Data Tables or SD card in CSV format. Exported files can be pushed via FTP or email. For cloud integration, UniCloud provides managed data ingestion. Simpler VisiLogic projects use HMI-triggered SD writes via custom ladder code. and Alarm handling uses UniLogic's built-in Alarm Manager — configure alarm conditions in tables with severity, message text, and logging behaviour, and the engine handles detection, acknowledgement, history, and HMI display without custom code. VisiLogic uses a simpler alarm approach via HMI event handlers.

Best Practices

✓Follow Unitronics naming conventions: Unitronics projects use IDE-managed tag names rather than raw memory addressing.
✓Unitronics function design: Function block design in Unitronics uses user-defined FBs in UniLogic (more limi
✓Data organization: Unitronics uses its own tag database concept rather than IEC-standard data block
✓Function Blocks: Arrange blocks for clear left-to-right data flow
✓Function Blocks: Use consistent spacing and alignment for readability
✓Function Blocks: Label all inputs and outputs with meaningful names
✓Pump Control: Use PID with derivative on PV for pressure control
✓Pump Control: Implement soft start ramps even with VFD (200-500ms)
✓Pump Control: Add flow proving before considering pump operational
✓Debug with VisiLogic / UniLogic: Use the built-in simulator to reproduce issues before hardware visit
✓Safety: Dry run protection using flow or level monitoring
✓Use VisiLogic / UniLogic simulation tools to test Pump Control logic before deployment

Common Pitfalls to Avoid

⚠Function Blocks: Creating feedback loops without proper initialization
⚠Function Blocks: Connecting incompatible data types
⚠Function Blocks: Not considering execution order dependencies
⚠Unitronics common error: VisiLogic-to-UniLogic migration issues — not all projects convert cleanly
⚠Pump Control: Preventing cavitation at low suction pressure
⚠Pump Control: Managing minimum flow requirements
⚠Neglecting to validate Pressure transmitters for discharge and suction pressure leads to control errors
⚠Insufficient comments make Function Blocks programs unmaintainable over time

Related Certifications

🏆Unitronics Certified Integrator

🏆UniLogic Developer Training

🏆Advanced Unitronics Programming Certification

Mastering Function Blocks for Pump Control applications using Unitronics VisiLogic / UniLogic requires understanding both the platform's capabilities and the specific demands of Water & Wastewater. This guide has provided comprehensive coverage of implementation strategies, working code examples, best practices, and common pitfalls to help you succeed with intermediate Pump Control projects.

Unitronics's 1% market share and moderate - us small-integrator market, oem machines, building automation demonstrate the platform's capability for demanding applications. The platform excels in Water & Wastewater applications where Pump Control reliability is critical.

By following the practices outlined in this guide—from proper program structure and Function Blocks best practices to Unitronics-specific optimizations—you can deliver reliable Pump Control systems that meet Water & Wastewater requirements.

Next Steps for Professional Development:

1. Certification: Pursue Unitronics Certified Integrator to validate your Unitronics expertise
2. Advanced Training: Consider UniLogic Developer Training for specialized Water & Wastewater applications
3. Hands-on Practice: Build Pump Control projects using Jazz 2 hardware
4. Stay Current: Follow VisiLogic / UniLogic updates and new Function Blocks features

Function Blocks Foundation:

Function Block Diagram (FBD) is a graphical programming language where functions and function blocks are represented as boxes connected by signal line...

The 2-4 weeks typical timeline for Pump Control projects will decrease as you gain experience with these patterns and techniques. Remember: Use PID with derivative on PV for pressure control

For further learning, explore related topics including Temperature control, Wastewater treatment, and Unitronics platform-specific features for Pump Control optimization.