Learning to implement Counters for Safety Systems using Unitronics's VisiLogic / UniLogic is an essential skill for PLC programmers working in Universal. This comprehensive guide walks you through the fundamentals, providing clear explanations and practical examples that you can apply immediately to real-world projects.
Unitronics has established itself as Moderate - US small-integrator market, OEM machines, building automation, making it a strategic choice for Safety Systems applications. With 1% global market share and 6 popular PLC families including the Jazz 2 and Samba 7", Unitronics provides the robust platform needed for advanced complexity projects like Safety Systems.
The Counters approach is particularly well-suited for Safety Systems because counting parts, cycles, events, or maintaining production totals. This combination allows you to leverage essential for production tracking while managing the typical challenges of Safety Systems, including safety integrity level (sil) compliance and redundancy requirements.
Throughout this guide, you'll discover step-by-step implementation strategies, working code examples tested on VisiLogic / UniLogic, and industry best practices specific to Universal. Whether you're programming your first Safety Systems system or transitioning from another PLC platform, this guide provides the practical knowledge you need to succeed with Unitronics Counters programming.
Unitronics VisiLogic / UniLogic for Safety Systems
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 Safety Systems:
- 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 Safety Systems 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 Safety Systems systems, including Safety light curtains, Emergency stop buttons, Safety door switches.
Control Equipment for Safety Systems:
- Safety PLCs (fail-safe controllers)
- Safety relays (configurable or fixed)
- Safety I/O modules with diagnostics
- Safety network protocols (PROFIsafe, CIP Safety)
Unitronics's controller families for Safety Systems include:
- Jazz 2: Suitable for advanced Safety Systems applications
- Samba 7": Suitable for advanced Safety Systems applications
- Vision V350: Suitable for advanced Safety Systems applications
- Vision V570: Suitable for advanced Safety Systems 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 Safety Systems projects requiring advanced skill levels and 4-8 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.
Understanding Counters for Safety Systems
PLC counters track the number of events or items. They increment or decrement on input transitions and compare against preset values.
Execution Model:
For Safety Systems applications, Counters offers significant advantages when counting parts, cycles, events, or maintaining production totals.
Core Advantages for Safety Systems:
- Essential for production tracking: Critical for Safety Systems when handling advanced control logic
- Simple to implement: Critical for Safety Systems when handling advanced control logic
- Reliable and accurate: Critical for Safety Systems when handling advanced control logic
- Easy to understand: Critical for Safety Systems when handling advanced control logic
- Widely used: Critical for Safety Systems when handling advanced control logic
Why Counters Fits Safety Systems:
Safety Systems systems in Universal typically involve:
- Sensors: Emergency stop buttons (Category 0 or 1 stop), Safety light curtains (Type 2 or Type 4), Safety laser scanners for zone detection
- Actuators: Safety contactors (mirror contact type), Safe torque off (STO) drives, Safety brake modules
- Complexity: Advanced with challenges including Achieving required safety level with practical architecture
Programming Fundamentals in Counters:
Counters in VisiLogic / UniLogic follows these key principles:
1. Structure: Counters organizes code with simple to implement
2. Execution: Scan cycle integration ensures 5 sensor inputs are processed reliably
3. Data Handling: Proper data types for 4 actuator control signals
Best Practices for Counters:
- Debounce mechanical switch inputs before counting
- Use high-speed counters for pulses faster than scan time
- Implement overflow detection for long-running counters
- Store counts to retentive memory if needed across power cycles
- Add counter values to HMI for operator visibility
Common Mistakes to Avoid:
- Counting level instead of edge - multiple counts from one event
- Not debouncing noisy inputs causing false counts
- Using standard counters for high-speed applications
- Integer overflow causing count wrap-around
Typical Applications:
1. Bottle counting: Directly applicable to Safety Systems
2. Conveyor tracking: Related control patterns
3. Production totals: Related control patterns
4. Batch counting: Related control patterns
Understanding these fundamentals prepares you to implement effective Counters solutions for Safety Systems using Unitronics VisiLogic / UniLogic.
Implementing Safety Systems with Counters
Safety system control uses safety-rated PLCs and components to protect personnel and equipment from hazardous conditions. These systems implement safety functions per IEC 62443 and ISO 13849 standards with redundancy and diagnostics.
This walkthrough demonstrates practical implementation using Unitronics VisiLogic / UniLogic and Counters programming.
System Requirements:
A typical Safety Systems implementation includes:
Input Devices (Sensors):
1. Emergency stop buttons (Category 0 or 1 stop): Critical for monitoring system state
2. Safety light curtains (Type 2 or Type 4): Critical for monitoring system state
3. Safety laser scanners for zone detection: Critical for monitoring system state
4. Safety interlock switches (tongue, hinged, trapped key): Critical for monitoring system state
5. Safety mats and edges: Critical for monitoring system state
Output Devices (Actuators):
1. Safety contactors (mirror contact type): Primary control output
2. Safe torque off (STO) drives: Supporting control function
3. Safety brake modules: Supporting control function
4. Lock-out valve manifolds: Supporting control function
5. Safety relay outputs: Supporting control function
Control Equipment:
- Safety PLCs (fail-safe controllers)
- Safety relays (configurable or fixed)
- Safety I/O modules with diagnostics
- Safety network protocols (PROFIsafe, CIP Safety)
Control Strategies for Safety Systems:
1. Primary Control: Safety-rated PLC programming for personnel protection, emergency stops, and safety interlocks per IEC 61508/61511.
2. Safety Interlocks: Preventing Safety integrity level (SIL) compliance
3. Error Recovery: Handling Redundancy requirements
Implementation Steps:
Step 1: Perform hazard analysis and risk assessment
In VisiLogic / UniLogic, perform hazard analysis and risk assessment.
Step 2: Determine required safety level (SIL/PL) for each function
In VisiLogic / UniLogic, determine required safety level (sil/pl) for each function.
Step 3: Select certified safety components meeting requirements
In VisiLogic / UniLogic, select certified safety components meeting requirements.
Step 4: Design safety circuit architecture per category requirements
In VisiLogic / UniLogic, design safety circuit architecture per category requirements.
Step 5: Implement safety logic in certified safety PLC/relay
In VisiLogic / UniLogic, implement safety logic in certified safety plc/relay.
Step 6: Add diagnostics and proof test provisions
In VisiLogic / UniLogic, add diagnostics and proof test provisions.
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. Achieving required safety level with practical architecture
- Solution: Counters addresses this through Essential for production tracking.
2. Managing nuisance trips while maintaining safety
- Solution: Counters addresses this through Simple to implement.
3. Integrating safety with production efficiency
- Solution: Counters addresses this through Reliable and accurate.
4. Documenting compliance with multiple standards
- Solution: Counters addresses this through Easy to understand.
Safety Considerations:
- Use only certified safety components and PLCs
- Implement dual-channel monitoring per category requirements
- Add diagnostic coverage to detect latent faults
- Design for fail-safe operation (de-energize to trip)
- Provide regular proof testing of safety functions
Performance Metrics:
- Scan Time: Optimize for 5 inputs and 4 outputs
- Memory Usage: Efficient data structures for Jazz 2 capabilities
- Response Time: Meeting Universal requirements for Safety Systems
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 4-8 weeks development timeline while maintaining code quality.
Unitronics Counters Example for Safety Systems
Complete working example demonstrating Counters implementation for Safety Systems using Unitronics VisiLogic / UniLogic. Follows Unitronics naming conventions. Tested on Jazz 2 hardware.
// Unitronics VisiLogic / UniLogic - Safety Systems Control
// Counters Implementation for Universal
// Unitronics projects use IDE-managed tag names rather than ra
// ============================================
// Variable Declarations
// ============================================
VAR
bEnable : BOOL := FALSE;
bEmergencyStop : BOOL := FALSE;
rSafetylightcurtains : REAL;
rSafetyrelays : REAL;
END_VAR
// ============================================
// Input Conditioning - Emergency stop buttons (Category 0 or 1 stop)
// ============================================
// Standard input processing
IF rSafetylightcurtains > 0.0 THEN
bEnable := TRUE;
END_IF;
// ============================================
// Safety Interlock - Use only certified safety components and PLCs
// ============================================
IF bEmergencyStop THEN
rSafetyrelays := 0.0;
bEnable := FALSE;
END_IF;
// ============================================
// Main Safety Systems Control Logic
// ============================================
IF bEnable AND NOT bEmergencyStop THEN
// Safety system control uses safety-rated PLCs and components
rSafetyrelays := rSafetylightcurtains * 1.0;
// Process monitoring
// Add specific control logic here
ELSE
rSafetyrelays := 0.0;
END_IF;Code Explanation:
- 1.Counters structure optimized for Safety Systems in Universal applications
- 2.Input conditioning handles Emergency stop buttons (Category 0 or 1 stop) signals
- 3.Safety interlock ensures Use only certified safety components and PLCs always takes priority
- 4.Main control implements Safety system control uses safety-rated
- 5.Code runs every scan cycle on Jazz 2 (typically 5-20ms)
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
- ✓Counters: Debounce mechanical switch inputs before counting
- ✓Counters: Use high-speed counters for pulses faster than scan time
- ✓Counters: Implement overflow detection for long-running counters
- ✓Safety Systems: Keep safety logic simple and auditable
- ✓Safety Systems: Use certified function blocks from safety PLC vendor
- ✓Safety Systems: Implement cross-monitoring between channels
- ✓Debug with VisiLogic / UniLogic: Use the built-in simulator to reproduce issues before hardware visit
- ✓Safety: Use only certified safety components and PLCs
- ✓Use VisiLogic / UniLogic simulation tools to test Safety Systems logic before deployment
Common Pitfalls to Avoid
- ⚠Counters: Counting level instead of edge - multiple counts from one event
- ⚠Counters: Not debouncing noisy inputs causing false counts
- ⚠Counters: Using standard counters for high-speed applications
- ⚠Unitronics common error: VisiLogic-to-UniLogic migration issues — not all projects convert cleanly
- ⚠Safety Systems: Achieving required safety level with practical architecture
- ⚠Safety Systems: Managing nuisance trips while maintaining safety
- ⚠Neglecting to validate Emergency stop buttons (Category 0 or 1 stop) leads to control errors
- ⚠Insufficient comments make Counters programs unmaintainable over time
Related Certifications
Mastering Counters for Safety Systems applications using Unitronics VisiLogic / UniLogic requires understanding both the platform's capabilities and the specific demands of Universal. This guide has provided comprehensive coverage of implementation strategies, working code examples, best practices, and common pitfalls to help you succeed with advanced Safety Systems 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 Universal applications where Safety Systems reliability is critical.
By following the practices outlined in this guide—from proper program structure and Counters best practices to Unitronics-specific optimizations—you can deliver reliable Safety Systems systems that meet Universal 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 Universal applications
3. Hands-on Practice: Build Safety Systems projects using Jazz 2 hardware
4. Stay Current: Follow VisiLogic / UniLogic updates and new Counters features
Counters Foundation:
PLC counters track the number of events or items. They increment or decrement on input transitions and compare against preset values....
The 4-8 weeks typical timeline for Safety Systems projects will decrease as you gain experience with these patterns and techniques. Remember: Keep safety logic simple and auditable
For further learning, explore related topics including Conveyor tracking, Emergency stop systems, and Unitronics platform-specific features for Safety Systems optimization.