PLC and PLR Concepts from Real-World Class Transcript

Project Updates and Real-World Context

  • Eye clinic project
    • Final inspection occurred on Tuesday; inspector requested a couple more exit signs not in the plan.
    • Ended up deviating from the plan and adding signs/walls that weren’t on the original drawings.
    • Owner wants track lighting added later; site is a good customer; they also provide eyewear discounts.
    • The speaker will return to add track lights and address inspections/CEO approvals as needed.
  • Ice factory service upgrade project
    • Ongoing project with Excel on a long-running service upgrade; first meeting for the surface up service upgrade was in November (roughly nine months ago).
    • Typical time frame for such changes is about a year; some delays due to project pacing, but progress has been steady.
    • Cable tray/underground coffin between transformer and secondary connection cabinet for a secondary connection cabinet system was installed; the coffin is a large concrete block (~2 ft deep, ~2 ft wide, ~8 ft long).
    • Transformer installed last Friday; goal is to complete interior wiring before everything is locked up.
    • Friday work involved using Simple Reeler to pull wire; three runs of three hundred feet each, and three runs of five hundred feet each (i.e., six runs total with various lengths).
    • Simple Reeler (Southwire) is highlighted as a major productivity gain for pulling wire; no jack stands required; can be forklift-supported on-site.
    • Vacuuming/jet line and lubrication process used to thread wire through conduit; multi-person coordination (typically three people) to pull runs.
    • A note on cost-efficiency: Simple Reelers may be rented via CED; unit price around $60 new; rental recommended for cost savings on larger pulls.
    • Alternative methods include crimp-on pull heads and disposable socks; crimped pull heads can be used to speed pulls, especially on copper/aluminum runs; socks (iTool socks) are long (roughly 4–6 ft) and can dig into the wire if not used with a proper tugger system.
    • Tools and gear discussion: Milwaukee fish tape puller (M18) with steel drum is highly praised for extending reach; drums are replaceable but can kink; fiberglass/nonconductive drums exist; Greenlee handheld tugger as another option.
    • Project management approach: time savings on labor are a major driver; apprentices and older methods are less preferred; emphasis on equipment investments reducing labor hours.
    • Current status: completed Friday pulls; remaining work includes making up the secondary connection cabinet, disconnects, and grounds, plus testing and service inspections; CT meter enclosure and CTs are pending from Excel and may affect inspection timing.
  • General reflections on work and tools
    • The speaker has shifted away from hand-pulling everything to using powered tools and pullers; prioritizes efficiency and worker safety.
    • Passion for tool investment as a cost-saver and time-saver, with a practical stance on when to use different pulling methods.
    • Emphasis on documenting and sharing gear recommendations with peers, including where to source gear and how to use it effectively.
  • Class logistics and personal anecdotes
    • Opening segments include casual check-ins, updates on personal/week activities (fishing, movies, etc.).
    • Homework and quiz structure described; class uses a “homework review” followed by a quiz (20 questions) to keep a consistent pace and percentage weight per question.
    • Banked question pools for quizzes; first-semester pool is smaller, so answers should be recorded because questions can recur in exams.
    • Reminder to wait for record button before typing in the chat; the log may save after recording begins.
    • Introduction to PLCs and relays; emphasis on TICO SG2 PLR (free software) for introductory hands-on work; labs emphasize ladder logic and simple PLC concepts before moving to full PLC programming next week.
  • Ethical and practical considerations
    • Acknowledge that some questions in reviews may be flawed or require clarification; instructor commits to addressing issues and helping students work through discrepancies.
    • Emphasis on safety, proper startup/shutdown procedures, and adherence to regulations when working with electrical systems and hazardous materials.
  • Real-world relevance and ongoing learning
    • PLCs and PLRs are introduced as foundational for automating industrial control; examples include elevator relay banks evolving to PLCs; the role of PLCs in building automation and process control.
    • Introduction to how PLCs interface with sensors (digital vs analog), actuators, and communication networks (Modbus, LAN); practical examples include light control, boilers, and HVAC optimization with PID control.
    • Concepts such as sunsetting old relay banks, using memory devices (M relays), and the value of reprogrammable software over physical rewiring are highlighted for efficiency and maintainability.

PLC Fundamentals: What a PLC and a PLC Relays (PLR) Do

  • Definitions and context
    • PLC: Programmable Logic Controller; used to monitor and control industrial-type circuits with a CPU, input section, and output section; stores program and can be reprogrammed.
    • PLR: Programmable Logic Relay; the smaller, cheaper cousin of a PLC, with built-in CPU and relays inside a single box; suitable for smaller applications.
    • Primary difference: hardware configurability and software-driven logic rather than hardwired relay banks.
  • Hardware components and architecture
    • Core components: Power supply, CPU, input section, output section.
    • Inputs: Digital (I1–I6) and cursor inputs; analog inputs may exist via modules; field inputs vs software-generated contacts.
    • Outputs: Relay outputs (Q1–Q4), potential transistor outputs for signaling (not load-bearing), and possibly analog outputs (0–10 V, 4–20 mA in expansion cards).
    • Additional pieces: Battery/power for reliability, optional HMI display, real-time clock, expansion modules, Modbus/LAN for remote communication.
    • Memory/logic elements: Internally stored memory relays (retentive and non-retentive), counters, timers, and software-generated contacts.
  • PLC vs PLR basics
    • PLCs offer more robust software ecosystems, more I/O, and more complex control strategies (BAS, machines, etc.).
    • PLRs provide a compact, low-cost entry point with enough functionality (timers, counters, memory, simple ladder logic).
  • Basic operation flow
    • Four-stage concept (typical PLC cycle):
    • Input scan: Detect the state of inputs (sensors, switches).
    • Program scan: Execute the stored logic to determine outputs.
    • Output update: Update output devices to reflect the results.
    • Housekeeping: Self-diagnostics, communications, updates, and reporting.
    • Scan time considerations
    • Analog inputs generally take longer to process than digital inputs.
    • Example ranges: fast systems (e.g., water tank control) around the order of a few milliseconds; slower systems (e.g., room temperature) around tens to hundreds of milliseconds.
  • Input types and signal handling
    • Digital inputs: On/off states from switches, sensors; discrete signals.
    • Analog inputs: Sensors with a range (0–100% scale via voltage or current); require scaling in software.
    • Thresholds for digital interpretation (as discussed in SG2 PLR context):
    • Logical 0: 0–$40$ V (AC) interpreted as 0.
    • Logical 1: $79$–$120$ V (AC) interpreted as 1.
    • 40–79 V are considered invalid for digital inputs on these modules.
  • Interface, communication, and expansion
    • PLCs/PLRs may include Modbus, LAN, and other communication interfaces for remote control and monitoring.
    • Expansion cards allow additional digital/analog outputs, analog signaling, and communication capabilities.
  • Practical and educational implications
    • PLCs consolidate complex control logic into software, enabling rapid reprogramming and easier fault finding.
    • Memory and timer/counter functionality enable sophisticated control schemes (e.g., start/stop memory circuits, PID control for valves).
    • The ability to clone programs across multiple PLC units saves time in large installations.
  • Example control concepts illustrated in class
    • Normally open vs normally closed inputs and how a PLC can emulate either behavior by programming the coil logic and holding contacts.
    • Start/stop memory circuit: a classic ladder logic pattern using an internal memory relay (M) for holding a rung; a stop button can break the holding circuit to stop the motor.
    • Timer use cases: on-delay timers (TO), flash timers for warnings, and how timers can be used to sequence actions after a trigger.
    • Use of an internal memory relay (M) for holding state or creating a latch, allowing simple control loops without external relays.
  • Observations on electronics and safety
    • Emphasis on proper startup/shutdown sequences to avoid hazardous conditions when programming or testing PLCs in a live environment.
    • Warnings about using the front-panel buttons for programming; recommended practice is to use the companion software for programming tasks.

TECO SG2 PLR Deep Dive: Hardware, Software, and Programming Concepts

  • Product overview and targeting
    • TECO SG2 PLR: a third-generation programmable logic relay; affordable, compact, and capable for small projects.
    • Focus in class is on the SG2 10/4 model (10 inputs/outputs; 6 inputs, 4 outputs) with a built-in display and keypad.
    • Variants include different input power ranges and output types; some units support DC inputs, others AC inputs; common configurations include DC 12/24 V or AC 100–240 V supplies.
  • Special fields in part numbers and what they mean
    • Part numbers identify: number of I/O points, form factor, output type, and input power range.
    • Example model: SG2 ten HRA has 10 I/O points (I1–I6 inputs, Q outputs), a built-in display, and coil types that are electromechanical relays with AC operation.
  • Input and output specifics
    • Inputs (I1–I6): digital, AC input interpretation rules (0 vs 1 within defined thresholds); inputs can be wired to normally open (NO) or normally closed (NC) devices; the software can override physical behavior by logic.
    • Outputs (Q1–Q4): electromechanical relays capable of energizing outputs like pilot lamps; in some models, transistor outputs may be available for signaling rather than loading.
    • Optional sensors: temperature modules, analog inputs, and HMI display; HMI is not recommended for direct programming but can be used for display purposes.
  • Programming and software ecosystem
    • The SG2 PLR is programmed via TECO SG2 client software (free) and a USB connection to a PC; programming is done using ladder logic, functional blocks, and parameter settings.
    • The on-device LCD with four cursor buttons (Escape, Delete, Select, and a Run/Stop control) allows basic programming directly on the device, but this is not recommended for heavy programming tasks.
    • The device supports a ladder language with up to 300 rungs; it also supports function blocks, timers, counters, real-time clock, PID, and various mathematical instructions.
  • Programming concepts and examples
    • Ladder logic basics: rungs with contacts on the left and a coil on the right; a rung can have up to three contacts in a row, but more can be added via additional rungs.
    • Terminal inputs (I1–I6) vs software-generated contacts (auxiliary relays, timers, counters, etc.).
    • Memory concepts: retentive vs nonretentive auxiliary relays (31 each); memory states persist when power is removed for retentive mem relays.
    • Software-generated contacts track coil states; coil changes reflect in the corresponding contacts, enabling dynamic logic within the ladder diagram.
  • Demonstrations and capabilities shown in the lecture
    • Hands-on demonstration of building a start/stop memory circuit using an internal memory relay (M) and Q outputs; the coach shows how to wire NO NC inputs and connect holding contacts to create a latch for motor control.
    • Real-time editing and beaming of programs to the PLR (via software), including creating, updating, and running the ladder logic on the device, plus a lab view that shows the LED indicators for inputs and outputs.
    • Simulation mode: ability to run the program in software without live hardware; pink lines indicate broken continuity and help diagnose wiring logic.
    • Example of using a timer to flash a warning light before motor start and then starting the motor after a defined delay; demonstrates how to break the flashing loop with an additional memory relay and a second timer to coordinate actions.
    • A start/stop memory block that demonstrates how to design a latch with a hold contact in parallel with the load; use of M and Q contacts to hold a circuit state.
    • Emphasis on avoiding using the device’s tiny on-board screen for programming due to usability challenges; prefer PC-based programming for complex tasks.
  • Lab activities and learning resources
    • Encouragement to download TECO SG2 software and practice along; TECO SG2 client software is free and suitable for beginners.
    • Supplemental videos from Engineering Mindset and Jim Pytel (Big Bad Tech) used to explain PLC concepts, with downloadable links in LMS for extended learning.
    • Additional lab resources include a TECO SG2 PLR hardware demo with a 4-20 mA/0-10 V analog option, a built-in HMI, and expansion modules for more IO and features.
  • Practical takeaways and implications
    • SG2 PLR provides a compact, cost-effective entry point for learning PLC concepts without expensive hardware; supports a robust set of instructions and 300 ladder rungs, making it sufficient for introductory and some intermediate projects.
    • The software-based approach to control logic enables rapid prototyping, testing, and deployment across multiple devices, with minimal hardware changes.
    • Real-world caveats highlighted include the importance of not programming on the small screen, being mindful of wiring and input signal ranges, and the value of using the software environment for complex logic.

Input/Output Fundamentals: Digital vs Analog, and Signal Conditioning

  • Digital (discrete) inputs
    • Represent simple on/off states (0/1); used for push buttons, limit switches, occupancy sensors, etc.
    • In SG2 PLR context, digital inputs are interpreted with thresholds (0 as 0–$40$ V AC, 1 as $79$–$120$ V AC); 40–79 V are invalid as digital inputs.
  • Analog inputs
    • Provide a range of values (e.g., temperature sensors, pressure sensors, thermocouples, RTDs).
    • PLCs/PLRs scale/convert voltage or current into digital counts for the CPU to process.
  • Output types
    • Relay outputs: can switch higher loads (e.g., lights, motors, actuators); robust and widely used in PLC control.
    • Transistor/solid-state outputs: better for signaling or lower-load control; not always suitable for directly driving motors.
    • Analog outputs (when present): provide 0–10 V, 4–20 mA signals for precise control (e.g., valve position or VFD control).
  • Signal conditioning and isolation
    • Inputs isolate the PLC from fluctuations and ensure clean signals; signals are conditioned before reaching the CPU.
  • Core PLC execution model (revisited)
    • Input scan, program scan, execute logic, update outputs, housekeeping; scan time is a function of input type, CPU speed, and program complexity.

Quizzes, Homework, and Class Mechanics

  • Homework review structure
    • Each class starts with homework review; questions may come from a small bank in the first semester.
    • Answers should be recorded because early questions may reappear on quizzes/tests.
    • If a member has a concern about a question, the instructor invites PMs or emails for clarification.
  • Quiz setup and expectations
    • Quizzes are housed under lesson four zero two (402) in the LMS; quiz one is a single-attempt assessment with a 35–40 minute time window depending on script settings.
    • The instructor uses a 20-question format to keep per-question weight reasonable (5% per question visually, if there are 20 questions).
    • The quiz will reuse questions from the homework banks; some questions may be repeated in exams, so recording answers is important.
  • Bank and content notes
    • Bank depth is limited (examples show 32 questions deep for 401-level content historically);
    • Students are encouraged to download and use the TI/SG2 software and refer to the FactoryMation site for the software download to stay aligned with course content.
  • Class pacing and expectations
    • The course aims to cover futures/options in early weeks; PLC programming topics intensify in later weeks.
    • Students are encouraged to ask questions if something is unclear; instructor promises to address concerns and provide additional help as needed.

Safety, Compliance, and Best Practice

  • OSHA and hazard considerations
    • Safety information highlighted, including flammable and combustible liquid handling under CFR 1926.152; details include appropriate storage limits, bonding, and fire safety equipment placement.
    • Key points from the CFR include: storage limits by liquid type (gallons per cabinet or room), bonding when transferring liquids, and minimum extinguisher placement (20-B rated extinguishers within 10 feet of certain liquid storage and 25–75 feet from liquid storage areas).
    • Additional rules cover outdoor storage distance (e.g., 20 feet from buildings) and access to fire apparatus, as well as ensuring exits and paths remain clear.
  • Practical safety notes from the PLC lab
    • Emphasis on step-by-step startup/shutdown protocols for hardware like PLCs and VFDs to avoid hazardous conditions.
    • Always verify program stability and maintain clear, safe working areas when testing ladder logic on live hardware.

Real-World Applications and Takeaways

  • Automation and control concepts in practice
    • PLCs/PLRs underpin automation across industries: building management systems, manufacturing lines, packaging, etc.
    • The progression from relay banks to PLCs represents a shift from hard-wired logic to software-driven control, enabling easier maintenance and more flexible operations.
  • Learning trajectory and resources
    • Students are encouraged to explore TECO SG2 PLR hardware/software, watch related PLC videos (Engineering Mindset, Big Bad Tech), and engage with online resources like FactoryMation for software downloads.
  • Personal and professional growth themes
    • Emphasis on investing in proper tooling to save time, reduce worker strain, and improve site safety.
    • The instructor stresses practical learning through hands-on experiments, simulations, and real-world project examples to bridge theory and field work.

Quick Reference: Key Figures, Terms, and Concepts Mentioned

  • Equipment and products
    • Simple Reeler (Southwire): used to spool and pull wire; can be rented; typical price around $60 new.
    • Milwaukee fish tape puller (M18): automated wire feeding/retrieval; replaceable drums; nonconductive variants available; best used with caution on smaller diameter wires.
    • Greenlee handheld tugger: compact, manual pulling aid; handy for short pulls.
    • Socks (iTool socks): long compression socks used with wire pulling; can dig into the wire if not paired with a proper tugger system.
  • Service upgrade specifics
    • Underground coffin (cable tray): concrete structure used to house conduits between transformer and secondary cabinet; dimensions approximately 2 ft x 2 ft x 8 ft.
    • Transformer: installed and wired as part of the upgrade; subsequent steps include wiring and testing.
  • PLC and PLR details (SG2 PLR)
    • SG2 PLR models: 10 inputs/4 outputs in the example; 12/24 V DC or 85–240 V AC options depending on model; built-in LCD screen and keypad on some models.
    • Memory and instructions: up to 31 retentive aux relays, 31 nonretentive aux relays; 260 function block instructions; 126 internal auxiliary instructions; 31 timers; 31 real-time clock instructions; 15 PID instructions; 62 math instructions; 15 analog ramp instructions; 2 PWM instructions; 240 data registers; 300 ladder rungs.
    • Programming schemes: ladder logic; function blocks; parameters; software-generated contacts; ability to emulate normally open/normally closed devices by software logic.
  • Signals and standards
    • Digital inputs thresholds for AC signals: 0–$40$ V → logical 0; $79$–$120$ V → logical 1; 40–79 V invalid.
    • Output ranges and load considerations: relay outputs capable of controlling loads; transistor outputs for signaling; analog outputs possible with expansion modules.
    • Safety and standards references for hazardous liquids use (CFR 1926.152) and firefighting equipment guidelines (extinguisher ratings, placement rules).

Note on Structure for Exam-Ready Notes

  • The notes above are organized by major themes (projects, PLC fundamentals, TECO SG2 PLR specifics, lab activities, safety, and class logistics).
  • Each section includes the core ideas, practical examples, and real-world connections to help you study and recall details during exams.
  • If you want these notes in a different format (condensed cheat-sheet, concept map, or glossary), tell me and I can reformat accordingly.