Digital inputs and outputs
Цель: Изучить тему «Digital inputs and outputs» и закрепить её практическими заданиями и самопроверкой.
2 акад. часа чтение и разбор теории, решение задач, работа со схемой или виртуальным стендом и проверка понимания.
Основной материал
Digital input converts field electrical state into logical 0/1. Typical industrial signals use 24 VDC, though other levels exist. Input module may have optical isolation, filters and group commons.
Digital output controls load through transistor, relay or triac. Transistor outputs are fast and suitable DC; relay can switch AC/DC but slower and wears mechanically; triac used AC.
Sourcing/sinking
PNP/NPN concepts describe current direction and sensor/output topology. Misunderstanding sourcing/sinking is a common commissioning problem. Always use wiring diagram and common reference.
Protection
Inductive loads generate voltage spikes. Flyback diode or suppression network protects transistor/relais contacts. PLC output often drives interposing relay rather than large contactor coil directly, depending rating and design.
Практическая работа
Draw 24 VDC input circuit for proximity sensor and output circuit driving interposing relay coil with flyback diode. Label current path.
Самопроверка
• What does DI module do?
• Difference transistor vs relay output?
• What is PNP/NPN?
• Why inductive suppression?
• Why use interposing relay?
Что нужно запомнить
- Digital input converts field electrical state into logical 0/1.
- Typical industrial signals use 24 VDC, though other levels exist.
- Input module may have optical isolation, filters and group commons.
- Digital output controls load through transistor, relay or triac.
- Transistor outputs are fast and suitable DC; relay can switch AC/DC but slower and wears mechanically; triac used AC.