CONTROLADORES LOGICOS PROGRAMABLES

Qué es un PLC CONTROLADOR PROGRAMABLE INPUTS OUTPUTS CR Originated from a General Motors Specification for a reprogrammable control device that could be used in place of relays. First level products were available in the late sixties. Initial functions were limited to relay replacement Base PLC design has Input terminals for connection to input devices, and Output terminals for connection to output devices. Product development curve has closely paralleled the PC. Initial products were limited and expensive. As semiconductors have evolved features have increased and costs have fallen. Today's PLC are much much more than simple relay replacers being able to perform complex math, and high speed operations. Size has been significantly reduced. Today's MicroLogix costs approx.. as much as 2-3 relays Programmable logic controllers, also called programmable controllers or PLCs, are solid-state members of the computer family, using integrated circuits instead of electromechanical devices to implement control functions.They are capable of storing instructions, such as sequencing, timing, counting, arithmetic, data manipulation, and communication, to control industrial machines and processes 2

ELEMENTOS DE ENTRADA DIGITALES Pulsantes Switches Selectores Sensores de Posición Sensores de Nivel Sensores Fotoeléctricos Sensores de Proximidad Contactos Auxiliares de contactores Contactos de Relé Thumbwheel Switches 120 VAC 240 VAC 24 VAC/VDC TTL Field input devices provide an electrical signal based on a condition ON, OFF etc.. The design of the inputs determines the type of electrical signal that can be used. Different applications, and regions may use different voltages. Larger rack mount PLC’s typically support a wider range of input voltages TTL (5Vdc), 12Vdc, 24Vdc/VAC, 48Vdc, 72Vdc, 120Vac, 220Vac etc... 3

ELEMENTOS DE SALIDA Salidas Digitales: Relés 120 VAC/VDC Triacs 120 VAC Transistores 24 VDC Electro válvulas Contactores para motores Solenoides Relés de Control Alarmas Displays Field output devices are controlled by electricity being switched by the PLC. ON, OFF etc.. PLC’s “Switch” electricity, they do not “supply” electricity The design of the outputs determines the type of electrical “Load” that can be used. Different applications may require specialized output designs. Voltage/Current issues include Higher current - relays Longer life cycle - solid state (Triacs for AC, MOSFET for DC) Triacs 120Vac applications 1/2 amp maximum load MOSFET 24Vdc applications 1 amp maximum load Isolation issues can be crucial for an application. Typically the more isolation provided between output points the better. (The more individual commons the better) This provides customers greater flexibility in wiring and controlling different loads with the same PLC. 4

PRINCIPIO DE OPERACIÓN A programmable controller, consists of two basic sections: • the central processing unit • the input/output interface system The central processing unit (CPU) governs all PLC activities. The following three components form the CPU: • the processor • the memory system • the system power supply

Dentro de un PLC PROCESADOR CENTRAL MEMORIA Circuits Circuits O u t p COMUNICACIONES Circuits Circuits PROCESADOR CENTRAL O u t p Input CR Alto Voltaje Primary components of virtually all PLC’s, no matter what size are: Input Circuitry Output Circuitry Central Processor Memory Communications Port(s) Power Supply PLC’s are industrially hardened devices capable of operating in extreme environments Wide Temp extremes 0-60º C High humidity High Vibration “Dirty” Electrical Power High “Noise” (electrical) environments Alto Voltaje Aisla- miento MEMORIA Aisla- miento programa datos Bajo Voltaje AC Power Supply 85-264 VAC, 50/60Hz o DC Power Supply 5

Barrera de aislamiento Cableado de Entradas Bornera de entrada Barrera de aislamiento Elementos de Entrada 1 2 3 L1 4 P L C 5 L1 6 This is an illustration of how inputs are connected to the PLC. Power is connected to one side of the input device. The “switched” side of the input device is then wired to the PLC inputs. To complete the electrical path, L2 (electrical common) is wired to the PLC input common. This provides the electrical path for current flow, when the switch is closed (continuity) the PLC will detect the input device is on. 7 8 9 10 L2 COM 15

Barrera de Aislamiento Cableado de Salidas Barrera de Aislamiento Bornera de salida Elementos de Salida CR OUT 1 L1 OUT 1 L2 OUT 2 OUT 2 P L C L1 OUT 3 L2 OUT 3 This is an illustration of how isolated outputs are connected to the PLC. Not all Micro PLC’s have isolated outputs, isolated outputs remove any chance that an output device with unique requirements could affect any of the other output devices. Power is connected to: On isolated outputs to one side or terminal of the output terminal pair. On “common” outputs to the Common terminal associated with a specific group of outputs. The “switched” side of the output terminal is then wired to the field load. OUT 4 OUT 4 OUT 5 OUT 5 OUT 6 OUT 6 16

Los PLC vienen en una variedad de tamaños... 6

Y una variedad de formas/configuraciones PLC fijos. Modulares (con rack) Distribuidos 7

PLC Fijos Fuente de poder, Entradas, Salidas y pórtico de comunicaciones están contenidos en un solo chasis. Los elementos de Entrada y Salida están cableados individualmente al controlador fijo. Motor M1 SALIDAS O/3 OOOO PARADA I/Ø I/1 ENTRADAS ARRANQUE 8

PLCs Modulares (Lo más moderno en Flexibilidad) Componentes Mix N Match Procesadores, Fuentes de Poder y módulos de I/O enchufadas en un rack o chasis. Disponible en plataformas pequeña, mediana y grande. Flexibilidad de resultados en costos más altos cuando es comparado con el PLC Fijo. PLCs modulares son basados en rack o sin él. Allen-Bradley SLC-500 y PLC 5 son PLCs modulares OUT 0 IN 0 PROG SLC 5/03 CPU RUN FLT BATT FORCE RS232 DH485 REM DH-485 Port status indicator RS-232 Port Processor RUN indicator Processor FLT Battery status Force I/O Keyswitch RUN, REM, connection for programming terminal RS-232 Port for Power Supply Input Modules Output Modules 10

Chasis Quantum Montaje en rack de 19” opcional 4” 10” 2 Slot-4” PS CPU I/O 100mm 10” 250mm Dimensiones aproximadas 2 Slot-4” 10 Slot 17” 16 Slot 27” 3 Slot-6” 4 Slot-7” Montaje en rack de 19” opcional 6 Slot-10”

Razones para la rápida aceptación de los PLCs Situación económica Versatilidad Fácil diseño e instalación Más confiables Control soficticado Físicamente compactos Fácil detección de averías y diagnóstico

Razones para la rápida aceptación de los PLCs Se elimina el alambrado de control en beneficio de un control programable, que es el primer paso hacia un sistema de control flexible . Una vez instalado, el control puede ser manualmente o automáticamente alterado de acuerdo a los requerimientos del día a día sin cambiar el alambrado de campo. Esta fácil alteración es posible puesto que no hay conexión física entre los dispositivos de entrada y salida como sucede en un sistema alambrado. La conexión es solamente a través del programa de control, el cual puede ser fácilmente alterado.

Fácil instalación y Reducción de espacio

En grandes instalaciones las estaciones remotas I/O son ubicadas en el sitio óptimo

FACIL MANTENIMIENTO Y DETECCIÓN DE AVERÍAS

FALLAS EN UN SISTEMA BASADO EN PLCs

EL DISPOSITIVO DE PROGRAMACIÓN AYUDA A LA DETECCIÓN DE FALLAS

Preocupaciones acerca de los PLCs Especialmente por parte del personal de mantenimiento No especializado en el uso y tecnología de PLCs Caja negra El mantenimiento es dificultoso Sensitivo a condiciones industriales Programación Diagnóstico y detección de fallas Documentación

EL PROCESADOR The microprocessors used in PLCs are categorized according to their wordsize, or the number of bits that they use simultaneously to perform operations. Standard word lengths are 8, 16, and 32 bits. This word length affects the speed at which the processor performs most operations.

EL PROCESADOR The principal function of the processor is to command and govern the activities of the entire system. It performs this function by interpreting and executing a collection of system programs known as the executive. The executive, a group of supervisory programs, is permanently stored in the processor and is considered a part of the controller itself. By executing the executive, the processor can perform all of its control, processing, communication,and other housekeeping functions. The executive performs the communication between the PLC system and the user via the programming device. It also supports other peripheral communication, such as monitoring field devices; reading diagnostic data from the power supply, I/O modules, and memory; and communicating with an operator interface.

CPU CON MULTIPLES MICROPROCESADORES

CPU DIAGNOSTICS Typical diagnostics include memory OK, processor OK, battery OK, and power supply OK. Some controllers possess a set of fault relay contacts that can be used in an alarm circuit to signal a failure. The processor controls the fault relay and activates it when one or more specific fault conditions occur.

THE SYSTEM POWER SUPPLY The system power supply plays a major role in the total system operation. In fact, it can be considered the “first-line manager” of system reliability and integrity. Its responsibility is not only to provide internal DC voltages to the system components (i.e., processor, memory, and input/output interfaces), but also to monitor and regulate the supplied voltages and warn the CPU if something is wrong. Usually, PLC power supplies require input from an AC power source;however, some PLCs will accept a DC power source.

LOADING CONSIDERATIONS

MEMORY OVERVIEW The total memory system in a PLC is actually composed of two different memories: The executive memory is a collection of permanently stored programs that are considered part of the PLC itself. This area ofmemory is not accessible to the user. The application memory provides a storage area for the user-programmed instructions that form the application program. Scratch Pad Area. This is a temporary storage area used by the CPU to store a relatively small amount of data for interim calculations and control.