Industrial Electrical Control Components

No world could be described being completed thisdays without at least an application of control system. Control engineering trend is gaining more popularity in every sectors of any economy and all fields of endaveours helping us tackle the challenges of yesterday and improving the way we live and interact with our environment. Instrumentation, Automation and other areas of control engineering remains one of the bedrock of every Industrial and Domestic Processes. No single process in  industral environment would survive today tasks and process throughput without taking advantage of system automation.

Let us examine together what makes this control ability possible both for Industrial and Domestic application. In real sense, automation is getting things done quickly in a predifined way with  or without human intervention. Some Systems are classified as Semi-automatic system which are designed to function with some human intervention while some are more or less an auto pilot systems classified as Automatic systems which function with minimum human intervention. These type of systems are built with lost of control capabilities such as self diagnostic function, error and alarm reporting, event control, remote accessibility and mamy more.

In control systems, we talk majorly on two types of control systems which are Open loop and Closed loop control sytems. Open loop has control functions but does not analyse current status to anticipate changes that may affect the next actions but Close loop control systems analyse the current situation of the system being controllled and adjusted necessary parameters to correct next actions.

INPUT DEVICES

Input devices are also known as sensors. They are use to know position of  mechanism as well as used to monitor responses in various control applications. They indicate changes in mechanism positions or movements by report the changes in their initial conditions. They are sometimes being refer to as field feedback devices.

Input devices may either be digital or analogue in nature depending on designs and requirements.

Digital input devices are used to give a discrete electrical signal state in form of  ON and OFF, HIGH and LOW, 1 and 0

Analogue devices are used to determine the corresponding state of a electrical signal that is continuosly varying or changing its state, such as Temperature of a body, pressure from a pump, weight of a load, and e.t.c.

Below are some common input devices

• SENSOR OR PHOTOCELL

This are devices that indicate position or state of a moving body or mechanism by sending an OFF or ON signal accordingly. This type of signal is known as digital signal.

They are of different types in terms of designs; sensing distance, sensing media, operating voltage and fitting sizes.

In terms of design, there are inductive type, capacitive type, magnetic type, photo type and more.  This is the design method which determine the sensing media. Inductive sensor senses metallic object. Capacitive sensor senses motion, fluid, solid, distance and some of them are provided with potentiometer for sensitivity adjustment. Magnetic sensor senses metallic object . While Photo type sensor senses light reflection.

Some sensors are classified based on areas of application such as proximity sensors, level sensor, UV light sensor, motion sensor, Temperature Sensor and so o.

Two types of output refer to ON or OFF are available from output of a sensor. A POSITIVE output or a NEGATIVE output. Those that gives POSITIVE output are called PNP sensor or photocell while those that gives out NEGATIVE output are called NPN.

Two possible sensor or photocell output states are called NO (Normally Open) and NC (Normally Closed) states. The signal state is being determined by the output type. For example, NPN NO will not generate a negative output until it is being triggered. meanwhile NPN NC will generate a negative signal (HIGH State) when it has not being triggered. its state will transit from High to Low when it is being triggered. Triggered used here means when the sensor senses an object.

 Some sensor are designed to have multi-output. That is, instead of the three leads that normally comes out of a sensor, they are provided with four leads. The choice is now left to the user to determine which of the output leads will suit their application or systems they are designing. It can be NPN NO/NC (i.e. NPN with outputs NO (LOW) and NC (HIGH)) or PNP NO/NC( i.e. PNP with outputs NO(LOW) and NC (HIGH))



ENCODER
speed encoder is classified as an electrical input device used as feedback device to know the linear or rotational position of a moving mechanism such as used in servo drives, equipment cycle movement monitoring and many more.

Speed encoder has gained popularity in the control system due to the fact that it has wide area of application. I will deal with its detail in a different page on this site.


SWITCH

Switches also falls under the categories of input devices. they generally produce a digital input signals. and their contacts are either Normally Opened or Normally Closed contacts. they are in various type and sizes.

Other input devices that falls under another category classified as transducers which convert other form of energies to electrical energy such as load-cell, level sensor and many more shall be discussed on a different topic.

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