Scenario: You are a floor engineer in a manufacturing plant. You suggest that th

Question

Scenario: You are a floor engineer in a manufacturing plant. You suggest that the plant needs modernization, in order to keep the plant running efficiently. You are required to educate your superiors on moving towards using PLC controlled machines, and retrofitting some relay controlled machines to PLC Your proposal for the PLC controlled Bottling Plant Keeps the existing conveyor, filling and bottle capping system, but will incorporate quality control systems to ensure bottles are properly capped, and keep track of quantities produced, all data is to be relayed via network to the sales department Figure 1: Bottle filling operation Presentation to technical and non-technical staff is required from you on selected subject matters

Explanation / Answer

Sensors which generate analoge signnal such as pressure sensor, temperature sensor, speed sensor, analoge signal should be used ideally. But the problem with the analoge signal is that they can't be processed on a digital processor directly, Analoge to digital converter (ADC) is used. Another problem associated with the analog signal is that they are vulnerable to noise as compared to digital signals. So if possible digital signal is preferred in most of the cases.

1.

Actuators like stepper motor take digital signal as their input digital signal is required to interface them with the PLC

2. Speed sensor generates analog signal so analog signal should be used to interface them with the PLC. But a ADC can be connected to the speed sensor if we desire to use digital signal.

3. Pressure switch generates digital signal (1 or 0) when the pressure at the input is above or bellow a certain threshold. So digital signal should be used to interface pressure switch with the PLC.

4.LDR stands for light dependent resistor.It's resistance varies proportionally with the light falling on the sensor in a alnalog manner. Generally it is used with an Op-Amp as a proximity sensor which senses presence or absense of a bottle.(0 or 1). So digital signal should be used to interface it with the PLC

5.Almit switch ?is an electromechanical device that consists of an actuator mechanically linked to a set of contacts. When an object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection. to digital signal should be used in this case as the signal generated from the sensor is descrete.

Optical shaft encoder

Opticla shaft encdoder is used to measure the angular position of a disc.he optical encoder's disc is made of glass or plastic with transparent and opaque areas. A light source and photo detector array reads the optical pattern that results from the disc's position at any one time. The optical pattern is descrete in nature, so the opticla shaft encoder's output is digital in nature.

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