Controlling A Simple Automated System Using A Programmable Logic Controllers (PLC) Group

Introduction

Programmable Logic Controllers is basically used to control automated systems in industries. They are one of the most advanced and simplest forms of control systems which are now replacing hard wired logic relays at a large scale. The PLC is a microcontroller-based device with input/output circuitry that monitors the status of field connected sensor (inputs) and controls the attached (output) actuators (motor -starters, Solenoids, Speed drives, Valves etc. ) according to a user created logic program stored in the memory. In this assignment a moving conveyer with the help of motor. And A, B, C, D and E are normally open photo sensors and S is normally close photo sensor which are placed on the same horizontal level.

There are two actuators A2 and A3 that push the items and actuator A1 is used for stamping. When a block detects in sensor s conveyer start to move forward. sort the blocks into three categories. We need to sort out depending on their sizes and set apart and collected into three different groups.

Design requirements

It is required to sort the wooden blocks into following two categories at a given time. i. Blocks having a length greater than length AC ii. Blocks having a length equal or greater than length AB and less than length AC The blocks satisfying condition (i) are to be ejected by actuator A2, and those satisfying condition (ii) are to be ejected by actuator A3. The blocks satisfying neither the conditions are to be stamped by the actuator A1. The conveyor belt should be stopped at the time of stamping and there should be sufficient time for the stamping actuator to go down and come up. There may be more than one blocks on the conveyer at a given time. The sensor S detects if a block is placed on the conveyor and the belt should start moving when there is an item in the conveyor and while it is being processed. When there is no item, the conveyor should be stopped. If a second block is placed while another block is being processed, the cycle should complete when the processing of the second block is finished. When the number of blocks (which does not satisfy neither of the above conditions) exceed 3, the PLC should provide an indication (output).

Data references

A, B, C, D, E and S are sensors so there are inputs A, B, C, D and E are normally open photo sensors and S is normally close photo sensor A1, A2 and A3 are actuators so there are outputs. We need to store our information data in a bit so we choose bit memory to store data.

Analysis steps

The sensor S detects if a block is placed on the conveyor and the belt should start moving when there is an item in the conveyor and while it is being processed. When there is no item, the conveyor should be stopped. If the Blocks having a length greater than length AC. It’s ejected by actuator A2 Here I choose retentive on-delay timer because block length less than AB when detect sensor D it should stop the conveyor belt at the time of stamping and there should be sufficient time so that time If second block length greater than AC is on the conveyer that timer also pause that specific time. And that timer must be reset when the process is done. If the Blocks having a length equal or greater than length AB and less than length AC. It’s should eject by actuator A2 Same as Here I choose retentive on-delay timer because block length less than AB when detect sensor D it should stop the conveyor belt at the time of stamping and there should be sufficient time so that time If second block length greater than AB less than AC is on the conveyer that timer also pause that specific time. And that timer must be reset when the process is done. The blocks satisfying neither the conditions are to be stamped by the actuator A1. The conveyor belt should be stopped at the time of stamping and there should be sufficient time for the stamping actuator to go down and come up. When the number of blocks (which does not satisfy neither of the above conditions) exceed 3, the PLC should provide an indication (output). If a second block is placed while another block is being processed, the cycle should complete when the processing of the second block is finished.

Test Results

Explain the experimental procedure The sensor S detects if a block is placed on the conveyor and the belt should start moving when there is an item in the conveyor and while it is being processed. When there is no item, the conveyor should be stopped. When sensors A, B, C detect at the time memory M0. 1 is on and also timer1 is set when that block come in front A2. It’s ejected by actuator A2. When A, B is detecting at the same time C not detect at the time memory M0. 2 is on and also timer2 is set when that block come in front A3. It’s ejected by actuator A3. When A is detecting at the same time B and C not detect at the time memory M0. 3 is set when that block come in front sensor D. The conveyor belt should be stopped at the time of stamping and there should be sufficient time for the stamping actuator to go down and come up. If a second block is placed while another block is being processed, the cycle should complete when the processing of the second block is finished. When the number of blocks (which does not satisfy neither of the above conditions) exceed 3, the PLC should provide an indication (output).

Testing environment

1. Clean Air (Ideal condition, climate controlled or sterile)
2. Slight Contamination (Indoor, nonindustrial areas, office buildings)
3. Low Contamination (Warehouse, light industry, material handling operations)
4. Moderate Contamination (Milling operations, high humidity, steam)
5. High Contamination (Heavy particle laden air, extreme wash down environments, grain elevators)
6. Extreme/Severe Contamination (Coal bins, residue on lens)

Equipment used Retroreflective sensors: Retroreflective sensors are photoelectric sensors. They consist of an emitter and receiver in a single housing. The light produced by the emitter is reflected back to the receiver with a reflector. Whenever this light beam is obstructed, the output signal of the sensor changes state. Diffuse reflective type sensors: an object when the light beam is reflected back to the sensor. Additional features as well as different form factors will vary from series to series. single-acting cylinder: A single-acting cylinder in a reciprocating engine is a cylinder in which the working fluid acts on one side of the piston only. A single-acting cylinder relies on the load, springs, other cylinders, or the momentum of a flywheel, to push the piston back in the other direction.

Double-acting cylinder: A double-acting cylinder is a cylinder in which the working fluid acts alternately on both sides of the piston. In order to connect the piston in a double-acting cylinder to an external mechanism, such as a crank shaft, a hole must be provided in one end of the cylinder for the piston rod, and this is fitted with a gland or "stuffing box" to prevent escape of the working fluid. Double-acting cylinders are common in steam engines but unusual in other engine types. Many hydraulic and pneumatic cylinders use them where it is needed to produce a force in both directions. A double-acting hydraulic cylinder has a port at each end, supplied with hydraulic fluid for both the retraction and extension of the piston. A double-acting cylinder is used where an external force is not available to retract the piston or it can be used where high force is required in both directions of travel.

Discussion

This assignment was done for Control a simple automated system using a Programmable Logic Controllers (PLC) photoelectric sensors, single acting cylinders, siemens S7-200 PLC, conveyor belt, power supply unit, motor and connecting wires are used to implement the platform. In order to successfully detect the wooden items, we use photoelectric sensors. But we can also use capacitive sensors because wooden items can change the medium between the capacitive plates. So, the capacitance changes, can detect the items. But in dust or oil environment we couldn’t use these, because dust and oil can change the capacitance

Conclusion

The required system was simulated in a way which could satisfy all its objective but when it was practically implemented there were errors.