Effective use of Latch/Unlatch in an Industry to Seal in a Cylinder by Sensors Komalben PatelAnkitkumar Patel Mukundkumar Patel University of Windsor University of Windsor University of Windsor Windsor
Effective use of Latch/Unlatch in an Industry to Seal in a Cylinder by Sensors
Komalben PatelAnkitkumar Patel Mukundkumar Patel
University of Windsor University of Windsor University of Windsor
Windsor, Ontario Windsor, Ontario Windsor, Ontario
[email protected] [email protected] [email protected]– A Programmable Logic Controller is the mostly used automation tool in the world of automation control. The title represents the latching and unlatching process for sealing the cylinder by using the sensors. Capacitive sensors or ultrasonic sensors can be used to sense the input and given to the controller and according to the function of sensor, timer and counter our whole system will work. The basic process of latching and unlatching is used to seal the bottle or cylinder.
Keywords: PLC, automation, sensor, latching and unlatching
Nowadays, Automation had notable impact in a wide range of industries. Automation is helpful for reduce the human work in the production line. Automation is reducing the burden of human being as this will assist the machinery in the industries CITATION ref0 l 1033 1. So, by this way automation plays vital role in the economy market. The foremost application of automation is in the soft drink and beverages field in which exact amount of liquid must be filled unceasingly. In this application totally, integrated automation process comes in practice. Like from receiving the raw material, production process, filling, packaging and shipment of goods this all process can be done using automation. Our title is one of the part of this process named sealing the cylinder. The different process is regulated using the PLC (Programmable Logic Controller).
PROGRAMMABLE LOGIC CONTROLLER (PLC)
Programmable logic controller (PLC) is computer based, solid state and single processor devices that emulate the behavior of an electric ladder diagram capable of controlling many types of industrial equipment and entire automated systems CITATION ref1 l 1033 2. PLC is the main part of automation system in the industry. They are very efficient and reliable in all the applications like manufacturing, chemical and process industries.
Over the advance level and complex control system, the cost savings is the main advantage of the using PLC. To execute the logic of any system, PLC is widely used nowadays in control system. For implementing the logic and switching operation term ‘logic’ is being used. Switching are the input devices and motors are the output devices are connected to the PLC and then control monitor will control the input and output.
Fig.1 Parts of Programmable Controller CITATION ref1 l 1033 2In the fig typical parts of programable controller will be displayed. We can see from the figure that input signal can be sense from the sensors and it will be given to the input module. This input module gives signals to central processing unit (CPU) and CPU will decide the amount of output by using prescribed programming by programming device and according to command output signal can works. This is the process how PLC will work.
Originally PLCs were designed as a replacement for hard-wired relay and timer logic control systems. Mainly PLC having two parts: PLC hardware and programming. Now to give the programming to the PLC, Ladder logic language is used. It is also called ladder diagram or ladder logic. Ladder logic is the made of rungs and this will look like ladder. It is the standard PLC language among all the PLC languages. This language is described in standard IEC 61131-3. Ladder logic is the graphical language which uses the graphics symbol. This language is the set of lined between logical checker (contacts) and actuators (coils). If the path close or true, the rungs will give the output ‘1’ and if the path cannot find the rung will give the output ‘0’ and coil is energized and deenergized accordingly. Following are the basics command for contacts and coils.
— — Normally open contact
—— Normally closed contact
—( )— Normally inactive coil
—()— Normally active coil
By using above command motor will start run and stop. Different types of relays will be used to give the input and this relay will be sensed by the sensor.
Sensors are the eyes and ears of the control system world. If u want to control anything you must have to sense it. There are two main classification of the sensors:
Digital sensors: returns on/off signals
Analog sensor: return a range of value
Fig.2 Digital and Analog Sensor
Here is the list of most commonly used sensors in the automation industry:
Photo Electric Sensors
In our project we used two types of sensors capacitive sensor and ultrasonic sensor. The basic operation and function are explained below.
In capacitive sensor there is capacitive probe that change the electro static field in the system. When object enters the capacitive field, the electro static field will be change at that time. This change in capacitance will be responsible for trigger the sensor. Capacitive sensors are works same as the limit switches. They can be normally open or normally closed. The capacitive sensors work as a standard switch when they connected directly to the PLC CITATION Cap12 l 1033 3.
Fig.3 Capacitive sensor probe components
Capacitive sensors are most commonly used to detect the presence of either metallic or nonmetallic objects and determine the object’s position.
Fig.4 Unguarded sensing area electric field and guard field shaping the sensing area electric field CITATION Cap12 l 1033 3Capacitive sensors are more capable of detecting liquids and transparent objects that photoelectric sensors cannot. That is the main reason to choose the capacitive sensors in our system. Capacitive sensors are very sensitive to contamination and they are not dependable.
This sensor measures all the conductors like brass, aluminum, steel and even salt water.
While selecting the capacitive sensors specifications following point will be considered:
Range of measurement
Multiple channel sensing
Location of non-conductors
To increase the accuracy of the capacitive sensor following sections to be discussed:
Sensing of ultrasonic is one of the best way to sense proximity and detect level. Ultrasonic sensors can calculate distance by use of ultrasonic waves. The head of sensor emits an ultrasonic wave and receive the reflected wave back from the starting point to the achieved target. It is calculating the distance from the target by measuring the time between emission and reception.
Fig.5 Function of Ultrasonic wave CITATION Rod18 l 1033 4Ultrasonic sensors are used in grain bin sensing application, sensing of water level and drone application.
Fig.6 Working of Ultrasonic sensor
This sensor is independent from light, smoke, dust, color and material. Ultrasonic sensors are not affected by smoke or black material which makes this sensor superior than the infrared sensor. Ultrasonic sensor having higher sensing distance compare to inductive and capacitive sensor. This sensor cannot work in a vacuum and not work in underwater. Its sensing accuracy is affected by the soft material. When temperature is changed by 5-10 degree at that time the sensing accuracy is decreased of this sensor.
PLC timers are instructions that provide the same functions as on-delay and off-delay mechanical and electronic timing relays. A PLC timer provides a preset delay to the control actions.
In general, there are three types of PLC timer delays, ON-delay timer, OFF-delay timer and retentive timer on.
The terms represented in the timer block in the PLC are a Preset value which means the delay period of the timer, an Accumulated value which is the current delay of the timer.
A timer begins the counting on time-based intervals and continues until the accumulated value equals the preset value. When the accumulated value equals the preset time the output will be energized. Then the timer sets the output.
An ON delay timer is used where we need a time delay before the time delay before an instruction becomes true.
Fig.6 TON timer CITATION Aut17 l 2057 5
Fig.7 waveform of different bit of timer CITATION Aut17 l 2057 5The timer starts operating when the rung condition becomes true. The timer delay starts counting when the rung condition starts to accumulate CITATION Aut17 l 2057 5.
When the Preset value becomes equal to the accumulated value, the output is made true CITATION Aut17 l 2057 5.
The timed output becomes true sometime after the timer rung becomes true; hence, the timer is said to have an on-delay CITATION Aut17 l 2057 5.
The length of the delay can be adjusted by setting the preset value.
A TOFF timer will keep the output energized for a preset time after the rung signal has gone false
Fig.8 Toff timer CITATION Aut17 l 2057 5
Fig.9 Toff timer waveform CITATION Aut17 l 2057 5 When the rung timer is true, the output will be true without any delay. When the rung signal becomes false the timer starts operating.
The timer starts accumulating times when the rung condition becomes true, until the accumulated value becomes equal to the Preset value.
The output turns off when the output will turn false when the accumulated value equals the preset value.
A retentive timer is used when you want to retain accumulated time value through the power loss or the change in the rung state.A retentive timer accumulates time whenever the device receives power, and it maintains the current time should power be removed from the device
Fig. 10 Retentive timer
When the push bottom PB1 is pressed, the timer starts working and the reading starts accumulating.
When we push the PB1 button then rung become false and the timer stops working. Consider we are switching ON the push after a time, the timer starts counting from the previous value before the timer is stopped.
We must add another switch PB2 to reset the values in the timer
A counter is set to some preset value and, when this value of input pulses has been received, it will operate its contacts. The counter accumulated value ONLY changes at the off to on transition of the pulse input. Typically counters can count from 0 to 9999, -32,768 to +32,767 or 0 to 65535 CITATION PLC08 l 2057 6.
The normal counters are typically “software” counters – they don’t physically exist in the plc but rather they are simulated in software. A good rule of thumb is simply to always use the normal (software) counters unless the pulses you are counting will arrive faster than 2X the scan time CITATION PLC08 l 2057 6.
The CTD is an instruction that counts FALSE-to-TRUE rung transitions. Rung transitions can be caused by events occurring in the program such as parts traveling past detector or actuating a limit switch CITATION PLC08 l 2057 6.
Fig. 11 Down counter CITATION PLC08 l 2057 6UPCOUNTER
The CTU is an instruction that counts FALSE-to-TRUE rung transitions. Rung transitions can be caused by events occurring in the program (from internal logic/ by external) such as parts traveling past a detector limit switch CITATION PLC08 l 2057 6
Fig.12 Up counter CITATION PLC08 l 2057 6SEAL-IN CIRCUIT
A Seal-in circuit is a method of maintaining current flow after a momentary switch has been pressed and released. Consider a Relay is used to control the power supply to a motor. Here we are calling this relay as” Motor Starter Coil “. This Relay another NO contact is used to seal-in or latch the start signal. As start push button is a push & Release type i.e. signal will be available for some time say momentarily and then signal will be lost. so we have to latch this circuit in order to make motor run continuously even after release of start push button. For this purpose we are using Relay (M) NO contact across Start push button such that it will take care of start signal after start button is released CITATION SBh18 l 2057 7.
The seal-in auxiliary contact (NO Contact) of the starter (M) is connected in parallel with the start button to keep the starter coil (M) energized when the start button released CITATION SBh18 l 2057 7.
After Start Push button pressed : The Motor starter coil energized and its NO contact becomes NC as shown in belowfigure CITATION SBh18 l 2057 7.
Fig. 13 Seal-in circuit diagram CITATION SBh18 l 2057 7CAPPING PROCESS
In industries like bottle manufacturing industry, chemical industry and food industry some sequential processes like filling, labelling, capping and some other process take place. If these processes done by manpower then it would be slow, to make these processes fast and more accurate, industries use automation technology like PLC.
Fig.14 Sequential process diagram CITATION Moh l 2057 8PROBLEM DISCRIPTION:
Bottles are moving on conveyor belt. Screw caps are screwed to close the opening end of the bottle using rotating mechanism CITATION San18 l 2057 9.
Fig.15 Cylinder capping mechanism CITATION San18 l 2057 9CAPPING OPERATION:The bottles are transported to the capping station. IR sensors are used to sense the bottle position and according to that cylinder motor will start for 2 second and by this move bottle will reach the capping arrangement here motor will stop for 3 seconds and the capping of bottles is done using actuator arrangement. Three actuators which move in forward and reverse directions are used to cap the bottles. The actuator applies a force on the caps which are placed in their respective holders. This force helps the caps to fit into the bottles at the required position CITATION ref0 l 2057 1.
Similar to filling, if a particular bottle is not present it does not get capped. Thus, the capping is done, and the conveyor starts moving again. When the capping operation for one batch is done simultaneously the filling operation for another batch takes place. The entire sequence of operations continues until there are not bottles present in the input side. All these are automatically coordinated using the PLC. PLC gets the input from the input devices and sends the signals to the various output devices depending on the conditions that are fed into the PLC. Thus, bottles get filled and capped CITATION ref0 l 2057 1.
Basic setup for capping automation:
To sense the bottle, Ultrasonic sensor is used.
One Timer is used to stop the cylinder motor for2 second for capping the cylinder.
One more timer is used to run the motor for 1second to rotate the cylinder.
Bit Shift register is also used to perform this operation.
Tally the number of steps capping machine is placed from the sensor and set bit position to operate capping machine accordingly. As you can see, bottle is away from the proximity switch, so if Bit register B3:0 is used, then capping machine should be operated when B3:0/0 is shifted to B3:0/6.Two inputs are given to this Capping machine, electric supply to run motor and pneumatic supply to push machine down cap ram CITATION ref0 l 2057 1.
Fig.16 Ladder logic diagram CITATION San18 l 2057 9RUNG001, RUNG002 and RUNG003 are used to operate cylinder motor.
Assuming it takes 1.6secs to screw cap a bottle, conveyor is stopped for 2secs and capping is done.
When the system is started, cylinder driving motor with address O:2/1 runs for one 1sec and stops for 2secs. Timer is set to auto reset mode by giving XIO of T4:1/DN in series to it. T4:0 is used to de-energize cylinder driving motor coil with address O:2/1 after 1sec and T4:1 is used to energize the same coil after 2secs CITATION San18 l 2057 9.
RUNG004, RUNG005 and RUNG006 are used to operate bit shift register BSL and Capping Machine with address O: 2/2.Whenever Ultrasonic sensor with input I:1/2 detects bottle and O:2/1 is energized, I:1/2 sets B3:0/0 bit. This bit is shifted when again this coil is energized. From proximity to capping machine, distance is 7 steps. Hence bit B3:0/6 of B3:0 register is used to operate capping machine. Capping machine motor relates to output O:2/2 which is energized till the process is running. Hence, simply letting master coil run the capping machine motor .When Accumulator value is between 2 to 18, pneumatic supply is activated, and screw capping is operated that is when cylinder motor is stopped for 2secs and timer is between 0.3-1.9secs CITATION San18 l 2057 9.
This project is created on the application of industrial automation. With PLC, industries are not as much of dependent on manpower. This system meets the demands of today’s marketplace which need high production with high quality. The system delivers accuracy and efficiency using the materials with low consumption. Additional benefit is the language used for the programming of the PLC is very useful to run all types of engineering application since ladder logic is the most commonly used language method. The power used up by the PLC is also small CITATION Pro15 l 2057 10.
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