Liquid Level Controller System: Design And Implementation

This assessment requires you critically analyse the system design process of a project using the theory and principles studied during the course. This assessment item relates to the course learning outcomes 1 to 5.

Your group has already analysed the conceptual design of a project in Assignment 1. In this assignment, you are required to write a report which critically analyses the preliminary design and detailed design phases of the project discussed in Assignment 1. Particular attention is to be paid to the system test, evaluation and validation processes employed and any optimisation that was required. In the Introduction, you will need to briefly summarise the content covered in Assignment 1.
To demonstrate your research skills and understanding, the report must draw upon relevant sources like journals, books or reputable trade publications in analysing the project. You must also present the case study in terms of the above two lifecycle phases and evaluate the detailed design against the identified needs / requirements. 

The Importance of Liquid Level Control

Nowadays, a very significant problem is the controlling the resources of water around the whole biosphere. Water is normally needed for many uses in agriculture, homes and industries.  There are many types of the liquid level controller but the major ones are those overflow control used to stop overfilling the highest level that a storage tank can hold. Other types of the liquid level controller systems are the ones with completely draining to prevent the pumps from working without the liquid. There are some cases that both methods are connected for the extreme use of the pumps and to reduce the time work frequency. In many processes of the industries, control of liquid level is very important matter. It was recorded that estimates of 25% of the emergency closures in the nuclear power plant are triggered by the bad control of the steam generator water level. Such shutdowns reduce the accessibility of liquid level controller plant and a need of the enhancing effective performance in the present level controller is therefore required.

The controller system for the liquid is very important to stop the losses that might happen because of the overloading of the liquid in the tank that depends on the liquid type being pumped into the tank. Overfilling of the tank may result in the overflow of the liquid that can be hazardous if the liquid is destructive to the health of human or flammable. The time wastages, dangers and the effects of health caused by the overloading of the liquid that is pumped by the electric pump is the main purpose why the proposal of the liquid control system is important for both commercial and households' drives. This paper pursues to come up with the preliminary and the detailed plan of the liquid controller system that can be useful both for the commercial and small-scale purposes.

This part introduces the preliminary design of the water level controller which is the simple, cost-effective and efficient design of an automatic liquid level control system. It can be used effectively either in the oil, the house held water tanks, or the liquid tanks in the industrial sector. The main function of this system is to automate the off and on control process of the flow pumps to control the refiling process for the tanks with liquids. This system design is built on the idea of the using single inverted set input flip-flop to do the needed level control tasks with an aid of the suitable element of driving and two simple level of discrete sensors to sense and detect the liquid level in the tanks (Altmann, 2010).

Preliminary Design of Automatic Liquid Level Control System

There is much design of the automatic control system created on the groups of dissimilar control techniques. Most of the proposed designs are based on the microcontroller and the use of microcontroller to automate the procedure of water pumping in the overhead, and underground tanks storage systems and has the capability to notice the level of water in the tank by switch off and on the pump and show the status on the screen of LCD.  The microcontrollers can also be used in the management of the process using the wireless level sensors instead of the wired sensors. Also, there are other devices of control and techniques based on the design of the control system. The innovative designs of the liquid control system that can treat and enhance all the consideration in the design suggested as complexity, reliability, cost-effectiveness, consumption of power represented.

The system is comprised of 4 major units; power unit, driving unit, sensor units and control unit (Bequette, 2016).

Power unit; this unit supply the needed power to the sensor and the control units, it gives around zero to 5DC voltages which are needed for the operation of the corresponding digital ICs and the sensor levels (Bhattacharya, 2013).

sensor unit; the sensors sense the level of the liquid in the tank, it has two level sensors that are discrete, the first sensor is located at the bottom of the tank to sense when the tank is empty and the second sensor is located on tanks’ top to sense when the tank goes full of the liquid. The sensors can be designed to work as follows; give the output at logic 0 level that ranges from 0 to 2 DC volts when there is no water on the level determined to sense, it also gives the output at the logic 1 level that ranges from 2.5 to 5 DC volts when the liquid is at the needed level to sense. The sensor outputs will represent the input for the unit control which executes the needed control task that depends on the values of the sensor outputs (Corripio, 2016).

Control unit; the control unit is the sign in the system to implement the effective control until it should be known how the system work which can be described below. If the tank is empty, the output sensors will be very low at zero so the pump should be turned on so that the tank can be filled. When the pump starts filing, the liquid flow to the tank and the sensor status at the bottom changes to high around 1 and the pump should continue filling. When the tank is full, the pump turns off and the level of the liquid start to reduce and the sensor status at the top changes back to low. The pump should be turned off unless the tank is empty again. The operation process will be repeated (Ibrahim, 2015).

Types of Control Systems

Driving unit: this unit is responsible for the driving pump flow that depends on the change in the flip-flop status logic. In this type of preliminary design, the simple relay devices are used to drive the flow pumps' operation.

The process requirement in many industries, firms and homes includes the overhead tanks for the water which is frequently fed through the electric pump which is turned off when the tank is full and on when it is unfilled. The best collective way of knowing when the tank is filled is through detecting when it run-offs the brim. These losses can be stopped if the tank is controlled automatically by inserting the mechanism of the feedback control capable of tripping the pump off or on as needed. Even though the pumps equipped with the motors of variable speeds can be effective for the mechanism of off and on. The commercial sensors that are available are expensive and cannot be used in all the households (Kumar, 2013).

The control systems are grouped as the closed and open loop, in the open loop system the command is sent to the system and it assumed the system perform appropriately. The closed-loop system compares the output and results of the system to the required output, takes effective measures and it exhibits the accurate performances. Also, it tends to be unstable and more costs. One of the most used manufacturing tanks is the coupling system. A couple tank system is comprised of the liquid tank, where one of the tanks is used to take the incoming water and keeping the distinction of the liquid as the preferred need. The second tank is normally used as an output to supply the liquid at the stable temperature (Mohd, 2017).

Some of the writings have been done by the use if the sensor that measures the level such as the ultrasonic and capacitive sensors. The microcontroller is used as the processor of the data and controller of other circuits like sensor level as the GMS modern. This system reports the measurement end result through the spot SMS which means that the user doesn't need to come to the site to measure directly. The digital microcontroller for the level of liquid based on two transducer optical fibres. New magnetostrictive sensor, liquid level online and the equipment that measures the density should be developed. With the algorithms correction, the resolution measuring of the magnetostrictive meter liquid may reach 0.1mm and the magnetostrictive dosimeters reach the 0.0001grams per centimetres cube (Mutambara, 2015).

Sensor Unit

This system uses the ATMEGA 32 microcontroller kit board as the key controller. Uninterrupted fluid level sensors, level presentation, and the circuit that monitor the pumping. This system design is to measure the liquid level and regulate the position of the pumping unit for monitoring. The ATMEGA 32 microcontroller kit started board as the system essential is little voltage and great performance microcontroller and the major used to control the position of the states of unit pumping permitting to the level of the liquid.

The e-tape sensor is in the state of solid, multilevel, sensor that sense the fluid level for measuring the water level, water-based that are not corrosive and dry fluid such as powders. The e-tape sensors are made using the technologies of the printed electronics which employs additive straight printing procedures to give out practical circuits. The e-tape sensors are compacted by the fluids’ hydrostatic gravity and it immersed the results in the alteration in resistance that resembles the distance from the sensor top to the fluid surface. The e-tape sensor gives the resistance output that is proportion contrariwise to the liquid level and the lower the level of the liquid the greater the resistance output and the upper the level of the liquid the lower the resistance output (Parr, 2014).

To regulate the level, the sensor is placed in the tank, the connection of the pin of the e -tape sensor is done and the voltage of minimum and maximum level of water in the tank. The output divider is connected to the ADC microcontroller. This is the significant portion which is to regulate the unit of motor that pump. The control signal from the board is sent to the circuit of motor pumping when the liquid level at certain levels or prevent the motor when under the value to stop the idling liquid.

Temperature circuit uses to measure the temperature conditions in the tank. Solitary line digital sensor for temperature can be used. A seven display section or the indicator is a type of the device that shows electronics by displaying the decimals numerals that is a substitute to more complex display. Total software written by the C language included in the sole techniques, where based on this strategy the coding is written in a different file. There are many files that can be made in this projects and named according to their functions. Every file comprises two kinds that are referred to the program and the header file. Showing level of liquid and the unit of the motor that controls the pumping is lamented in major routine, which is the system core of the software and disrupts the assist subroutines called in it (Passino, 2010).

Control Unit

  In order to do the testing of the system established, it was joined to the 0.37KW Ac water pump even though any other pump of AC can be used. The AC water pump can be used to resource water to the overhead tank. The highest level was set at the 50^th litres and the lowest was set at the 10^th litres. The pump was connected through the control devices knows as the regulators but the sensors were dipped in the tank and joined to the regulator by the insulated output cables. The pump was turned on and set to resource the water to the tank. When the water reached high the regulator switched the pump off. To test the low-level sensor water was removed from the tank continuously till little level was achieved at where the point the regulator turned on the pump automatically. Hence the regulator maintained the level of water successfully amid these limits as long as there was the supply of the power to the system (Shunta, 2012).

These phases analyses the optimization, evaluation and validation of the liquid level controller system

The firmware in the microcontroller gives the data reading capabilities to the software via the USB. The GUI software manages the functions such as the initializing the ADC, processing the ADC data output after collection, and calculating the codes for the volume to be dispensed.  During the initialization of ADC went through the process of self-calibration that allows the buffer of the input signal and disables the gain calibration of the system and offset calibration of the system. Selection of the rate of sampling is very significant in the liquid measurements in industrial application. The ADS allows the acquisition of fast data with good power line rejection. The proposed outside clock for the frequency of the line rejection which is efficient for the data rates. For 50Hz frequency line rejection, the proposed external clock is around 2.1 MHz that is efficient for the rates of data. This improves the measurement precision since it removes the effects of shunting of the input current dynamics (Syauqi, 2014).

This goals of the optimization are to maximizes the efficiency and reduce the costs. This system can be optimized by the introduction of the complex parts that can be fixed to make it better. The modern sensors can be used and also different microcontrollers can be put into practice for optimization. The mat lab software can be used for simulation so that the systems validation can be approved in another way. Changes can be made to the preliminary and the detailed design of this system for the between performance both in present and future generation

Driving Unit

This system measures the volume by measuring the liquid height influenced by the pressure in the closed tube with the liquid pushing the air inside. The pressure will be proportional directly to the liquid height in the container. The trapped air in the inner tube makes the pressure to build there. The higher the rises of the liquid the more pressure built. The system gives the good reading if the height of the liquid in the large vessel. With the out vessel fixed diameter, the total volume can be evaluated by using a simple calculation (Mutambara, 2015).

For the hydrostatic pressure generated by the column of water at the bottom of the controlled reservoirs of the liquid uses the air trapped in the measuring tape to generate the similar amount of the pressure on the sensor. At its output, the pressure sensor produces a pressure similar voltages measures by the digitalized DC processed by the microcontroller and sent to the PC via the USB cable. The PC and GUI send the requested delivery to the DAS that activates the PCB valve driver to deliver some liquid amount defined by the software. The DAS also gives control signals to the PCB pump driver to turn off and on so as to maintain the constant liquid (Zhang, 2014).

Figure 4: Evaluation process for the controller system (Ibrahim, 2015).

Conclusion

This paper presented the detailed and preliminary design of the liquid level controller system. Is has covered various subtopics on how the system can be evaluated, validated, optimized and also tested. In practice, there are numerous categories of liquid level control systems that can be done but the major ones are those surplus control used to stop surpassing the highest level that a storing tank can hold and those with completely drain to prevent the pumps to work without the water. There are some cases that both methods are joined for the extreme use of the capacity of pumps for decreasing the frequency starts and to decrease working for a little duration. In many processes of the industries, control of liquid level is very important matter. It was recorded that estimates of 25% of the emergency closures in the nuclear power plant are triggered by the bad control of the steam generator water level. The time wastages, dangers and the effects of health caused by the overloading of the liquid that is pumped by the electric pump is the main purpose why the design of the liquid level control system is important for commercial and households' drives

Altmann, W., 2010. Practical Process Control for Engineers and Technicians. Paris: Elsevier.

Bequette, W., 2016. Process Control. Michigan: Prentice Hall Professional.

Bhattacharya, S., 2013. Control of Machines. Toledo: New Age International.

Corripio, A., 2016. Design and Application of Process Control Systems. Carlifonia: ISA.

Ibrahim, D., 2015. Microcontroller Based Applied Digital Control. Chicago: Wiley.

Kumar, A., 2013. Concepts of Biophysics. New York: APH Publishing.

Mohd, S., 2017. Fuzzy Logic Controller Simulation for Water Tank Level Control. Michigan: KUKTEM.

Mutambara, A. G., 2015. Design and Analysis of Control Systems. Perth: CRC Press.

Ogata, K., 2017. Modern Control Engineering. Perth: Prentice Hall.

Parr, E., 2014. Programmable Controllers. Colorado: Newnes.

Passino, K., 2010. Biomimicry for Optimization, Control, and Automation. Michigan: Springer Science & Business Media.

Shinners, S., 2017. Modern Control System Theory and Design. Chicago: John Wiley & Sons.

Shunta, B., 2012. Design of Distillation Column Control Systems. Colorado: Butterworth Heinemann.

Stewart, M., 2016. Gas-Liquid And Liquid-Liquid Separators. Toledo: Gulf Professional Publishing.

Syauqi, A., 2014. Level Control (tank 1) of Coupled Tank Liquid Level System Using Integral Control State Feedback Controller. Paris: UMP.

Zhang, W., 2014. Software Engineering and Knowledge Engineering. Melbourne: Springer Science & Business Media.