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EE/CE 201 Project Report Fall 2021

Title of the project

Section number

Student names and IDs

Abstract There have been increased trends in digital weighing machines in the modern world instead of the analog systems used before. 1The design of an automated weighing system conveniently measures the weight of a material object and come up with accurate results. This project covers the design of an automated weighing system. The weighing system measures objects' sizes, colours, and weights. Test results were determined by placing an object into a container and the system left to measure its weight and determine whether it is in an acceptable weight. When the weight is within the desired range, a green light will be turned on, whereas if the weight of the product measured is not desired, a red light is indicated on an LCD screen, and it will flash the object. In the project, an extension spring in the analog weighing scale is converted into voltage using a voltage divider circuit. Design an Automated Weighting System Objectives, Criteria and Constraints Objectives The project covers the design and implementation of an automated weighting system for accurate measurements of different weights. The automated weighting scale will use more precise digital sensors to detect the weight passing over through the system. Weighing scales in most companies apply force sensors in measurements of various loads passed through them. 3Some of the most implemented designs in weighing scales are using resistive load cells configured in Wheatstone bridges. The interfaces used for the sensors are often complex due to precision requirements. The signal levels are low in load cells and the effects of noise cause distortion. The project aims at measuring the signals correctly to ensure the requirements of precision are met to ensure high accuracy measurements of objects measured. The automatic weighing system will make highly accurate measurements by using a clear interface boosting circuitry, which will deal with precision issues and battery conditions. The system will determine whether it is of acceptable weight or not by use of sensors and display a green light if acceptable and red light if not acceptable. Criteria and Constraints. To ensure successful design, the criteria and constraints involved in the design include; Correct Measurements- The design involves high precision results to detect the drifts on load measurement parameters. The measurements are taken of the products to be accurately measured to give the required output in the display. Over exceeding or under measurements value indicated in the diode means different colors. Time-the design process will require timely carrying out measurements in the project to complete every cycle of the objects placed in the weighting scale. Time will be key for each action process to ensure accurate measures are taken. Environment- The environment is another important criterion for achieving the desired results of the design. Having the appropriate design environment will lead to precise results, ensuring the right achievement of results. 5Some of the factors influenced by the environment include; vibrations which may lead to incorrect interpretation of results, shock loading involving placing heavy materials on the weighting systems damaging the load cells, wind loading affected by sudden air movements, and unclean scales leading to inaccurate results being obtained. Safety- Safety is another concern that is essential in the design process. The area will need to remain need and tidy to ensure the smooth completion of the project. Sensitivity-sensitivity is a constraint in the weighing scale design, and it has been one of the important aspects of the weighing scale. The sensitivity of the weighing scale will determine the accuracy of the results to be obtained. Nonlinearity-This is another constraint that was considered in the design of the weighing scale. Most mechanical balances do have their non-linearity, which arises due to their construction. Creep recovery- the change in weight measurements over time being weighted also acts as a constraint in the design process. The effect is majorly based on the material's ability to be elastic. The public health-public health concern is another key factor to consider in the weighing scale design. A good design process involves the ability to follow health important aspects such as standard operating procedures of safety to ensure correct results are obtained at the end of the design process. Theory The automatic weighing scale is a digital weighing scale that is considered one of the most accurate devices used in most industrial applications to measure objects' weights. An automatic weighing control system is used in industrial fields for exact measurements of manufactured objects. This development has become an essential task due to the declining availability of labour and the high demand for products. In addition, automated weighing systems are developed from mechanical standing alone electronic devices that use a PC or a microcontroller. 6The software-based ones can effectively communicate through the digital interface through peripheral devices. The progressive industrialization in the 19th century ensured a high working speed which was easily solved by the automated weighing systems used in cases of bulk entities such as grains and raw materials loaded into them. There has been a continuous increase in demand for automated weighting systems today as they are user friendly and can be applied in many applications. This trend has been adopted in most parts of the world as it turns out to be much user friendly in most practical applications where it is used. The design will involve modifying and restoring the manual weighing system with an automatic one for accurate and precise measurements of products. Various types of machines are used in the weighting industry but are deemed unsuitable in industrial applications. The industry needs automated control to accept or reject products according to their particular weights. The products will be checked, passed through the automatic weighted control and then forwarded to the next step for packaging. The rejected product will then be returned to the assembly stage. The automatic weighing scale uses force sensors in measuring the load placed on top of it. The implementation of the automatic weighing scale design involves using a resistive load cell that is aligned in a Wheatstone bridge. The interfaces of the sensors are usually complex, which is a tool to bring out more precise measurements. Weighting scale systems usually require an analog front end in making many accurate measures and clearer interfaces and boost circuits in dealing with battery conditions. The construction of the automated weighting system will make it easier for people in the industrial sector to carry out their duties effectively. The sensor will detect the accurate measurements, and those below the required threshold are rejected with an indication of red light and need to add the products until the desired level is attained.

Procedure

Design Process The design process will involve both the mechanical and the electrical parts in the system. The mechanical part will include modifying the system enabling conversion of mechanical compression of the spring to corresponding electrical quantity, whereas the electrical system involves digitalizing the analog voltages. The project's testing will follow placing the products in the automated control system. The weight of the object found, if the object's weight is desirable, gets to be accepted and rejected if not accurate. The comparator measures the measured weight in the design, then sent to a signal inversion unit and transmitted to a Relay Driver driving the motor enabling the product to be accepted. The output of the comparator is set to the signal amplifier, which amplifies the signal and then takes it to the Relay Driver. The block diagram showing the process of the automatic control system is as below;

Fig 1. Block Diagram: Automatic weighing system

Hardware Components

Rheostat This component is a summing means in which the pressure, which results from the weight object, is transformed into the rheostat resistance change. The varying resistance makes a voltage drop, and the ultimate voltage becomes available in the output pin. The pins are three where pin 1 acts as an input, where 5volts is applied. The ground is pin two common for both the output and the input. The output is obtained in pin 3.

Fig 2. Rheostat

Conveyor Belt. It is used in conjunction with the pallet computer allowing for much effective manufacture and retail distribution. They are usually used as they save greatly in workforce and transfers volume in different locations to allow companies receive and ship bulks with small expenses in labour. A direct current motor is one in the output, and it gets driven by the instructions provided by the operator. The motor gets to be driven by 12 volts, 5 amperes current supply. The surveyor belt is fitted with a metallic stand having bearings.

Fig 3. Conveyor Belt.

Relay Cards This instrument comprises various relays mounted in a Printed Circuit Board (PCB). The relay acts as a switch utilizing the armature, and an electromagnet in completing the circuitry powers it. They are usually used to operate circuits that provide power to motors. The relay comprises four components comprising of the electromagnet, spring, and set of electrical contacts attached to the armature. When there is no power operating the electromagnet, the armature gets held in position by a spring keeping it from making contact with the electrical circuit it is stated to operate with.

Fig 4. Relay

NOT gate The NOT gate is also known as Inverting Buffer with an output level at logic level '1', inverts its input signal. The output coming from the device is usually at logic 0, and it is deemed to be “LOW” and “HIGH" when it returns to logic level 1.

Fig 5. NOT gate

Relay Driver IC (MAX4896) The relay driver is designed for use at voltage application of 50 volts. The instrument comprises 20 of 4mm by 5mm. The device helps in protection against overcurrent and gives inductive inducement protection.

Fig 6. MAX4896 relay driver

Power supply unit This is a mandatory element required to run the whole circuit. The power supply is rated well to ensure that the circuit works well. A 5 volts supply was chosen for the transducer to reduce the complexity of the whole system. A battery was chosen in this case as it is portable.

Fig 7. Power Supply unit

The LCD The LCD was used to display the weights of the products that were to be measured. The unit display included 16 characters with the ground terminal connected to the 5 volts terminal. The 8-bit output of the Analog-digital converter was connected to the LCD.

Fig 8. LCD

Diodes Two diodes were used in the system design to indicate whether the objects that were being measured reached the required level measurement. A red diode indicated that the measured weight was less than required, while the green diode showed the object met the recommended threshold.

Fig 9. Diode

The complete circuit for the design of the automatic weighing system is as below;

Fig. 10 Automatic Weighting System

Complete Results and discussion When the weighing control system gets switched on, the object to be measured through the use of the sensor records the weight. The weight measured by using a comparator compares the weight if it reaches the required amount. The LCDs the recorded weight. If the recorded weight is below 500g, the red diode lights up and rejects the object. In that case, the output for the comparator is given to the signal amplifier, which tasks to amplify the signal to the relay driving the motor making the product rejected. If the object measured reaches 500 g, the diode displaying the green light indicates that the object is allowed to pass and gets to the packaging unit. The NOT output facilitates the signal conversion, which is then given to the relay driver and gets the product to be accepted. The weighting system is designed to follow these steps as in the flow chart below;

Fig 10: Automatic Weighting System flow chart.

The weighting system thus accurately measures the product weight in the industry, rejecting the inaccurate weights of the products automatically. The system is important in packaging the products and proper packing of different products while rejecting the inaccurate ones. Every component used in the design process was tested to ensure that it worked efficiently. The circuit was tested and then soldered permanently in a Vero board. Risk analysis involved carrying out various tests on the system this included; Range test- The range test was carried out to determine the values of which the scale was to be used. The reading was taken where there was no load in the system. This was for the lower limit, while the higher limit was taken for the high limit when the test object was placed on top of the system and then ran for some time. Accuracy test- This test was conducted to determine how accurate the tested results were. A standard weighting machine was introduced where the results being tested in the system were then correspondingly compared to check if there were disparities and then corrected. Conclusion and future work The automatic weighing system was designed for accurate and precise measurements of products as they passed through the system. The undesirable weights were allowed to pass with an indication of green light. In contrast, the undesirable ones were rejected by using a comparator, which helped display values in the LCD screen and the indication of red light on the diode. This helped ensure the work was carried out in a faster manner and ensured the operator's workload was made easy in the identification of the weights which had not reached the required threshold. The system developed was able to read the results digitally, making work easier. In this design, the system could be a game-changer in the industrial sector due to its ability to detect and differentiate various weights passed through the system accurately. Another advantage is that the system is much more linear and compact and could also be useful in other sectors such as homes and offices inaccurately and precise measurements carried out on weight measurements. However, the correct loading and placement of loads in the weighting system need to be done carefully in a recommended range to avoid deformations. The future looks into coming up with a more improved system that will ensure it is much accurate and precise than the present design to reject the constraints and disparities and come up with a universal fit that would measure all types of loads, including machines such as excavators and backhoes.

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