http://dspace.ewubd.edu:8080/handle/123456789/172 2026-04-05T23:50:15Z http://dspace.ewubd.edu:8080/handle/123456789/1045 PLC Controlled Automatic Bottle Filling System Hasan, Md. Mahadi; Fuaduzzaman; Moinuddin, S. M. Programmable logic controllers (PLC) are used in places where automatic control of the machineries is required. They are especially useful in industries to run various tasks without human intervention, so, PLCs are now used in many industries where process automation is required. They are built to withstand the harsh environment of the factory floors and have greater immunity to noise and vibrations. However, to use a PLC to control a process, it needs to be programmed according to the requirement of the process to be controlled. In many industries (such as pharmaceuticals, beverage industries etc.), bottles are required to be filled-up with a per-determined amount of liquid. The filling process is usually kept automated to ensure a higher production rate and to lessen the burden on human resources, since the human operator is required to take only a supervisory role here. The whole process of bottle filling is therefore performed automatically through machines which are controlled by PLCs. In our project, we have built a PLC controlled automatic bottle filling system. We made a mechanical model of the industrial filling system, complete with sensors, motors, actuators etc. and controlled the whole process of bottle-filling using the PLC available in the EEE laboratory. The system consists of an assembly line, and when a bottle reaches the filling station, a fixed amount of liquid is filled into the bottle, and then it moves towards the end of the assembly line to make way for another bottle to be filled-up. Although this type of PLC controlled systems already exist in the industries, but through designing and implementing the system ourselves, we obtained experience on how to design practical industrial systems and control those using PLCs. This thesis submitted in partial fulfillment of the requirements for the degree of B.Sc in Electrical and Electronic Engineering of East West University, Dhaka, Bangladesh 0008-01-01T00:00:00Z http://dspace.ewubd.edu:8080/handle/123456789/1044 Decisive Factors and Impacts of False Detection in Spectrum Sensing in Cognitive Radio Lailun Nahar; Ruthi, Sameha Zaman The increasing demand for wireless communication introduces efficient spectrum utilization challenges. Cognitive radio has emerged as the key technology to address this challenge which enables opportunistic access to the spectrum. The main potential advantages introduced by cognitive radio are improving spectrum utilization and increasing communication quality. Cooperative spectrum sensing improves the probability of detection by collaborating to detect primary user's signal in cognitive radio (CR) system as well. The goal of this thesis is to cooperate the cognitive users to increase the detection probability for a given probability of false alarm and find out the better condition of sensing spectrum among three rules: AND, Majority, OR. Here, we propose a cooperative spectrum sensing and signal detection in the CR system by implementing AND rule, Majority rule and OR rule under the AWGN channel and fading channel. To find out better detection, here we compare between AND, Majority, and OR rules. It is observed that the probability of detection for a given value of probability for the false alarm has been significantly achieved by optimal value of detection probability in AND rule, Majority rule, OR rules as the number of the user increases. Finally we also see the effects of fading over the spectrum sensing. We have observed that due to fading condition, the amplitude of signal deviates. In fading condition AND rule gives better performance in detection probability among three rules. This thesis submitted in partial fulfillment of the requirements for the degree of B.Sc in Electrical and Electronic Engineering of East West University, Dhaka, Bangladesh. 0008-01-01T00:00:00Z http://dspace.ewubd.edu:8080/handle/123456789/1042 The Effect of Bias Polarity Dependence on the DC Electrical Characteristics and Sensitivity of Silicon Nanowires for Biosensing Application Pinkey, Rifat Nigar; Tasnim, Shams Zinat We investigate the effect of bias polarity on the DC electrical characteristics of p-type silicon nanowires and its effect on the gate sensitivity for possible application as biosensors. A 75 nm thick nanowire with doping concentration of 1014 cm-3 is investigated for different channel lengths. It is found that when drain and gate voltage both are positive nanowires ID-VD characteristics typically exhibit non-linear diode like characteristics with no appreciable conduction up to a certain level of drain bias. The gate sensitivity of nanowires at this mode of conduction is estimated and found to be 18.9%/V for a channel length of 1 μm which reduces to a value of 12.5%/V for the channel length of 100 nm. When gate voltage is positive and drain voltage is negative no appreciable conduction is observed and the gate effect is diminished at short channel lengths which implies that at this mode of conduction p-type Si NW might not be suitable for biosensors. When gate voltage is negative and drain voltage is positive nanowires exhibit less non-linearity and with the increase of negative gate voltages perfectly linear characteristics is achieved through the accumulation of holes in the nanowire by the gate effect. The sensitivity of nanowires at this mode of operation is found to be 11.318%/V and 7.549%/V respectively for 1 μm and 100nm channel length for a gate voltage change from -2v to -1.5V with a drain bias set to 8V. These levels of sensitivity agree very well with the reported sensitivity of silicon nanowire biosensors. However, when both gate and drain voltages are negative a drastic change of the nanowire characteristics is observed and the 75nm thick nanowires NWs are behaving perfectly as a transistor. It is observed that in this mode of operation sensitivity is very high compare to the other modes of operation for all channel lengths. For 1μm channel length, sensitivities obtained are 199.866%/V (when VG =1-1.5), 154.373%/V (when VG =1.5-2) and 103.604%/V (when VG =2.5-2). For 100nm channel length, sensitivities obtained are 35.019%/V (when VG =1-1.5), 42.058%/V (when VG =1.5-2) and 38.333%/V (when VG =2.5-2). This result indicates that for p-type Si NW application of negative voltages to both VG and VD are the most viable mode for biosensor operation. We also investigated sub threshold characteristics of nanowires and it is observed that nanowires can be set to exhibit excellent sensitivity with an appropriate VG range if it can be ensured that NWs fall within the subthreshold region of operation. Sensitivity values of 285.713%/V and 174.187%/V are achieved respectively for 1 μm and 100 nm channel lengths with positive drain voltage and negative gate voltages and sensitivity values of 307.6 %/V and 285.7 %/V are achieved respectively for 1 μm and 100 nm channel lengths with negative voltages both at drain and gate by ensuring sub-threshold regime of operation. This investigation reveals the requirement of appropriate biasing scheme for highly sensitive bio sensor operation and is very significant for nano wire based bio sensor applications as transistor behavior can be set by choosing appropriate bias conditions which would allow large conductance charge upon attachment of Bio molecules and a highly sensitive biosensor could be realized. This thesis submitted in partial fulfillment of the requirements for the degree of B.Sc in Electrical and Electronic Engineering of East West University, Dhaka, Bangladesh. 0008-01-01T00:00:00Z http://dspace.ewubd.edu:8080/handle/123456789/1041 Effect of Lightly Doped Drain on the Electrical Characteristics of CMOS Compatible Vertical MOSFETs Hossain, Md. Delowar CMOS compatible ion implanted vertical MOSFET has been recently demonstrated as a viable route for improving RF performance of matured CMOS technology. Unlike planar MOSFETs, in this type of devices heavily doped and lightly doped drain is provided by single implantation and anneal. For this reason depending on anneal time the depth of LDD and doping is determined which could have unavoidable effects on vertical MOSFET’s electrical characteristics. In this thesis I investigate effect of LDD doping on the CMOS compatible vertical MOSFETs structure. Electrical characteristics of 100nm vertical MOSFET is investigated for different values of LDD and body doping values. It is found that with the increase of LDD doping drive current of vertical MOSFET increases whereas subthreshold performance is degraded. The degradation of sub-threshold performance is found to be more prominent at low body doping values. In addition to this threshold voltage of vertical MOSFETs are found to decrease with the increase of LDD doping. These effects are explained by the reduction of the effective channel lengths and decrease in the source/ drain series resistances with the increase of LDD doping values. These results are very significant for choosing appropriate body doping and LDD doping values for fabricating 100nm CMOS compatible vertical MOSFETs. This thesis submitted in partial fulfillment of the requirements for the degree of B.Sc in Electrical and Electronic Engineering of East West University, Dhaka, Bangladesh. 0006-01-01T00:00:00Z