Salawu & Adetona, 2021 16 www.etrj.com.ng © 2021 Faculty of Engineering, Lagos State University, Ojo. Nigeria. (Print) ISSN 0794-2834 (Online) ISSN 2736-1969 Engineering & Technology Research Journal Volume 6(2) pp. 16-23 (July-September 2021) Modeling of A LDR Based Liquid Level Detecting Device Using Power Function Raifu Ishola SALAWU 1 , Sunday Oladejo ADETONA 2 1 Department of Electrical & Electronics Engineering, Bells University of Technology, Ota, Nigeria 2 Department of Electrical & Electronics Engineering, University of Lagos, Lagos, Nigeria *e-mail: sadetona@unilag.edu.ng Received: 29 th April 2021 Accepted: 13 th May 2021 Published: 5 th August 2021 https://doi.org/10.47545/etrj.2021.6.2.080 ABSTRACT All vehicles require liquid to move from one point to the other; and it is necessary for the driver of the vehicle to ascertain the volume (level) of the liquid in the tank before setting out on a journey, hence the need to know the level of the liquid in the tank. This paper therefore presents modeling and simulation of a sensory device, which evaluates the volume VLQD of any type of liquid in any type of a closed container that has a cross-sectional area A (m 2 ) and height h (m). The main attraction of the approach is that it does not get in touch with the liquid, its simplicity and lower cost. The aim is achieved by using a sensor, Light Dependent Resistor (LDR); which operates on a principle which states that the voltage ELUX in Volts across a LDR is a function of luminance it receives from a light source, Light Emitting Diode (LED). This principle and a power function developed using experimental data were used to model VLQD; which reveals that VLQD in litres is a function of ELUX in Volts. The model of VLQD was simulated for the sake of validation in the Proteus 8.9 professional environment. The results obtained revealed that the proposed model correctly indicated the VLQD in litres in a closed container that its A (m 2 ) and h (m) are known and specified in the model. Keywords: Inverse Square law, Light Dependent Resistor, Liquid, Power function, Sensor 1. INTRODUCTION There are various methods of detecting liquid level in a container. One of these approaches is the one proposed by [1]; which uses the principle of buoyancy that states that a float immersed in a liquid is buoyed in an upwards direction by an applied force equal to the weight of the displaced liquid. As a result, the body moves partially and gets submerged on the liquid surface and covers the same distance that the liquid level moves. The studies in [2], [3], and [4] employed capacitance effects in the development of their various forms of liquid level detectors; which are based on the change of capacitance of the sensor. In this sensor, there are two plates, one of which acts as an insulated electrode; and the other plate acts as the wall of the tank. The value of the capacitance depends upon the level of the liquid in the tank. When the tank is empty, it acts as a low capacitance and when full, it acts as a high capacitance. Another set of liquid level detector are those proposed by [5], [6] and [7]; which are based on the conductivity of probes. In this approach, two electrodes are placed in the liquid and the conductivity of the liquid depends upon the level of the liquid in the container. The liquid detector proposed by [8], [9], and [10] makes used of the ultrasonic sensor; which is made of two units, consisting of a transceiver and a transducer. The liquid level is determined by measuring the trip time difference between a transmitted ultrasonic pulse and its reflected echo. These sensors have the advantage that they are not in direct contact with the liquid and the level measurement is achieved without any physical contact with the liquid whereas, in [9] and [10] liquid level detection uses radar. The principle of radar level detector is similar to that of the ultrasonic sensor; that is, measuring the time require for a microwave pulse and its reflected echo to make a complete return trip between the non-contacting transducer and the liquid level. The transceiver then converts the travel time to distance and presents it as the level of the liquid. Of all level detectors discussed above, only the radar and ultrasonic sensors do not get in contact with the liquid whose height is being measured; hence they do not introduce dirt into the tank. As in the cases of Radar and Ultrasonic detectors, the proposed approach does not get into contact with the liquid, but has the additional advantage of simplicity and low cost. The principle of the proposed approach is similar to that of the ultrasonic and radar sensors in that it does not get into contact with the liquid, but dissimilar in that it does not measure the time require for the illumination of the light and its reflection in a complete return trip between the non-contacting Light Dependent Resistor (LDR) and the liquid level. In this contribution, the quantity of lux received by the LDR causes the resistance of the LDR to