ELECTRONIC PROJECT REPORT (SKEE1012)
Title : Darkness Sensor Control
Name : Chew Jun Jie (A18KE0040)
: Choong Zhen Yin (A18KE0044)
: Goh Kean Wei (A18KE0062)
: Hafiz Haziq bin Amizi (A18KE0066)
: Haqim bin Hanafi (A18KE0068)
: Abdalla Mohamed Moustafa Ahmed Eldessouki (A17KE3013)
Course : SKEE 1012
Section : 10
Lecturer : Dr. Zolkafle bin Buntat
Abstract
This study investigates on how to build a circuit that based on the title ‘darkness sensor controller’. Investigation on how the circuit would function has also been done by this project. This project also investigates on how Light Dependent Resistor (LDR) works and how can it be applied into our daily life activities. Things in real life that could use this circuit included street light.
Introduction
‘Darkness sensor controller’ is also known as automatic street light sensor [1]. Darkness sensor controller basically is a powerful circuit that allows the light to be turned on when the intensity of the light from surroundings are too low. This could function as automatic switch to power on and power off the circuit depends of the intensity of the light in the surroundings. The benefits of using this circuit instead of a normal circuit is that this circuit could save energy as it will automatic switch off the light if there is no need for the street light to light up. The main components involved in this project is Light Dependent Resistor (LDR).
Light Dependent Resistor (LDR) also known as a photoresistor, is a light-controlled variable resistor [2]. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.[2] A photoresistor can be applied in light-sensitive detector circuits, and light-activated and dark-activated switching circuits.[2] A photoresistor is made of a high resistance semiconductor[3]. In the dark, a photoresistor can have a resistance as high as several megohms (MΩ), while in the light, a photoresistor can have a resistance as low as a few hundred ohms [3]. If incident light on a photoresistor exceeds a certain frequency, photons-absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band [3]. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance [3]. The resistance range and sensitivity of a photoresistor can substantially differ among dissimilar devices [3].
Theory and Analysis
There are various types of light sensors available such as photoresistors, phototubes, phototransistors and so forth. But, light dependent resistor (LDR) is preferable to be used as a light sensor in light sensor circuit as it is a passive element which does not produce any electrical energy. Besides that, light dependent resistor (LDR) is rugged in nature which means it can be used in dirty and rough external environments. Light dependent resistor, a photoresistor, is a variable resistor that is controlled by light intensity. Resistance of light dependent resistor (LDR) will change along with the intensity of daylight. To further exemplify, LDRs are made of high resistance semiconductor material, Cadmium Sulphide that exhibits photoconductivity. For example, LDR exhibits a high resistance of around a few Mega ohms during the night time and vice versa.
Transistor act as an important role in this project. There are two different categories of transistors which is NPN transistor and PNP transistor. NPN transistor is used as a switch in this circuit to make the stuffs easier which allow the current to flow in the night time automatically. For example, if the voltage through the base of transistor is greater than specific voltage needed to switch on the LED, the current will be allowed to pass through the emitter of transistor. On the other hands, low voltage will be sent through the collector of transistor.
Experimental procedures
The aim of the project is to find a way to reduce energy wastage. Nowadays, many countries rely too much on non-renewable energies such as biomass, oil and natural gas. These sources of energies are limited and are about to be completely exhausted by mankind in the near future. Hence, to solve the problem, renewable energy sources must be used or even better, reducing the amount of energy usage. Through this project the idea is to create a light source that switches itself off during the day and turns on in the night. This is because humans generally are able to see without problem during the day and only require light when it is dark. By doing this, 50% of the daily energy usage could be saved indefinitely. To achieve this goal, a Light Dependent Resistor (LDR) is needed. This component has high resistance in the absence of light and low resistance in the presence of light. Therefore, a circuit diagram is designed so that it can switch on in the absence of light and switch off in the presence of light.
Results and Discussion
In this project, we use Light Dependent Resistor known as LDR. An LDR is a component that has a (variable) resistance that changes with the light intensity that falls upon it. This allows them to be used in light sensing circuits. The most common type of LDR has a resistance that falls with an increase in the light intensity falling upon the device.
For the transistor to turn on or to allow current to flow from collector to emitter, the voltage at the base should be above a certain threshold voltage.
We used a resistor in series with the LDR (basically a voltage divider) to convert the change in resistance of the LDR to change in voltage. This change in voltage at the common point between LDR and resistor is used the trigger the transistor by connecting it to base of the transistor.
So, when the light intensity decreases, the resistance of the LDR increases. As this resistance increases in relation to the 50k Ohm Resistor, which has a fixed resistance, it causes the voltage dropped across the LDR to also increase. When this voltage is large enough it will cause the Transistor to turn on and flow the current. Thus, the LED will turn on.
Conclusion
This darkness sensor project is useful for saving costs. Additionally, it can also save energy and save the earth. For example, this project can be used on street lights. When the night appears, the light will open on its own and will be closed when the sun rises. It is efficient as no workers are needed to control the switch.
Besides, LDR is a useful device when we want to make a project in relation to light. Despite the darkness sensor project, there is a lot thing we can do by using LDR such as morning alarm, light detector and many more.
Reference
- Riyazbateman (10th December 2016),from: https://www.quora.com/How-does-a-dark-sensor-work-Could-anyone-explain-the-use-of-transistor-in-it-easily
- Resistor guide (2018) Photoresistor, from: http://www.resistorguide.com/photoresistor/
- John (29th October 2017) Photoresistor-Symbols, Working Types and Application, from: http://www.circuitstoday.com/photoresistor