Door bells are needed in all homes, when visitors pay a visit to our homes; the doorbell is their first contact device they use to draw attention of occupants. They intend ring the doorbell by location it switch to let us know there?s a visitor at the entrance. Some time it becomes difficult for some people to identify where the switch is positioned. This equally affects children who are too short to reach the doorbell switch, especially when they return from school.
Therefore the need for to introduced automatic doorbell using an object detector was critical in this project. The system need to be highly reliable as compared to Push-Switch type of doorbell.
The introduction of Automatic doorbell using object detection became more critical, because it will eliminate the inconveniences associated with Height, Search and press switch. In this case, the circuit will automatic sense the presence of the person and rings the doorbell.
This sensor switch helps to ring door bells automatically if any person or object is rear to the door.
Literature review :
The necessity for some means by which someone on the outside of a door could notify someone on the inside of his presence has been recognized for centuries. The earliest solution to this problem consisted of the simple expedient of knocking on the door with one's fist. As the human race grew in wisdom and technical sophistication, new and subtler methods were invented. The first of these was the mechanical door knocker, which saved man untold pain from bruised knuckles. Then with the advent of electronics came the electrical door bell which was coupled with principle of electromagnetism (make and unmake) thereby causing vibration which rings the bell, the evolution of which over the past two decades has seen the invention of a number of methods capable of detecting the approach of a person to a door at a distance and triggering the production of an appropriate sound on the inside of the door. Unfortunately, all such methods so far suffer from disadvantages which have prevented their widespread application to residential doors.
These methods can be divided into three categories on the basis of the principle used to detect the approaching object. The first category involves the use of a mechanical switch which is activated when the person steps on it. The second involves the use of a photoelectric sensor and a light source arranged so that the person casts a shadow on the sensor as he approaches the door. The third involves some type of capacitance proximity sensor which detects the change in capacitive coupling between a metal sensor plate and ground, or between two plates mounted on or near the door, that results when a person approaches them.
None of the three categories has achieved wide acceptance in residential applications, principally because they are all difficult to install, limiting their usefulness primarily to those instances when they can be built in during the construction of the building.
The mechanical switch method requires that a mat containing many such switches be placed in front of the door in such a way that anyone approaching the door must step on it. Not only are such mats highly anaesthetic, but it must be connected to the sound producing unit inside the house, requiring that a hole be drilled through a wall. This sort of installation is beyond what most home owners have the time or skill to attempt, and is therefore usually done by professionals, greatly increasing total cost.
The photoelectric method requires that a light source and photo detector be mounted on either side of the path leading to the door. Here again, installation is usually done by professionals, and unless it is possible to hide the units in shrubbery, the light source and detector can be even more anaesthetic than a mat.
Installation of a doorbell based on a capacitance proximity sensor is somewhat simpler than that of a mechanical switch or photoelectric unit in that the entire device can be mounted on the inside of the door. However, in order to obtain even the minimal detection range of two feet, metal sensor plates of several square feet must be used, and while these cannot be seen from the outside they are painfully obvious from the inside.
In order to overcome the disadvantages of the methods discussed, it is clear that the ideal automatic doorbell would consist of a single small battery-operated unit. Installation would consist of driving a nail on top of the door and hanging the unit to it. The automatic doorbell herein described seeks to meet these criteria.
Using Multisim Software
Circuit Diagram of Automatic Door Bell Using Object Detection
Prototype circuit board simulator and component bill list
Internet research and other references from electronic circuits theory books.
In this project, we hope that the automatic doorbell will function well.
Actually this circuit operates using a pair of ultrasonic transmitter and receiver module which are used to detect the person or object.
So, in order to detect the person, we have to use a very moderate power supply such that the range of the transmitter is only about one or two meters.
If the transmitting power is less than one meter, then there is a chance that the person who is one meter away is not detected.
Also, if the range is set to be very large, then it may lead to false triggering, meaning that, the objects far away from our door are considered as the visitors and the alarm rings.
This can be a nuisance for us if the alarm rings for every object or person far away. So, to avoid both the problems, the transmitting power will be kept to an optimum level.
Furthermore, to utilize the circuit very well to make it functioning, we employs the following;
The reason to use the Multisim software is because it easier to make the simulation of the circuit. Moreover, majority of us know how to use the Multisim based on this circuit. This software is also commonly used by the student to simulate their own project.
2. Prototype board:
Prototype will help us to practically test the circuit before we print out the circuit on PCB, the reason is, it is easier to troubleshoot and also can make any changes before the final construction.
After testing the circuit on prototype board and achieve a good result, we can now print out the circuit on the PCB. Then, we solder the components on PCB. Thus, this is our final step in finishing the project