Construction of Automatic Door Bell System with the Object Detection

Automatic Door Bell System

The automatic door bell system is an attractive and much useful circuits in our day to day life. Generally, most of the house owners are using the doorbells. If the visitor comes to the house, first he/she searches for the doorbell. If the house owner is using the automatic doorbell system with the object detection, then the visitor need not to search for the switch of the door bell. Automatically, the sensor will sense the object or the person, hence, the sound will produce at the door. This circuit is very useful for the shorter persons, if he/she can’t press the doorbell switch, then the circuit will automatically sense the person and produce the sound.

What is an Automatic Doorbell System

The “electric bell” is an electromagnet and a mechanical bell. When the electric current is applied to the bell, then it produces the sound. The electric bells are used in many places like in telephone, railroad crossing, Fire, school bells and etc,. Instead of electric bells they are using the electronic sounders.

Electric Bell

The following circuit diagram shows the circuit diagram of an automatic door bell system with the object detection. The circuit consists of an ultrasonic transmitter and receiver modules are used to detect the person. If the person is detected by the IR sensor then the doorbell will be automatically produces the sound.

The frequency of ultrasonic transmitter is about the 40 KHz which we can consider that the ultrasonic waves can transmit continuously about 40KHz. The range of the transmitter is about the one or two meters and the power supply will be moderate. If the transmitter power is less than the one meter, if the person is away from the one meter, then there is a chance to undetected the person. If the rage is very high then it may be cause to false triggering, we can say that if the person is far away from the door, then it is considered as a visitor and produce the sound of the alarm. To overcome this problem the transmitter power is kept to an optimum level.

Circuit Diagram of Automatic Doorbell System

In the circuit the 500kohm variable resistor is used for tuning the sensitivity of the receiver and if we turn this properly then the result will be desired. The output of the circuit is given to the buzzer circuit, which produce the beep sound and act as a doorbell in our case.

In the receiver module, the circuit uses the IC LM324 and it has internally four op-amps. From the four op-amps we are using only three op-amps and the other one is not used, but the requirement is needed in our case. The three op-amps are in the cascaded arrangement to produce high gain and noise free output. There should be a distance between the circuit and door bell, by using the Opto-coupler the distance between the circuit and doorbell are considered.

Electronic Doorbell Circuit

The electronic doorbell circuit is simple and the cost is effective. The circuit consists of various electrical and electronic components like IC 8021-2, NPN & PNP transistor, speaker, resistor of 1K, capacitor, switches and 3V power supply. The IC 8021-2 has inbuilt circuitry to produce the ding dong sound. Every time, the pin-3 is pulled low and it is stored in the IC in the form of bits and as in a ROM. The output sound from the IC can’t drive through the speaker directly, as this puts strain on the device.

Electronic Doorbell Circuit

Thus, for complimentary pair, two transistors are used to amplify the sound in good levels of audibility. At the output end, you can use either a piezo tweeter or 500mW, 8ohm speaker. Hence, we can test the electronic doorbell. During the reserve period the IC consumes normal current which is few microamperes only, thus the switch S1 is closed. If the switch S2 is pushed therefore, the ding dong bell is produced twice. If we press the switch S2 button in second time, when the first time alarm sound is producing thus the alarm sound will be invariably produced.

Applications of Automatic Doorbell System

Some general applications of the automatic doorbell system are fire engines, in telephone, railroad crossing. Fire, school bells and alarm in industrial plants etc.

Advantages of Automatic Door Bell

• The house owner can open the door very quickly
• It is very helpful for short people

In this article, we have discussed about the construction of an automatic door bell system using the object detection. I hope by reading this article you have gained some basic information about the automatic door bell system. If you have any queries about this article or to implement any electrical and electronic  projects, please feel free to comment in the below section. Here is the question for you, what are the applications of the automatic door bell system?