We all have a doorbell at our homes. When a visitor comes to our house, he searches for the doorbell switch and then rings it to let us know his presence. If the who came to our house cannot find the doorbell or else if the person is so short that he cannot reach the doorbell, what can be done? How will it be if we use an automatic doorbell which rings as soon as a person arrives at our place? There are no more hassles. The person who comes to our house need not search for the doorbell and press it any more. If we install this automatic doorbell using object detection circuit, the circuit will automatically sense the presence of the person and it rings the doorbell.
Circuit Diagram of Automatic Door Bell:
Using Object Detection
This circuit operates using a pair of ultrasonic transmitter and receiver modules which are used to detect the person and then if the person is detected, the door bell is automatically turned ON when the person is in-front of the door.
The ultrasonic transmitter operates at a frequency of about 40 Kilo-Hertz. That means it continuously transmits the ultrasonic waves of about 40KHz. The power supply should be moderate 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 is kept to an optimum level.
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The ultrasonic receiver module receives the power at the frequency same as that of the transmitter’s so that noise will be eliminated and we get less false triggering. The sensitivity of the receiver can be tuned by using the 500K-ohm variable resistor arranged as a pot in the circuit. By tuning this properly, we can achieve the desired results. The output of our circuit is given to a buzzer circuit which acts as a doorbell in our case. The receiver in this circuit uses IC LM324 which is internally has four op-amps. Out of the four op-amps, we are using only four of them and leaving the other one unused as it is not much required in our case. The three op-amps are used in cascaded arrangement to provide high gain as well as noise free output.
An opto coupler is used at the output to avoid any interaction between our circuit and the door bell.
Assemble the circuit on a PCB as compactly as possible and then attach it to your main door. Thats it! You may provide a power supply using a 9V DC adapter with filtered and regulated output. If the 9V adapter with regulated output is not available, then we recommend you to use a 12V unregulated DC adapter with 7809 voltage regulator.
73 Responses
I am appreciating you for providing this much quality content.
Thanx for detailed description. You provided detailed quality content.
I want To Ask Where We have Connect Buzzer U cant Show Buzzer in Circuit Diagram Thanks
Connect with relay
exactly what relay can do??how to get the sound of bell??? will reciever or transmitter produces ultrasonic sounds or wat???
Very briefly explain soon apply on my house
I hope this circuit works because at the moment i am making this project for our final term. Thank you for giving the exact details for this circuit.
i am also thinking to make this as my final year project.Will you please tell me does is work or not?
Yes, it works perfectly if you do it carefully.
I’m having trouble making this circuit function, can you please help me work on it? Get back to me @ kumsvasanthi@gmail.com
what are the materials that you need to make this automatic door bell?
please try to check the circuit diagram.
we believe that the components mentioned in the circuit diagram are clear and sufficient.
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really good….i will say to my friends about this….
Sir, please give me the detailed information about this. I am beginner. So please give me details.
its very nice and i took it for my mini projects and as well as i fix it to my home
Dear Sir,
I’m really happy to read this project and also interested in this product. I need your help please.
Thank you
Its very nice i’ll make it in my home
Can you please provide the pcb design of this circuit
is it a software project???
hey i wanna do this as my final term project so can u mail me all details to my email id
chrismatt02@gmail.com
where we will connect the buzzer circuit.??? please help me!!!!!
Across the NO relay contacts
sir, is there any polarity for connecting the ultrasonic transmitter and receiver. I’m getting a 8.5V across the transmitter and only 2V across the receiver. But my circuit is not working. pls help me. I’m doing this as my mini project in my college. Its urgent pls help me. Thank you.
Probably. You will need to refer to the datasheet / instructions for the ultrasonic tx/rx modules you have chosen.
Please can you give me the details of how the circuit work, at what meter can he sense the visitor. Is a very nice project…. Thanks.
Sir, can I use NE555 timer instead of 7555. Is there any other adjustments to be made.
what is the value of the diode?does it works?
what is advantage of automatic door bell that it will replace conventional(switch type)? can it detected only human being? or it can detect anything.like animal, object ect.please reply me
Sir, please give me the detailed information about this project…