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Automatic Door Bell With Object Detection

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

Automatic Door Bell With Object Detection Circuit

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.

Important Post: What is Panic Alarm and How its Circuit Works?

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

      1. exactly what relay can do??how to get the sound of bell??? will reciever or transmitter produces ultrasonic sounds or wat???

  1. 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.

    1. i am also thinking to make this as my final year project.Will you please tell me does is work or not?

      1. please try to check the circuit diagram.
        we believe that the components mentioned in the circuit diagram are clear and sufficient.

  2. I’ve been browsing online more than 2 hours today, yet I never found any interesting article like yours. It’s pretty worth enough for me. In my view, if all website owners and bloggers made good content as you did, the web will be much more useful than ever before.

    1. Sir, please give me the detailed information about this. I am beginner. So please give me details.

    1. Dear Sir,

      I’m really happy to read this project and also interested in this product. I need your help please.
      Thank you

  3. 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.

    1. Probably. You will need to refer to the datasheet / instructions for the ultrasonic tx/rx modules you have chosen.

  4. 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.

  5. what is advantage of automatic door bell that it will replace conventional(switch type)? can it detected only human being? or it can detect animal, object ect.please reply me

  6. Sir, is that ic 7555 equal NE555 ? tell me full ic number or send me image of ic 7555. & tell me equal ic of ic 7555….? plz

  7. sir.,
    is this ic 7555 equal to NE555 ?? plz tell me full ic number of IC 7555 or send me image of IC7555….?? tell me equal ic of ic 7555…?

  8. I would like to build this, however, I think you’ve missed a couple of joints or bridges on your second horizontal line from the top. I don’t know if a wire is to connect or jump over others.
    This could be one reason why some people cannot make it work & I’m surprised nobody has caught it.

    I understand the “buzzer” circuit is separate, to keep the values steady in the original circuit. But if the relay itself is being used as a buzzer, it’s not going to be very audible. And this is also probably why people are asking where is the buzzer.

    Can the buzzer relay be connected to a sound chime to act as a push button start?

    From my little search online, it seems this is the ONLY doorbell of it’s type with object detection. So your help would be appreciated.

    Thanks in advance.

  9. This is nice. I want to do it as my final year project work in school. Please what are the shortcomings in the automatic door bell object detector? What are the specific objects it can detect?

  10. Are there any programing involved in this circuit?…If I were to connect a Lcd..where would I connect it???thank you for your reply….

  11. What is the use for the circuit at the left bottom? it is connect to buzzer?
    And one more question…can i replace the adapter with a 12v or 9v battery?

  12. Im having some douts please someone help me out.500.ohm variable resistor?not available anywhere.then where can i connect the speakers and the final one is what is the purpose of ultrasonic transmitter and reciever.please help im stuck in the middle of this project

  13. Our automatic door bell with object detector rings every 5pm everyday even without someone in the door..we check the detector if it has timer but there is none. we’ve been using this for years in the old clinic and it was not happening. but since we moved to the new place the detector ringing every 5 pm .is it possible that there is some circuit problem? we’re very skeptical on this matter coz we think the place is haunted..

  14. our automatic door bell with object detector is ringing even without any object or person in front of it at exactly 5pm everyday.. is it possible ?

  15. y are we using ultrasonic sensors and how does it work?do they have any polarity?please explain me the ultrasonic part….please please please.

  16. This is a good project and i like it. can you help me with its block diagram? its Urgent,im presenting tomorrow!!

    Thank you.

  17. please i wont to construct automatic door bell with object detector as my project,can i get more details and help

    1. what is advantage of automatic door bell that it will replace conventional(switch type)? can it detected only human being? or it can detect animal, object ect.please reply me

      1. The ultrasonic transmiter and reciever is an obect detecting sensor….. yes any object can be dectected to triger the alarThe ultrasonic transmiter and reciever is an obect detecting sensor….. yes any object can be dectected to triger the alarm

  18. Sir,am using this project as a mini project,but I didn’t get the output,can u please send me the video of this project.
    Thank you

  19. When this circuit is at night will start ringing.How we can prevent this?And make the circuit only ring when human is there?

  20. I want to do this project, can you please provide me the detailed list of components used in this project ?

  21. Right here is the right blog for anyone who really wants to understand this topic.
    You realize a whole lot its almost hard to argue with you (not
    that I personally would want to…HaHa). You certainly put a brand new spin on a subject that
    has been discussed for many years. Great stuff, just wonderful!

  22. The is very unique I like it so much, actually I tried myself to connect it many times. but, unfortunately it did not work. it cost much because I choose it as my diploma project.

    thanks for your efforts, but I hope you check it again.

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