electronic crank mechanical doorbell circuit schematic

Crank Doorbell Circuit Schematic

Here is an interesting hobby circuit of a “crank” door bell! The circuit is built around a timer 555 and a musical piezo-buzzer. The circuit works off 9 volt battery supply. One 9volt PP3/6F22 compact battery is enough for powering the whole gadget.

Timer IC (NE555) is wired in monostable mode to produce a time out o some seconds. The output of the timer is fed to the input of the piezo sounder through a diode D1. Capacitor C2 works as a buffer. RC components R2, C1 sets the monotimeout of the timer IC NE555. An ordinary low voltage small dc motor is here used as the crank switch.

In prototype, one small “disc motor” from a discarded cd drive (optical deck) was used. Even a slight rotation of the motor shaft will produce sufficient counter emf to enegize the LED(S) inside the ac opto-coupler PS2505. As a consequence, phototransistor inside PS2505 conducts and there by it pull down the trigger input (pin2) of IC NE555. The result is a loud but pleasing musical tone output from the piezo sounder for a finite duration, here around seconds.

One can easily replace the musical buzzer with an EM relay for switching external loads. A 9 volt/600 Ohm relay is preferred for this modification. The circuit can also be used as a two wheeler security aid which senses the wheel rotation of a parked vehicle and sounds an alarm to alert the owner. With a little skill, one can easily attach the crank mechanism (like the dynamo-wheel assembly) to any vehicle. However, for burglar alarm application, a latching output circuit is highly recommended.

Mechanical Doorbell Circuit Schematic

electronic crank mechanical doorbell circuit schematic


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  • Amin

    I keep all bolts locked at all times. When I shewor my little one 20 months is in a play area with the baby gates and is entertained with a movie and toys and snacks. She knows how to turn door knobs and it wouldn’t take long for her to try to reach a lock. I don’t answer the door to people because it’s usually crazy people. I’ve had a guy knock at my door at 4 am high on drugs trying to ask me to hang out with him and get high. I don’t smoke or drink or do drugs and didn’t know that guy at all. He kept trying to say he knew me. At the time my little girl was only a few months old. There was another time a crack head lady was knocking at my door saying she was selling cookies. She didn’t have any cookies in her hands and I wouldn’t buy them from crackheads anyway. I told her she had the wrong place and to go away. Religious people knocking on my door annoy the shit out of me. Stop bothering people. Leave a brochure and if I’m interested I’ll call your church or go. Otherwise leave people alone. In my apartments you have to be careful. There are people on drugs, shady pedophile looking people, people that just don’t care about anyone, etc. There used to be these two little girls from Brasil. One was 8 and one was 3. They would walk all over the apartments alone and the 8 year old had a very trashy mouth and would say inappropriate things to kids and adults both. One time she came up to me and she had her little sister with her. The little sister was just in some panties and they had been walking all over the complex! I told the older girl she should take the little one to go put clothes on and to look out for her little sister while they are walking around the apartments.

  • ODin

    Is this really working? Does any body tried it?
    Thank you..

    I hope this circuit is working cause i wanna try it

  • r.rgfhrdsty


  • kamal das

    it is fine to meet you sir. it is an excellent circuit.

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