Piezo Tranducer Sensor

Guys i need help with my circuit, it isnt working this is the circuit i have. i cannot get an output when i hit the vibration sensor at pin 3(output) any help please?? I used a 2n7000 instead of BS170. What could be the problem please??

its to pick up engine vibration, the piezo transducer specifications are Piezo Transducer 27mm/4.2kHz
Resonant frequency: 4.2kHz ±0.5kHz
Impedance at resonance: 500Ω
Capacitance: 14nF ±30%
Maximum input voltage: 30V p-p
Operating temperature: -20°C to +70°C.

Did you use a piezo transducer (speaker) or a piezo beeper that has an oscillator built in?
It will not work with a beeper.

it is a piezo transducer (speaker).

You know that the pinout on the BS170 is reversed from the 2N7000, right?

yes i did that but still not working??

At this point, it is just a guess at what might be wrong. If you want more help, you have to provide more information.

What are you trying to accomplish?
You only provided part of the schematic; post it all.
What have you tried and what have you found?
What does the circuit do and what does it not do?
What is your power supply?
Is your assembly on a perfboard or a solderless breadboard?

Post some closeup pictures of your assembly.

I'm trying to use it to measure the vibration from an engine, which when sensed i would like it to have a sound on a speaker at the pin 3 i dont wanna go beyond the circuit, it is a 9v to 0v voltage supply. but i dont even seem to get a signal at pin 3 when using a oscilloscope.

it is on a prefboard.

There are people here who can help, but no one can guess what is wrong with your circuit without knowing what you have done. Until you provide pictures, all I can do is ask more questions.

Why do you think you should be able to connect a speaker to pin 3 and hear anything? The 555 is not set up as an oscillator in this circuit.

The 555 is not an audio amplifier. It is a timer.
The circuit you found will not do what you want and I don't think it will do anything.

Here is a report on the complete circuit that you have posted only a part of. Even though the report is not very well written, maybe it will help.

I see.
It is a car burglar alarm circuit.
When I close the door of my car then the car beside my car makes a siren sound because it has this extremely simple circuit that detects the vibration caused by the door on my car closing. It makes many false alarms.

Does the cover page of the report mean that this is a project done by three engineering students who are in their fourth year of college?

And are earth "quacks" common in India?

And is plagiarism rampant among engineers in India?

Okay i can get some signals at the moment but i need another help i want to display my output using leds, meaning low vibration will display green led while red to display green led any suggestion on circuits??

My suggestion is for you to post a schematic of what you have built. Otherwise, there is no way for anyone to suggest anything sensible.