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..we planned to use a piezo buzzer for our project but our instructor rejects it..he says that why not use a 5v speaker than a piezo buzzer.,he also says that we use the 555 timer to generate sound.how?should we just replace the piezo buzzer by the speaker in the circuit?

and from what i have understand from him piezo generates its own sound while speakers don't?i thought at first they are the same they just differ in size.if that so how can we generate sound using the 555 timer?

whats the difference of the piezo buzzer and the speaker?

1) Set up a 555 timer as an astable oscillator.

2) Connect either (a) a high impedance loudspeaker >80Ohms or (b) a low impedance loudspeaker with a series resistor or (c) a low impedance loudspeaker driven from the 555 timer output through a simple amplifier stage.

The basic differences between a loudspeaker and a piezo "buzzer" are that the former is an electromagnetic device, the latter a piezoelectric device.

Piezo buzzers tend to work best (loudest) at a particular self resonant frequency and so can be tricky to drive to get the loudest sound from them. Driver circuits can be a bit specialised and often include built in oscillators with resonant circuits to try to tune the oscillator the piezo sounders natural self resonant frequency. Some piezo buzzers have all the electronics already built in to do this, others are bare piezo sounder elements and you have to build the driver round the sounder disc.

Compared to piezo sounders, loudspeakers are pretty much a no brainer. You have to drive them from a relatively low impedance source and don't put any DC current through them: it biases the cone to one end or the other and so limits the dynamic range and may also easily burn out the voice coil. In other words, capacitively couple them to the driving signal source.

Apart from that they need little special care and feeding and they can generate an adequate sound level over a very wide frequency range.

From here on, Google and Wikipedia are your friends:

http://en.wikipedia.org/wiki/Buzzer

http://en.wikipedia.org/wiki/555_timer_IC

Search CL for 555 timer

and read this thread:

https://www.circuitlab.com/forums/basic-electronics/topic/2zndkjpx/power-failure-alarm-circuit_please-help/

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