Project12.Passtive Buzzer
===============================

Description
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We can use Arduino to make many interactive works of which the most commonly used 
is acoustic-optic display. The circuit in this experiment can produce sound.

Normally, the experiment can be done with a buzzer or a speaker, while buzzer is 
simpler and easier to use.

The buzzer we introduced here is a passive buzzer. It cannot be actuated by itself, 
but by external pulse frequencies. Different frequencies produce different sounds. 
You can use Arduino to code the melody of a song, quite fun and simple.

Specification
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- Working voltage: 3.3-5v
- Interface type: digital
- Size: 30*20mm
- Weight: 4g

Connect
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.. image:: /img/connect/12_bb.png

Code
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.. code-block:: c

    int buzzer=3;//set digital IO pin of the buzzer
    void setup() 
    { 
    pinMode(buzzer,OUTPUT);// set digital IO pin pattern, OUTPUT to be output 
    } 
    void loop() 
    { unsigned char i,j;//define variable
    while(1) 
    { for(i=0;i<80;i++)// output a frequency sound
    { digitalWrite(buzzer,HIGH);// sound
    delay(1);//delay1ms 
    digitalWrite(buzzer,LOW);//not sound
    delay(1);//ms delay 
    } 
    for(i=0;i<100;i++)// output a frequency sound
    { 
    digitalWrite(buzzer,HIGH);// sound
    digitalWrite(buzzer,LOW);//not sound
    delay(2);//2ms delay 
    }
    } 
    } 



Phenomenon
-----------
.. image:: /img/phenomenon/12.jpg