Hi, friends, today i will show how to make buzzer out of relay. Relay is nothing but a switch which is controlled by voltage which we provide. Suppose a relay of 5 volts will act as switch if we provide 5 volts and a little above 5 volts. For this reason it was used as a logic switch in earlier days. In the picture the circuit diagram of relay is shown.Relay is actually single pole double throw(SPDT) switch.

As you can see It has 5 pins. Let us name those pins.
1. The leads to which we provide voltage by connecting them with battery --V1 and V2 (no polarity is concerned )

2. The pin 'I' which is the pin through which we send desired input signal.

3. NC pin(normally closed) with which lead I is shorted when we do not provide voltage.

4. NO(normally open) lead with which I will be shorted when we provide required voltage between V1 and V2

The working principle of relay is very simple. When you connect battery, current passes through the coil and activate the electromagnet which will attract the tip shown in the picture to make NO and I leads shorted.

Step 1: Things Required to Make the BUZZER

Now, come to the main point. Things required to make the switch-

1. Breadboard (optional)


3.connecting wire

4. Battery (according to the rating of relay)

5. battery caps

Step 2: Now Check Which One Is NC and Which One Is NO Pin

Use a continuity tester to test which one is NC and NO.Or you can skip this procedure, that no need for continuity test!

Step 3: Just Connect the 'I' Pin With V1 or V2 As Shown in the Picture

Step 4: Last Step

Now, the ultimate step. Connect V1(or V2) with one pole(+ or -) of battery and take the other pole and touch the remaining two pins.If you hear a buzzing sound while touching a pin then the pin will be NC.

Step 5: Working Principle!

Actually what is happening here is that we are providing voltage between V1 and V2 through NC pin. When relay gets proper voltage 'I' will be shorted to NO pin.So there is no voltage between V1 and V2. So 'I' will again be shorted with NC pin which will again force 'I' to short with NO. This process continues and the frequent movement of the lead will produce buzzing sound. You can see the video. Thank you friends, if you have any question regarding this instructable please comment.

<p>Dear ,</p><p>It is called &quot;Relay chattering&quot; and this is not an alternate of buzzer. Relay coil will weak gradually and will be soon thuuusssssssssssss. </p><p>However, relay description is very good.</p>
<p>U said relay coil will soon weak, could you please explain this statement? Does it mean continues use of relay for this purpose will damage the coil?</p>
Yeah and relay contacts may also damage.
Oh,thank u.

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