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How to Set the Frequency of Piezoelectric Buzzer

A piezo buzzer is an electrical component that creates a sound when a voltage is applied to it. Buzzers are normally manufactured to produce a specific frequency when given this voltage. The frequency is noted on the package or on the manufacturer's website. It can also be determined with the use of a digital multimeter, oscilloscope or frequency counter.

To set the frequency of a piezo buzzer, connect it to the voltage recommended by the manufacturer. If the buzzer has a built-in driving circuit, set the frequency by following the manufacturer's directions. For example, add the recommended voltage, but also add a potentiometer. The potentiometer has a variable resistance, so when its knob is turned, the current to the buzzer will change and this in turn will change the frequency. Alternatively, set the frequency of any buzzer by using a driving circuit.

Things You'll Need

Piezo buzzer
741 op amp
100k-ohm potentiometer
2 4.7k-ohm resistors
22k-ohm resistor
10 uF capacitor
Battery
Battery holder
Solderless breadboard
Jumper wire
Digital multimeter

Instructions

- 1
  Study the data sheets for the op chip and identify the numbering system for the leads. Normally, one side of the chip is marked with a notch or circle, indicating that lead one is to its left. Leads two through eight are counterclockwise from the first.
- 2
  Insert the buzzer into the solderless breadboard. The plus and minus pins of the buzzer must be in different columns. The best way to do this is to place the buzzer so that its plus and minus pins straddle the opening between the top and bottom sections of the breadboard. Insert the 741 chip the same way, so that all eight of its leads are in different columns. The chip must be a slight distance away from the buzzer.
- 3
  Establish one of the rows at the very top of the breadboard as ground, or zero voltage. If the breadboard does not have a row set aside for voltage connections, choose one of the columns as ground, instead. Similarly, establish a row or column for positive voltage. Insert the black wire of the battery holder to ground, and add the red lead of the battery holder to the positive voltage row or column.
- 4
  Wire the minus side of the buzzer to ground. Do this by inserting one end of a jumper wire into the column that the negative side is in, and then placing the wire's other end into the one of the holes in the ground row. Similarly, attach pin 4 of the op to ground.
- 5
  Add a wire between the plus side of the buzzer and pin 6 of the chip, so that they are connected. Connect pin 7 of the chip to the same row that the red lead of the battery holder is in.
- 6
  Wire pin 2 of the op amp. Do this by first inserting one end of the potentiometer or pot to this pin, and placing the other end of the pot in the column of pin 6. Choose another opening in pin 2's column, and attach one end of the capacitor to it. Place the other end of the capacitor at ground.
- 7
  Wire pin 3 of the op amp. First, place one end of the 22k resistor to pin 3, and place its other end at pin 6. Next, choose one spot on the breadboard, and connect the two 4.7k resistors in series, so that the right side of the first is in the same column as the left side of the second. Attach the left side of the first resistor to the row that the red lead of the battery holder is in. Attach the right side of the second resistor to ground. Add one end of a jumper wire to the same column where the two resistors are joined, and place the remaining end of the wire to the op amp's pin 3.
- 8
  Add the battery to the holder, and move the knob of the pot back and forth. The buzzer will change its frequency. Test the frequency change by first placing the multimeter on the frequency setting. Then attach the multimeter's red probe to the output of the buzzer's plus side, and the black probe to ground. One way to do this is to add a wire to the column that the buzzer's plus side is in, and then use alligator clips to connect it to the red probe. Do the same to connect the ground side to the black probe.

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