Buzzer Oscillators

We all know that buzzers generate sounds. The question is, how do you extract an electric oscillating signal from a buzzer? This instructable shows you how you can make an oscillator with the use of a buzzer.

All you have to do is simply connect a buzzer in series with a resistor (make the resistor buzzer series circuit).

I connected four series 1 kohm resistor buzzer circuits in parallel and two series 10 kohm resistor buzzer circuits in parallel because I did not want to buy a battery for each of the six series resistor buzzer circuits that I made. However, you only need one series circuit to see how this idea works.

Components: buzzers, resistors (10 ohms, 100 ohms 1 kohms, 10 kohms, 100 kohms), matrix board or piece of cardboard, wires, battery harness (9 V, 7.5 V, 6 V or 4.5 V), power source (9V/1.5 V/AA/AAA batteries).

Optional components: solder, connectors, sticky tape, blu tack, 1 mm metal wire (you will need a tool to cut this wire - wire stripper or pliers).

Tools: wire stripper, scissors.

Optional tools: soldering iron, pliers.

The circuit is very simple. It consists of a resistor connected in series with a buzzer. I used the coil component to represent the buzzer because my old PSpice student edition simulation software version 9.1 does not have a buzzer component.

When the buzzer is ringing/buzzing the current across the buzzer is constantly changing and because the voltage across the resistor equals I*R (series circuit current multiplied by resistance) the output voltage Vo1 varies with time. You can see this change in the resistor output voltage Vo1, which is equal to:

Vo1 = Vs - VR1

= Vs - Ibuzzer*R1

(Where: Ibuzzer = Vs / (R1 + Rbuzzer))

The only question that remains is how do you choose the resistance value:

1. If the R1 resistance is too low, you might think that the voltage across the R1 resistor (VR1) will be high because of the high series current (current across the R1 resistor and the buzzer). However, the voltage across the R1 resistor will be low because of low resistance.
2. If the R1 resistance is too high, you might think that the voltage across the R1 resistor (VR1) will be high because of the high R1 resistance. However, the voltage across the R1 resistor will be low because of low series current (current across the R1 resistor and the buzzer).

The best resistance value is one that is equal to the average resistance of the buzzer. However, calculating the average resistance of the buzzer is not an easy task because the buzzer is made from a coil that turns ON and OFF every few milliseconds.

What I did was try different resistor values for different buzzers to see which resistor value gives the maximum varying voltage output.

I made the circuit on a piece of cardboard. I twisted the wires with my fingers but you can use pliers. I also used a 1 mm metal wire that you can see in the photo. The green, white, yellow, and orange wires are the outputs. I used 2-watt resistors. You do not need to use such high-power resistors. I only used those big high-power resistors because the colour codes are easy to read in the photos. However, because the power of a component equals V*V/R a low-resistance component might will dissipate high power. Thus if you use a high-current buzzer and a low-value resistor (for example - 10 ohms) you might need a big high-current resistor.

I used Hantek 6022BE USB Oscilloscope to record electrical signals from buzzers.

The first four plots are for four 1 kohm series buzzer circuits and the last two plots are for the two 10 kohm series buzzer circuits. You can see that the maximum varying voltage was for 10 kohm resistors. Another option is to use a potentiometer (variable resistor) to find the optimum resistor value that will maximise the varying voltage.