How to choose a buzzer?

To produce the right sound at the right frequency, we need to choose the buzzer wisely. Some buzzer can only produce sound at low frequency which as for my project, it will not work effectively to measure hearing threshold.

There are many different kinds of buzzer to choose, first we need to know a few parameters, such as voltage, current, drive method, dimension, mounting type, and the most important thing is how much SPL and frequency we want.

Operating voltage: Normally, the operating voltage for magnetic buzzer is from 1.5V to 24V, for a piezo buzzer is from 3V to 220V. However, in order to get enough SPL, we suggest giving at least 9V to drive a piezo buzzer.

Consumption current: According to the different voltage, the consumption current of a magnetic buzzer is from dozens to hundreds of mill amperes; oppositely, the piezo type saves much more electricity, only needs a few mill amperes, and consumes three times current when the buzzer start to work.

Driving method: Both magnetic and piezo buzzer have self drive type to choose. Because of the internal set drive circuit, the self drive buzzer can emit sound as long as connecting with the direct current. Due to the different work principle, the magnetic buzzer need to be driven by 1/2 square waves, and the piezo buzzer need square waves to get better sound output.

Dimension: The dimension of the buzzer affects its SPL and the frequency, the dimension of the magnetic buzzer is from 7 mm to 25 mm; the piezo buzzer is from 12 mm to 50 mm, or even bigger.

Connecting way: Dip type, Wire type, SMD type, and screwed type for big piezo buzzer are usually seen.

SPL: Buzzer is usually tested the SPL at the distance of 10 cm, if distance double, the SPL will decay about 6 dB; oppositely, the SPL will increase 6 dB when the distance is shortened by one time. The SPL of the magnetic buzzer can reach to around 85 dB/ 10 cm; the piezo buzzer can be designed to emit very loud sound, for example, the common siren, are mostly made of piezo buzzer.

week 6

I met Mdm Naza ealier (20/2/2012) to showed her my Arduino buzzer circuit. She asked me the specification for the buzzer(the rated frequency) which I overlooked. So the new task for me is to find the suitable buzzer that can produce sound according to the frequency that I want. Herewith is some of the specification that need to be take into consideration;

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Specifications:

Rated Voltage: A piezo buzzer is driven by square waves (V p-p).

Operating Voltage: For normal operating. But it is not guaranteed to make the minimum SPL under the rated voltage.

Consumption Current: The current is stably consumed under the regular operation. However, it normally

takes three times of current at the moment of starting to work.

Capacitance: A piezo buzzer can make higher SPL with higher capacitance, but it consumes more electricity.

Sound Output: The sound output is measured by decibel meter. Applying rated voltage and square waves, and the distance of 10 cm.

Rated Frequency: A buzzer can make sound on any frequencies, but we suggest that the highest and the most stable SPL comes from the rated frequency.

Operating Temp.: Keep working well between -30℃ and +70℃

week 5

Last Thursday (16/2/2012), I had a brief discussion with Mdm. Naza regarding my concern about my project. As I mention last week, the progress is out of the path so yeah, I am a liltle bit freak out!

Mdm Naza then suggested me to change the program from Assembly to Arduino UNO. Next, due to the changes I've made, I am going to use a piezo buzzer circuit to produce the sound frequency. (The decicion has been made, I'm going to change the circuit to more simpler!)
The circuit will be modified by the Arduino program. So, throughout the week, I've been doing some research on Arduino UNO as well as the buzzer circuit that will be used together with Arduino. If things goes well, I would like to add up other features like a switching(for patients to notify if they heard the sound) as well as the LCD display(to display the frequency value).

Arduino UNO

Theory of piezo buzzer

The piezo buzzer produces sound based on reverse of the piezoelectric effect. The generation of pressure variation or strain by the application of electric potential across a piezoelectric material is the underlying principle. These buzzers can be used alert a user of an event corresponding to a switching action, counter signal or sensor input. They are also used in alarm circuits. 

The buzzer produces a same noisy sound irrespective of the voltage variation applied to it. It consists of piezo crystals between two conductors. When a potential is applied across these crystals, they push on one conductor and pull on the other. This, push and pull action, results in a sound wave. Most buzzers produce sound in the range of 2 to 4 kHz.

The Red lead is connected to the Input and the Black lead is connected to Ground.

Week 4

Ok.. this is really like a wake up call for my project.. time is running out and i haven't start with my circuit construction yet..

Last thursday (9/2/2012), I had a brief discussion with Sir Zubir regarding my project where i did mention last time that i have a problem with the programming. Since my circuit is going to use Assembly Language to run it, Sir Zubir remind me that i will faced a problem if there is a problem with my project. As i don't really understand the Assembly Language, therefore it will be hard for me to troubleshoot my circuit. I also had a short discussion with my supervisor, Mdm Naza and she suggest me to find another circuit while Sir Zubir suggest me to use simpler program.


# i'm changing the circuit as well as the program use so i need to buy all the component all over again.

Week 3

As Salam..

As for the third week, the progress is getting a little bit slow i can say.. I haven't start with the circuit construction yet.. but i'm planning to do it sooner.. 

I didn't get the chance to have a proper consultation with my supervisor this week but I did manage to have a quick discussion with her right after our class session. The discussion is all about the programming that is going to be used for my project. We still trying to look for a simpler language for the programming and a further discussion is needed.

Next, as i mention in previous post, i wanted to go to Jalan Pasar sometime on last week to check out the electronic component needed for the circuit construction. So, I went to Jalan Pasar on saturday. I'm having a problem of getting a Mux 4051. Planning on going there again some time on next week. 

Below is some of the picture of electronic components that i've bought.