If there is no test equipment, how to test the performance of electromagnetic passive buzzer?
users do not have test equipment, they can test whether the electromagnetic passive buzzer is suitable for use through the following simple methods:
1, take a finished PCB actually used by the user, or a PCB with a complete circuit as long as there is a buzzer sound source output part.
2. Confirm whether the circuit parameters on the PCB are correct:
First, whether the circuit power amplifier part is correct, refer to Figure 1, where diode IN4148 can be absent;
Second, confirm whether the frequency of the signal generated on the PCB matches the selected buzzer (the signal frequency is preferably 50% duty cycle square wave, otherwise some parameters of the buzzer will be affected), the rated frequency of the selected buzzer must be the same as or before the actual use frequency, and be careful not to select the buzzer with the lower frequency. For example, if your PCB output frequency is 2700Hz, you must choose a buzzer with a rated frequency of 2700Hz or 2600Hz. Never choose a buzzer with a rated frequency above 2700Hz. The bandwidth of most buzzers is generally between 100-200Hz, and preferably not before the rated frequency;
Third, confirm whether the power of the signal source on the PCB is sufficient to saturate the triode of the buzzer power amplifier part. If not, the resistance value of R1 in Figure 1 must be reduced, and the resistance value of R2 must be less than the resistance value of the buzzer or 0 ohms.
Fourth, confirm whether the voltage of the buzzer power amplifier part on the PCB matches the rated voltage of the buzzer selected, if the voltage is too small, the parameters of the buzzer will not reach the specifications.
Fifth, lead the wire from the part where the buzzer is connected on the PCB to the test fixture, and pay attention to the wrong connection of the positive and negative poles. The electromagnetic passive buzzer has clear positive and negative poles and cannot be connected wrong.
Sixth, if there is no sound pressure meter, the minimum standard seal sample with acceptable volume can be compared and identified by listening; as the human ear will be fatigued when listening for a long time, and there will be a large deviation in listening under fatigue, this method of testing will be quite controversial, so it is better to use a sound pressure meter if conditions permit (the sound pressure meter commonly used in the market is TES1351B around 300 yuan, and if the readings of sealed samples are used for comparative testing, it can completely meet the requirements)
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