# TMB12A03 buzzer exhibiting unexpected behavior

#### DavidMSchmidt

Joined Jul 8, 2023
3
I have been trying to use a TMB12A03 buzzer in a circuit. It doesn't sound when I think it should. I finally constructed a simple test circuit to try to understand what's going on. When I put a 9V battery across the terminals of the buzzer, it sounds. When I put the 9V battery across the buzzer in series with a 1K resistor, it doesn't sound. (see attached sketch).

What am I missing? The buzzer has the positive terminal marked, and I was careful to make sure to observe the polarity when connecting it to the battery. I measured the resistance across the terminals of the buzzer, and it is in the 1M range--so I wouldn't think adding a 1K resistor in series would make much difference. I also tried several different buzzers from the same batch with the same result, so I know it isn't a failed buzzer.

I downloaded the data sheet but didn't see anything that would indicate why it isn't working. (see attached file).

I'd appreciate any insight or suggestions.

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#### ElectricSpidey

Joined Dec 2, 2017
2,885

Take the maximum voltage and the maximum current and apply Ohm's law, this will give you a better idea of the resistance while operating.

#### BobTPH

Joined Jun 5, 2013
9,276
Measuring the resistance of the buzzer is meaningless because it is not a resistor.

#### sghioto

Joined Dec 31, 2017
5,430
I'd appreciate any insight or suggestions.
I have some of those beepers and a 150 ohm series resistor works fine at 9 volts

Last edited:

#### ScottWang

Joined Aug 23, 2012
7,414

#### Audioguru again

Joined Oct 21, 2019
6,783
The datasheet for the buzzer says, "rated voltage= 3VDC, operational voltage= 1.5-5VDC" NOT 9VDC. Current= 30mA Max at 3V rated voltage.
A series1k resistor with 30mA in it has a voltage drop of 30V then of course the buzzer does not work.

#### crutschow

Joined Mar 14, 2008
34,842
So to operate the buzzer from a 9V battery, you should use a (9V-6V) / 30mA = 200Ω nominal resistor in series.

#### Pyrex

Joined Feb 16, 2022
308
It seems to me, those buzzers are designed to be fed from a voltage source . Add a resistor in series as suggested, and add a 100 uF 10V capacitor across to pins of the buzzer for reliability

#### DavidMSchmidt

Joined Jul 8, 2023
3

I substituted a 150 ohm resistor for the 1K and now the buzzer works. Out of curiosity I measured the voltage across the buzzer and the current through the buzzer with the 150 ohm resistor in series; the voltage was 5.32V and the current was 26 mA, giving an effective resistance of about 200 ohms for the buzzer in that configuration.

#### BobTPH

Joined Jun 5, 2013
9,276
Stop thinking about resistance for things that are not resistors. It is only misleading.