Use earplug speakers as piezo speaker

Projects General Guidance
1

I have a newbie question. I'm currently using an NPN transistor to drive a piezo speaker. A capacitor is connected in series between the MCU pin and the transistor's base, and a DAC is connected between this capacitor and the base to regulate the volume. The piezo emits a short beep at variable frequency (pin) and volume (adc).

I want to make another circuit (on another output pin) that connects to earplugs via a 3.5mm jack, with both the right and left channels connected to the same pin. Can I use a similar circuit, perhaps with a limiting resistor to protect the ears in case of wrong volume regulation? What I want to achieve is a similar piezo effect, but through earplugs, with adjustable volume.

With a simple research I've found that speaker is very different from a piezo, so might not work. In case, what could be a simple circuit that I can pilot with a pwm and an DAC (as reference voltage)?

Thanks

2

Do you mean a digital potentiometer?
Which Arduino are you using?

3

Please explain what you mean by "DAC". Post a link to the product page or data sheet, and a circuit diagram. Hand drawn is preferred.

The best approach is to use an audio amplifier module. Very small ones are available from hobby distributors like Adafruit and Sparkfun.

4

There should be a resistor.

Here is a transistor driver circit. It's shown driving a relay but it can also drive a speaker or earphone. It's not a linear amplifier. It will pass-through PWM but it "amplifies" everything to "full volume".

PWM isn't true-analog and it isn't normally used with a DAC or amplifier.

The Arduino can drive a DAC directly. You don't need a transistor in-between. But you DO need a (linear) audio amplifier to drive the earphone/speaker and to have volume control.

Right! Most DACs can't drive a speaker or headphone driectly either. The regular Arduino is rated for a maximum of 40mA from an output pin. From Ohm's Law that calculates as a minimum resistance/impedance of 120 Ohms. Piezos are very -high impedance (and capacitive) so you can connect them directly. You can't directly drive a 4-Ohm or 8-Ohm speaker. SOME headphones/earphones are 12 Ohms or more but most are not.