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Let's say I am trying to embed a Pi WH in my motorcycle helmet. I need thin speakers just by the ear to hear sounds (so, I don't need them to be too loud).
* by the way, piezo speakers won't do it in this project

Since Pi WH doesn't have a 3.5mm audio jack, I think my choices are

  1. use USB speakers
  2. use PWM + audio amplifier + speakers

I can certainly buy a set of USB speakers and just connect to it, but the size matters. so I am thinking #2 would only be my choice.

As far as I researched, I think this is the way to go.

  1. setup Option 1. Use Device Tree Overlay
    https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/pi-zero-pwm-audio

  2. connect a LM386 audio amplifier to one of the PWM pins

    • RPi 5v pin -> VCC
    • RPi ground -> GND
    • RPi a PWM pin -> IN
    • RPi ground -> GND

  3. connect speakers like this to the audio amplifier

  4. remove noises by this config audio_pwm_mode=2

  5. play sounds by aplay command

Please let me know if any of the steps are wrong before I go ahead and buy all of the parts.

update:

I did the followings to just make sure a speaker without an amplifier would sound just enough.. but I hear nothing coming out of the speaker, not even a noise. It's complete silence. Anything I am missing or not doing right?

  1. add dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4 to /boot/config.txt
    dtparam=audio=on is not commented
  2. sudo raspi-config -> Advanced Options -> Audio -> Force 3.5mm ('headphone') jack
  3. reboot
  4. gpio readall shows
    ALT5 | GPIO. 1 | 1 | 18
    and
    | 13 | 23 | GPIO.23 | ALT0
  5. alsamixer and set the volume 100%
  6. hooked a speaker like this (PWM0 = stereo right channel?)
  7. aplay /usr/share/sounds/alsa/Rear_Center.wav or mpg321 some.mp3

enter image description here

kukrt
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1 Answers1

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For small speakers at low volumes, an audio amplifier may not be necessary. I've had success with PWM audio using the now-discontinued CHIP computer (which should be similar to the Pi) and these speakers from Adafruit without an amplifier in between. If you happen to have the right parts lying around, I would suggest trying this setup before ordering the amplifier.

Also, I would be wary of using an amplifier from AliExpress; you might be better off with this one from Adafruit. It uses less power, which could be useful for a project like yours. Also, it has both the L and R channel, so you could have stereo sound.

Brooke Chalmers
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