Pi Zero Wireless Speaker

From here I will have to wait at least a few weeks for the LM386 amplifier to come in the mail (I ordered two from different stores, lets see who wins the race...). I am still having thoughts about what to do with the switch, I could use it to enable streaming audio.

I have also considered making it power up from the switch, making the SD card read-only (overlay filesystem) and automatically start streaming whenever the pi boots up.

I haven't looked into what software there is to drive the speaker from my phone, if anyone has a suggestion, drop a note in below. (VLC remote?)

For now, as a bedside speaker this should work fine with quiet audio.

Nothing is glued or stuck down, I also intend on addressing that in the final design as well.

This was the biggest step, getting it all a lot smaller and fitting in the small gap in front of the speaker.

First was to get the strip the parts off the USB sound card, the 3.5mm jacks were the easy part and the USB jack, even though the shield was not soldered in. In the end I got it loose enough to use metal fatigue (wobble the jack back and forth) the the pins broke.

With that out of the way, time to solder everything to the Pi Zero. I used this guide to solder the USB sound card directly to the Pi: https://www.grappendorf.net/tutorials/nerves-pizero-edimax.html

After a lot of de-soldering and soldering, I gave it a quick test, nothing fried, fortunately. Next I soldered the 5V straight to where the header should go.

After soldering the resistors in place and the speaker to the USB sound card, time to give it a final test before stuffing it all in the case. All worked again.

Finally I made the USB sound card the default alsa device using this guide: https://nixingaround.blogspot.com/2016/11/raspberry-pi-zero-usb-audio.html

And finally, all stuffed in, case screwed down and boot up the Pi, winning!

I weighed up whether I should use 5v directly in or use the original nest mini power supply. I could easily go down to the shop, grab the right barrel jack size and go from there, but I do have a few 5v UBECs sitting around for exactly this sort of project.

As these were cheapies off eBay, I wanted to make sire the voltage output from 14V came down to 5V OK. I'm glad I tested the voltage first, the UBEC I grabbed had 12V out, even though it was labelled 5V. Lucky save.

After I found another that did have a clean 5.1V output, I moved onto the test phase. I knew I didn't have an amplifier and the cheap USB sound card would not be able to drive it, and I was right, test from my PC showed it was really quiet. When I did hook it up the USB chip became quite hot, I would assume the chip is not designed to drive this speaker. A quick check with the multimeter says 4 ohms.

I jumped on eBay to order a small LM386 mini amplifier, once I have that this set up should be a lot louder.

As part of this phase I soldered the UBEC straight to the back of the barrel jack PCB. Earlier investigations found no electronics or odd connections here, so it was easy enough to get power straight to the UBEC.

I wanted to make sure I also got mixed mono from the stereo output from the USB sound card. I tried a few values, but the only one I felt safe using and gave me barely enough audio was 100ohms from left and right output with mono from where they joined.

Over to the Pi, as I am running this headless, I followed this guide to get it to connect to my home WiFi and run the ssh daemon: https://www.raspberrypi.org/documentation/configuration/wireless/headless.md

I logged into the pi over the network and rand `speaker-test` as well as installing `mpg123` and streaming an online radio station. After some adjustment of the audio device it worked fine, albeit, very quiet. But it all works.

As a side note, the mic switch when showing orange is open circuit to in side of the switch, when closed shorts to ground. This could be used wired to a GPIO pin on the pi in the futue.

14v to 5v to Pi 0 W to USB Audio to speaker.

I used the teardown instructions on ifixit to get the Mini apart. After getting in, I decided the strip out the main board, antennas and electronics and see what parts I had available.

ifixit teardown guide: https://www.ifixit.com/Teardown/Google+Nest+Mini+(2nd+generation)+Teardown/130974

It was at this stage I decided that I could make this a speaker, eventually deciding on putting in a Pi Zero W, where the original mini circuitry was.