A week ago I finished my audio cooler. Although I was happy with the result improvements could be made (as is always the case). Most important I didn’t particularly like the console on the side of the coolers lid. This was a 3d printed part of PLA that I glued to cooler with a superglue. This was far from ideal because of the space left between the printed console and the cooler . Another improvement could be made by the way that the speaker was fitted to the lid of the cooler. The speaker was directly attached to cooler with four screws again leaving some space between the two. I already had some FilaFlex filament but hadn’t used it yet. Because of the elastic and flexible properties of Filaflex I figured that I could both fix the issues with the console and the speaker.
Left the cooler with improved speaker and console and right “old cooler” with printed part of PLA filament.
Yes, the Raspberry Pi with MPD is a nice addition to the cooler but it has it's drawbacks such as power consumption and added occupied space.
Introduction
In my previous blog post I finished my audio cooler. It’s a small cooler with a tiny audio system that nevertheless sounds good. The only way to control the audio is through a wired connection. It would be a nice addition to have some kind of remote control either by WiFi or Bluetooth. While testing the cooler I’ve got the idea to connect a Raspberry Pi A+, that was still unused, to the cooler and stream audio over WiFi to the Pi. This could be useful for a garden party or BBQ where WiFi is available and I don’t want to attach the smartphone to the cooler. In this blog post I’ll share my experience with installation and operating the software needed for this project on the Pi.
Raspberry Pi A+ (in it’s Pimoroni Pibow case) connected with the headphone jack to the cooler. The Pi has a small Edimax Wifi adapter.
Installing music software on the Raspberry Pi
Since I run the Raspberry Pi headless I use SSH login to the Pi. SSH is available for most operating systems with the notable exception of Windows. I already had Raspbian installed on the Pi so first I updated the OS.
A couple of weeks ago I started to make a tiny audio system for our cooler. In my previous blogpost I described all the audio components that I chose for this project. I wanted the components to be small since I didn’t want to waste too much space in the cooler. With the audio components in hand I could design other parts for the audio system. I needed an enclosure for most of the audio components and a simple console to operate the audio. The parts were 3d printed with my Hephestos 2.
The complete audio system in the lid of the cooler. Most components are placed in the 3d printed enclosure.
For pick nicks we use a small cooler and with the upcoming spring and summer it seems like a great idea to add an audio system to it. Most DIY coolers with audio that I found on the internet are huge. Not only do they have large speakers and amplifiers but they also have a huge lead battery hardly leaving any space for the pick nick gear. I want a tiny, one speaker system that sounds nice but is lightweight and leaves plenty of room for the other stuff. I also wanted it nicely integrated in the cooler without too many wires. I therefore started to design and build one.
Choosing the audio components
I started this project by choosing a suitable battery. As stated above lead batteries are relatively large due to their low energy density. Lithium polymer batteries on the other hand have large energy density, four to five times higher than lead according to this source. Prices of polymer batteries are also very reasonable nowadays.
Lead-acid battery (left) and polymer battery (right) side by side on the small cooler. The much bigger and heavier lead-acid battery has a capacity of 5000mAh (6V) while the lithium polymer battery has 1200mAh (3,7V). The lithium polymer with it’s four to five times larger energy density is therefore perfect for my small audio system.
Next I chose the amplifier. I was looking for a small one with just enough power to provide a good sound with a proper speaker. There is plenty of choice but I chose the Kemo 3,5W (M031N) since it’s small but also humidity and shake proof. It also comes in a nice package and has a broad operating voltage range from 4.5-12V/DC.
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