Project LOUD: A Portable, Solar-Charging, Power Bank Equipped, High Decibel Bluetooth Speaker

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Andrew Overby
10 / 23 / 2017

Like most projects, it began with a vision. I have been a huge fan of Bluetooth technology and its diversity in product applications ever since the word became a household name. The implication of its designs never cease to amaze me. It had been a long time goal of mine to make one, incorporating my own ideas, but with new companies frequently adding to the competitive market of these speakers, what could I do to make mine stand out among the rest?

The first thing that popped into my head was "loud." Like most engineers, I am always a fan of ridiculous ideas, and I made it the focal point of my speaker to be the shear volume it can reach. I told myself that this speaker will be louder than any Bluetooth speaker I have ever heard before, and I took the measures to do so.

Not only did I want this speaker to be loud, but be a tool for the user. Not only could one play music to its full potential via Bluetooth, but they could also charge their phone from the battery pack inside the speaker, and if they were to run out of battery while enjoying their beautiful day outside, no problem, because the speaker would have solar charging, too.

Next on the list was research. I needed to know what was required to make this speaker as loud as possible but also perform the other tasks efficiently. First on the list was the batteries, and lithium ion batteries proved to be the best choice for this application. Learning about l-ion batteries, specifically 18650 was a great learning experience and I can see it rolling over into many future projects. Not only does the battery supply a great voltage for common electronics, but a high capacity; therefore, they last much longer than regular batteries would. For my first prototype I ordered the following parts.

  • 3.7V 20000MAH l-ion battery   (as explained above)
  • DC-DC buck converter   (to boost the voltage of the supply - the amp needed 12V potential when the battery only supplied 3.7V)
  • 150W power inverter   (in order to charge a device via USB and use AC power via outlet)
  • Lighted toggle power switch   (because it looks cool!)
  • TP4056 charging module   (for balanced charging and to prevent over-charge and over-discharge)
  • Goldwood 4 inch speakers with a 50W + 50W amplifier board (loud was the key seller on these ones)
  • Two 25W solar panels (having two wired in parallel would increase the charging rate)

After receiving the parts and eagerly wiring it all together:

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All in all, I was very proud of my first attempt at configuring everything; however, I ran into a few problems. The biggest of the problems was that the power inverter was not sending enough current through the AC outlet and whenever I plugged a USB into it the buck converter would become very hot. This proved to be a problem and I had to completely throw away the idea of the power inverter and instead go with a DC-DC step up USB converter instead. I later found out in order to use this power inverter I would have needed a power supply closer to 12V than 3.7V. It was sending too much current through the buck converter and it was not enough to power itself efficiently. After solving that problem and quickly wiring up the solar panels hassle-free, it was to the drawing board.

I wanted to go for a design I had not seen before and I thought a driver array in the shape of a cube would be the perfect route to go. The speaker was to be medium sized, for I wanted it to have an all-around application. From home theater to backyard parties, this speaker would handle the task.

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After drawing out the sketches to-scale, it was very easy to start the building process. I decided to use some salvaged wood that my dad found from a friend. It was 3/4" thick maple, a very dense wood which meant great sound resonance. The building process proved to be hard. Figuring out how to glue a cube together is not the easiest thing I have ever done, but was a great learning experience. Completing the project felt extremely rewarding, and listening to the speaker made it even more surreal. It is great to see a product you have worked long and hard for come to life, and I plan on building a second prototype in the future. More images of the building process and final speaker are shown below.

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