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-<div class="row"><div class="col-md-9"><h1 class="title">Portable stereo speaker</h1>
-
-<div id="outline-container-sec-1" class="outline-2">
-<h2 id="sec-1"><span class="section-number-2">1</span> General</h2>
-<div class="outline-text-2" id="text-1">
-<ul class="org-ul">
-<li>DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
-COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
-DESIGNS AT YOUR OWN RISK.
-</li>
-
-<li>This design is released under Creative Commons Zero (CC0) license.
-</li>
-
-<li>Author:
-<ul class="org-ul">
-<li>Svjatoslav Agejenko
-</li>
-<li>Homepage: <a href="https://svjatoslav.eu">https://svjatoslav.eu</a>
-</li>
-<li>Email: <a href="mailto://svjatoslav@svjatoslav.eu">svjatoslav@svjatoslav.eu</a>
-</li>
-</ul>
-</li>
-
-<li>See also:
-<ul class="org-ul">
-<li><a href="../../index.html">Other physical projects in this repository</a>
-</li>
-<li><a href="https://www.svjatoslav.eu/projects/">Other projects hosted at svjatoslav.eu</a>
-</li>
-</ul>
-</li>
-</ul>
-</div>
-</div>
-
-<div id="outline-container-sec-2" class="outline-2">
-<h2 id="sec-2"><span class="section-number-2">2</span> Project description</h2>
-<div class="outline-text-2" id="text-2">
-<p>
-I had pair of good compact stereo speakers lying uselessly around as
-well as secondhand TDA2030 Chinese knockoff audio amplifier chips.
-Also I wanted to test modular construction approach: motherboard with
-shared bus and functionality realized via pluggable modules. So I
-built stereo speaker:
-</p>
-
-
-<figure>
-<p><img src="make.png" class="img-responsive" alt="make.png">
-</p>
-</figure>
-
-<p>
-Indicator on the front panel shows available power within the
-system. Ideally it should be at the maximum. It drops when batteries
-run empty or when consumed power (too loud music) is greater than
-onboard power supply or batteries can handle. It has on/off switch and
-stereo audio input. Audio input impedance is about 100 ohms.
-</p>
-
-
-<figure>
-<p><img src="make,%20side.png" class="img-responsive" alt="make,%20side.png">
-</p>
-</figure>
-
-<p>
-Idea for the holes on the top and smaller ones on the bottom back is
-to enable air flow for passive cooling.
-</p>
-
-
-<figure>
-<p><img src="make,%20back.png" class="img-responsive" alt="make,%20back.png">
-</p>
-</figure>
-
-<p>
-Entire construction is made of parts, no larger than
-120x120x120mm. Maximum for my printer.
-</p>
-</div>
-</div>
-
-<div id="outline-container-sec-3" class="outline-2">
-<h2 id="sec-3"><span class="section-number-2">3</span> Battery holder</h2>
-<div class="outline-text-2" id="text-3">
-<p>
-Device is powered by 4 times AA NiMH batteries (1.2V each).
-</p>
-
-
-<figure>
-<p><img src="battery%20holder/schematic.png" class="img-responsive" alt="schematic.png">
-</p>
-</figure>
-
-<p>
-I happened to have AA battery adapters lying around with different
-bottom hole configurations. Therefore this weird hole design:
-</p>
-
-
-<figure>
-<p><img src="battery%20holder/battery%20holder.png" class="img-responsive" alt="battery%20holder.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="battery%20holder/battery%20holder.FCStd">FreeCAD file</a>
-</li>
-<li><a href="battery%20holder/battery%20holder.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-Result:
-<img src="battery%20holder/make.png" class="img-responsive" alt="make.png">
-</p>
-
-<p>
-Attaches to the back of the body:
-<img src="battery%20holder/mounted%20on%20the%20back.png" class="img-responsive" alt="mounted%20on%20the%20back.png">
-</p>
-</div>
-</div>
-
-<div id="outline-container-sec-4" class="outline-2">
-<h2 id="sec-4"><span class="section-number-2">4</span> 20V up-step module</h2>
-<div class="outline-text-2" id="text-4">
-<p>
-Battery pack voltage is routed through main on/off switch on the front
-panel, and then it goes to the 20V up-step module.
-</p>
-
-
-<figure>
-<p><img src="20V%20upstep%20module/schematic.png" class="img-responsive" alt="schematic.png">
-</p>
-</figure>
-
-<p>
-It uses ready made upstep module, but adds extra voltage filtering via
-inductor and capacitors.
-</p>
-
-
-<figure>
-<p><img src="20V%20upstep%20module/make.png" class="img-responsive" alt="make.png">
-</p>
-</figure>
-</div>
-</div>
-
-<div id="outline-container-sec-5" class="outline-2">
-<h2 id="sec-5"><span class="section-number-2">5</span> Main board</h2>
-<div class="outline-text-2" id="text-5">
-<p>
-Voltage upstep above sits on top of main board (motherboard). It has
-uniform central bus that spans all connectors.
-</p>
-
-
-<figure>
-<p><img src="main%20board/internal%20bus.png" class="img-responsive" alt="internal%20bus.png">
-</p>
-</figure>
-
-
-<figure>
-<p><img src="main%20board/bus%20on%20the%20bottom,%202.png" class="img-responsive" alt="bus%20on%20the%20bottom,%202.png">
-</p>
-</figure>
-
-<p>
-First row of the main board is special IO terminal (for connecting
-speakers, front panel, etc..)
-</p>
-
-
-<figure>
-<p><img src="main%20board/IO%20terminal.png" class="img-responsive" alt="IO%20terminal.png">
-</p>
-</figure>
-
-<p>
-Remaining rows are for connecting boards:
-</p>
-
-
-<figure>
-<p><img src="main%20board/1.png" class="img-responsive" alt="1.png">
-</p>
-</figure>
-
-<p>
-To provide structural support, main board is attached to frame:
-</p>
-
-
-<figure>
-<p><img src="main%20board/board%20fixator%20body.png" class="img-responsive" alt="board%20fixator%20body.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="main%20board/board%20fixator%20body.FCStd">FreeCAD file</a>
-</li>
-<li><a href="main%20board/board%20fixator%20body.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-And boards plugged into main board are fixed at the top, using clip:
-</p>
-
-
-<figure>
-<p><img src="main%20board/board%20fixator%20top%20clip.png" class="img-responsive" alt="board%20fixator%20top%20clip.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="main%20board/board%20fixator%20top%20clip.FCStd">FreeCAD file</a>
-</li>
-<li><a href="main%20board/board%20fixator%20top%20clip.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-Result:
-</p>
-
-
-<figure>
-<p><img src="main%20board/bus%20on%20the%20bottom,%201.png" class="img-responsive" alt="bus%20on%20the%20bottom,%201.png">
-</p>
-</figure>
-
-
-<figure>
-<p><img src="main%20board/board%20fixator.png" class="img-responsive" alt="board%20fixator.png">
-</p>
-</figure>
-</div>
-</div>
-
-<div id="outline-container-sec-6" class="outline-2">
-<h2 id="sec-6"><span class="section-number-2">6</span> Mono audio amplifier module</h2>
-<div class="outline-text-2" id="text-6">
-<p>
-Design uses scavenged secondhand Chinese TDA2030 audio amp
-clones. Each chip is mono audio amplifier. Therefore 2 almost
-identical audio amp modules had to be built, one for left speaker, one
-for right.
-</p>
-
-
-<figure>
-<p><img src="mono%20audio%20amp%20module/schematic.png" class="img-responsive" alt="schematic.png">
-</p>
-</figure>
-
-<p>
-I like to build on top of prototype PCBs. Gives results much faster
-for one-off projects. Before soldering, I solve component layout on
-paper:
-</p>
-
-
-<figure>
-<p><img src="mono%20audio%20amp%20module/PCB%20layout.png" class="img-responsive" alt="PCB%20layout.png">
-</p>
-</figure>
-
-<p>
-Result - front:
-</p>
-
-
-<figure>
-<p><img src="mono%20audio%20amp%20module/assembled%20front.png" class="img-responsive" alt="assembled%20front.png">
-</p>
-</figure>
-
-<p>
-Result - back:
-</p>
-
-
-<figure>
-<p><img src="mono%20audio%20amp%20module/assembled%20back.png" class="img-responsive" alt="assembled%20back.png">
-</p>
-</figure>
-
-<p>
-Here copper tape is used as improvised heatsink.
-</p>
-</div>
-</div>
-
-<div id="outline-container-sec-7" class="outline-2">
-<h2 id="sec-7"><span class="section-number-2">7</span> Speakers</h2>
-<div class="outline-text-2" id="text-7">
-<p>
-High frequency small speaker and medium frequency bigger speaker are
-combined.
-</p>
-
-
-<figure>
-<p><img src="speakers/schematic.png" class="img-responsive" alt="schematic.png">
-</p>
-</figure>
-
-<p>
-Capacitor acts as high-pass filter on top of tiny PCB:
-</p>
-
-
-<figure>
-<p><img src="speakers/PCB%20layout.png" class="img-responsive" alt="PCB%20layout.png">
-</p>
-</figure>
-
-<p>
-Speaker enclosure:
-</p>
-
-
-<figure>
-<p><img src="speakers/speaker%20enclosure.png" class="img-responsive" alt="speaker%20enclosure.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="speakers/speaker%20enclosure.FCStd">FreeCAD file</a>
-</li>
-<li><a href="speakers/speaker%20enclosure.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-Speaker enclosure cover:
-</p>
-
-
-<figure>
-<p><img src="speakers/speaker%20enclosure%20cover.png" class="img-responsive" alt="speaker%20enclosure%20cover.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="speakers/speaker%20enclosure%20cover.FCStd">FreeCAD file</a>
-</li>
-<li><a href="speakers/speaker%20enclosure%20cover.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-Result:
-</p>
-
-
-<figure>
-<p><img src="speakers/make.png" class="img-responsive" alt="make.png">
-</p>
-</figure>
-</div>
-</div>
-
-<div id="outline-container-sec-8" class="outline-2">
-<h2 id="sec-8"><span class="section-number-2">8</span> Front panel</h2>
-<div class="outline-text-2" id="text-8">
-<p>
-Initial idea was really simple panel:
-</p>
-<ul class="org-ul">
-<li>on/off switch
-</li>
-<li>system power indicator
-</li>
-<li>stereo audio input
-</li>
-</ul>
-
-<p>
-But, since I'm using "agile" approach, during load-testing, it become
-clear that active fan based cooling would be nice (when playing loud
-music). I found tiny cooler fan that needs 5 volts to operate. Also I
-need to power backlight for power indicator. For both of these cases,
-I decided to add another voltage up-step module (target voltage output
-set to 6V). This time directly on the front panel.
-</p>
-
-
-<figure>
-<p><img src="front%20panel/schematic.png" class="img-responsive" alt="schematic.png">
-</p>
-</figure>
-
-<p>
-Front panel case:
-</p>
-
-
-<figure>
-<p><img src="front%20panel/front%20panel,%20front.png" class="img-responsive" alt="front%20panel,%20front.png">
-</p>
-</figure>
-
-
-<figure>
-<p><img src="front%20panel/front%20panel,%20back.png" class="img-responsive" alt="front%20panel,%20back.png">
-</p>
-</figure>
-
-<p>
-Electronics fits inside:
-</p>
-
-
-<figure>
-<p><img src="front%20panel/front%20panel,%20back,%20make.png" class="img-responsive" alt="front%20panel,%20back,%20make.png">
-</p>
-</figure>
-
-<p>
-Front view:
-</p>
-
-
-<figure>
-<p><img src="front%20panel/front%20panel,%20front,%20make.png" class="img-responsive" alt="front%20panel,%20front,%20make.png">
-</p>
-</figure>
-
-<p>
-And attaches to the remaining components:
-</p>
-
-
-<figure>
-<p><img src="front%20panel/attachment.png" class="img-responsive" alt="attachment.png">
-</p>
-</figure>
-</div>
-</div>
-
-
-<div id="outline-container-sec-9" class="outline-2">
-<h2 id="sec-9"><span class="section-number-2">9</span> Extra capacitors</h2>
-<div class="outline-text-2" id="text-9">
-<p>
-Another thing that become clear during load-testing: output
-power/volume can be further enhanced by adding high power capacitors
-to even out load on primary 20V up-step module.
-</p>
-
-
-<figure>
-<p><img src="extra%20capacitors/extra%20caps.png" class="img-responsive" alt="extra%20caps.png">
-</p>
-</figure>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="extra%20capacitors/extra%20caps.FCStd">FreeCAD project</a>
-</li>
-<li><a href="extra%20capacitors/extra%20caps.stl">STL file</a>
-</li>
-</ul>
-
-<p>
-Extra caps are mounted on top of the speaker and electrically attached
-to the main board.
-</p>
-
-
-<figure>
-<p><img src="extra%20capacitors/make.png" class="img-responsive" alt="make.png">
-</p>
-</figure>
-</div>
-</div>
-
-<div id="outline-container-sec-10" class="outline-2">
-<h2 id="sec-10"><span class="section-number-2">10</span> Center box</h2>
-<div class="outline-text-2" id="text-10">
-<p>
-Last physical part, to attach it all together: central body.
-</p>
-
-<p>
-Front:
-<img src="center%20box/front.png" class="img-responsive" alt="front.png">
-</p>
-
-<p>
-Back:
-<img src="center%20box/back.png" class="img-responsive" alt="back.png">
-</p>
-
-<p>
-Download:
-</p>
-<ul class="org-ul">
-<li><a href="center%20box/center%20box.FCStd">FreeCAD file</a>
-</li>
-<li><a href="center%20box/center%20box.stl">STL file</a>
-</li>
-</ul>
-</div>
-</div>
-
-
-<div id="outline-container-sec-11" class="outline-2">
-<h2 id="sec-11"><span class="section-number-2">11</span> Conclusions / TODO</h2>
-<div class="outline-text-2" id="text-11">
-<p>
-These things could be done better:
-</p>
-
-<ul class="org-ul">
-<li>Instead of using undersized heatsinks on the audio amplifiers and
-need for active cooling as a consequence, it would be better to try
-to mount audio amplifier chip on top of speaker metallic body. It
-would provide plenty of cooling and reduces power losses within
-cable, since amplifier would be as close to the speaker as possible.
-</li>
-
-<li>I used agile design. That is, implemented functionality ad-hoc. If I
-had done design in advance, then I could have had smarter connector
-layout between main board and front panel. That is: Instead of
-multiple smaller cables, one wide (multi connector) cable.
-</li>
-
-<li>Screw holes are too close to the edges on the front panel.
-</li>
-
-<li>It would be better if screw heads were slightly buried within
-construction body.
-</li>
-</ul>
-
-
-<p>
-Overall, it was good learning experience and I was able to test
-various ideas on it. Will add cooler later :)
-</p>
-
-
-<p>
-Photo of initial PSU + audio amp test:
-</p>
-
-
-<figure>
-<p><img src="initial%20test.png" class="img-responsive" alt="initial%20test.png">
-</p>
-</figure>
-</div>
-</div>
-</div><div class="col-md-3"><nav id="table-of-contents">
-<div id="text-table-of-contents" class="bs-docs-sidebar">
-<ul class="nav">
-<li><a href="#sec-1">1. General</a></li>
-<li><a href="#sec-2">2. Project description</a></li>
-<li><a href="#sec-3">3. Battery holder</a></li>
-<li><a href="#sec-4">4. 20V up-step module</a></li>
-<li><a href="#sec-5">5. Main board</a></li>
-<li><a href="#sec-6">6. Mono audio amplifier module</a></li>
-<li><a href="#sec-7">7. Speakers</a></li>
-<li><a href="#sec-8">8. Front panel</a></li>
-<li><a href="#sec-9">9. Extra capacitors</a></li>
-<li><a href="#sec-10">10. Center box</a></li>
-<li><a href="#sec-11">11. Conclusions / TODO</a></li>
-</ul>
-</div>
-</nav>
-</div></div></div>
-<footer id="postamble" class="">
-<div><p class="author">Author: Svjatoslav Agejenko</p>
-<p class="date">Created: 2020-04-12 P 23:58</p>
-<p class="creator"><a href="http://www.gnu.org/software/emacs/">Emacs</a> 26.1 (<a href="http://orgmode.org">Org-mode</a> 9.1.9)</p>
-</div>
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-</body>
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projects / physical.git / blobdiff