+++ /dev/null
-#+TITLE: Portable stereo speaker
-#+AUTHOR: Svjatoslav Agejenko
-#+LANGUAGE: en
-
-* (document settings) :noexport:
-** use dark style for TWBS-HTML exporter
-#+HTML_HEAD: <link href="https://bootswatch.com/3/darkly/bootstrap.min.css" rel="stylesheet">
-#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
-#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/js/bootstrap.min.js"></script>
-#+HTML_HEAD: <style type="text/css">
-#+HTML_HEAD: footer {background-color: #111 !important;}
-#+HTML_HEAD: pre {background-color: #111; color: #ccc;}
-#+HTML_HEAD: </style>
-
-* General
-+ 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.
-
-+ This design is released under Creative Commons Zero (CC0) license.
-
-+ Author:
- - Svjatoslav Agejenko
- - Homepage: https://svjatoslav.eu
- - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]
-
-+ See also:
- - [[../../index.html][Other physical projects in this repository]]
- - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]
-
-* Project description
-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:
-
-[[file:make.png]]
-
-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.
-
-[[file:make,%20side.png]]
-
-Idea for the holes on the top and smaller ones on the bottom back is
-to enable air flow for passive cooling.
-
-[[file:make,%20back.png]]
-
-Entire construction is made of parts, no larger than
-120x120x120mm. Maximum for my printer.
-
-* Battery holder
-Device is powered by 4 times AA NiMH batteries (1.2V each).
-
-[[file:battery%20holder/schematic.png]]
-
-I happened to have AA battery adapters lying around with different
-bottom hole configurations. Therefore this weird hole design:
-
-[[file:battery%20holder/battery%20holder.png]]
-
-Download:
-+ [[file:battery%20holder/battery%20holder.FCStd][FreeCAD file]]
-+ [[file:battery%20holder/battery%20holder.stl][STL file]]
-
-Result:
-[[file:battery%20holder/make.png]]
-
-Attaches to the back of the body:
-[[file:battery%20holder/mounted%20on%20the%20back.png]]
-
-* 20V up-step module
-Battery pack voltage is routed through main on/off switch on the front
-panel, and then it goes to the 20V up-step module.
-
-[[file:20V%20upstep%20module/schematic.png]]
-
-It uses ready made upstep module, but adds extra voltage filtering via
-inductor and capacitors.
-
-[[file:20V%20upstep%20module/make.png]]
-
-* Main board
-
-Voltage upstep above sits on top of main board (motherboard). It has
-uniform central bus that spans all connectors.
-
-[[file:main%20board/internal%20bus.png]]
-
-[[file:main%20board/bus%20on%20the%20bottom,%202.png]]
-
-First row of the main board is special IO terminal (for connecting
-speakers, front panel, etc..)
-
-[[file:main%20board/IO%20terminal.png]]
-
-Remaining rows are for connecting boards:
-
-[[file:main%20board/1.png]]
-
-To provide structural support, main board is attached to frame:
-
-[[file:main%20board/board%20fixator%20body.png]]
-
-Download:
-+ [[file:main%20board/board%20fixator%20body.FCStd][FreeCAD file]]
-+ [[file:main%20board/board%20fixator%20body.stl][STL file]]
-
-And boards plugged into main board are fixed at the top, using clip:
-
-[[file:main%20board/board%20fixator%20top%20clip.png]]
-
-Download:
-+ [[file:main%20board/board%20fixator%20top%20clip.FCStd][FreeCAD file]]
-+ [[file:main%20board/board%20fixator%20top%20clip.stl][STL file]]
-
-Result:
-
-[[file:main%20board/bus%20on%20the%20bottom,%201.png]]
-
-[[file:main%20board/board%20fixator.png]]
-
-* Mono audio amplifier module
-
-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.
-
-[[file:mono%20audio%20amp%20module/schematic.png]]
-
-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:
-
-[[file:mono%20audio%20amp%20module/PCB%20layout.png]]
-
-Result - front:
-
-[[file:mono%20audio%20amp%20module/assembled%20front.png]]
-
-Result - back:
-
-[[file:mono%20audio%20amp%20module/assembled%20back.png]]
-
-Here copper tape is used as improvised heatsink.
-
-* Speakers
-
-High frequency small speaker and medium frequency bigger speaker are
-combined.
-
-[[file:speakers/schematic.png]]
-
-Capacitor acts as high-pass filter on top of tiny PCB:
-
-[[file:speakers/PCB%20layout.png]]
-
-Speaker enclosure:
-
-[[file:speakers/speaker%20enclosure.png]]
-
-Download:
-+ [[file:speakers/speaker%20enclosure.FCStd][FreeCAD file]]
-+ [[file:speakers/speaker%20enclosure.stl][STL file]]
-
-Speaker enclosure cover:
-
-[[file:speakers/speaker%20enclosure%20cover.png]]
-
-Download:
-+ [[file:speakers/speaker%20enclosure%20cover.FCStd][FreeCAD file]]
-+ [[file:speakers/speaker%20enclosure%20cover.stl][STL file]]
-
-Result:
-
-[[file:speakers/make.png]]
-
-* Front panel
-
-Initial idea was really simple panel:
-+ on/off switch
-+ system power indicator
-+ stereo audio input
-
-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.
-
-[[file:front%20panel/schematic.png]]
-
-Front panel case:
-
-[[file:front%20panel/front%20panel,%20front.png]]
-
-[[file:front%20panel/front%20panel,%20back.png]]
-
-Electronics fits inside:
-
-[[file:front%20panel/front%20panel,%20back,%20make.png]]
-
-Front view:
-
-[[file:front%20panel/front%20panel,%20front,%20make.png]]
-
-And attaches to the remaining components:
-
-[[file:front%20panel/attachment.png]]
-
-
-* Extra capacitors
-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.
-
-[[file:extra%20capacitors/extra%20caps.png]]
-
-Download:
-+ [[file:extra%20capacitors/extra%20caps.FCStd][FreeCAD project]]
-+ [[file:extra%20capacitors/extra%20caps.stl][STL file]]
-
-Extra caps are mounted on top of the speaker and electrically attached
-to the main board.
-
-[[file:extra%20capacitors/make.png]]
-
-* Center box
-
-Last physical part, to attach it all together: central body.
-
-Front:
-[[file:center%20box/front.png]]
-
-Back:
-[[file:center%20box/back.png]]
-
-Download:
-+ [[file:center%20box/center%20box.FCStd][FreeCAD file]]
-+ [[file:center%20box/center%20box.stl][STL file]]
-
-
-* Conclusions / TODO
-
-These things could be done better:
-
-+ 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.
-
-+ 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.
-
-+ Screw holes are too close to the edges on the front panel.
-
-+ It would be better if screw heads were slightly buried within
- construction body.
-
-
-Overall, it was good learning experience and I was able to test
-various ideas on it. Will add cooler later :)
-
-
-Photo of initial PSU + audio amp test:
-
-[[file:initial%20test.png]]
projects / physical.git / blobdiff