X-Git-Url: http://www2.svjatoslav.eu/gitweb/?p=physical.git;a=blobdiff_plain;f=misc%2FPortable%20stereo%20active%20speaker%2Findex.org;fp=misc%2FPortable%20stereo%20active%20speaker%2Findex.org;h=e85fa1fa350fa37a35560c5a3ed30c32ac0b1565;hp=0000000000000000000000000000000000000000;hb=19af345819ef415d6685de55eb218367baa47b33;hpb=365f953bb4a379fb74f7ec49244484f75362c684 diff --git a/misc/Portable stereo active speaker/index.org b/misc/Portable stereo active speaker/index.org new file mode 100644 index 0000000..e85fa1f --- /dev/null +++ b/misc/Portable stereo active speaker/index.org @@ -0,0 +1,276 @@ +#+TITLE: Portable stereo speaker +#+AUTHOR: Svjatoslav Agejenko +#+LANGUAGE: en + +* (document settings) :noexport: +** use dark style for TWBS-HTML exporter +#+HTML_HEAD: +#+HTML_HEAD: +#+HTML_HEAD: +#+HTML_HEAD: + +* 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]]