misc/portable stereo active speaker/index.org

   1 #+TITLE: Portable stereo speaker
   2 #+AUTHOR: Svjatoslav Agejenko
   3 #+LANGUAGE: en
   4
   5 * (document settings) :noexport:
   6 ** use dark style for TWBS-HTML exporter
   7 #+HTML_HEAD: <link href="https://bootswatch.com/3/darkly/bootstrap.min.css" rel="stylesheet">
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  13 #+HTML_HEAD: </style>
  14
  15 * General
  16 + DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
  17   COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
  18   DESIGNS AT YOUR OWN RISK.
  19
  20 + This design is released under Creative Commons Zero (CC0) license.
  21
  22 + Author:
  23   - Svjatoslav Agejenko
  24   - Homepage: https://svjatoslav.eu
  25   - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]
  26
  27 + See also:
  28   - [[../../index.html][Other physical projects in this repository]]
  29   - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]
  30
  31 * Project description
  32 I had pair of good compact stereo speakers lying uselessly around as
  33 well as secondhand TDA2030 Chinese knockoff audio amplifier chips.
  34 Also I wanted to test modular construction approach: motherboard with
  35 shared bus and functionality realized via pluggable modules. So I
  36 built stereo speaker:
  37
  38 [[file:make.png]]
  39
  40 Indicator on the front panel shows available power within the
  41 system. Ideally it should be at the maximum. It drops when batteries
  42 run empty or when consumed power (too loud music) is greater than
  43 onboard power supply or batteries can handle. It has on/off switch and
  44 stereo audio input. Audio input impedance is about 100 ohms.
  45
  46 [[file:make,%20side.png]]
  47
  48 Idea for the holes on the top and smaller ones on the bottom back is
  49 to enable air flow for passive cooling.
  50
  51 [[file:make,%20back.png]]
  52
  53 Entire construction is made of parts, no larger than
  54 120x120x120mm. Maximum for my printer.
  55
  56 * Battery holder
  57 Device is powered by 4 times AA NiMH batteries (1.2V each).
  58
  59 [[file:battery%20holder/schematic.png]]
  60
  61 I happened to have AA battery adapters lying around with different
  62 bottom hole configurations. Therefore this weird hole design:
  63
  64 [[file:battery%20holder/battery%20holder.png]]
  65
  66 Download:
  67 + [[file:battery%20holder/battery%20holder.FCStd][FreeCAD file]]
  68 + [[file:battery%20holder/battery%20holder.stl][STL file]]
  69
  70 Result:
  71 [[file:battery%20holder/make.png]]
  72
  73 Attaches to the back of the body:
  74 [[file:battery%20holder/mounted%20on%20the%20back.png]]
  75
  76 * 20V up-step module
  77 Battery pack voltage is routed through main on/off switch on the front
  78 panel, and then it goes to the 20V up-step module.
  79
  80 [[file:20V%20upstep%20module/schematic.png]]
  81
  82 It uses ready made upstep module, but adds extra voltage filtering via
  83 inductor and capacitors.
  84
  85 [[file:20V%20upstep%20module/make.png]]
  86
  87 * Main board
  88
  89 Voltage upstep above sits on top of main board (motherboard). It has
  90 uniform central bus that spans all connectors.
  91
  92 [[file:main%20board/internal%20bus.png]]
  93
  94 [[file:main%20board/bus%20on%20the%20bottom,%202.png]]
  95
  96 First row of the main board is special IO terminal (for connecting
  97 speakers, front panel, etc..)
  98
  99 [[file:main%20board/IO%20terminal.png]]
 100
 101 Remaining rows are for connecting boards:
 102
 103 [[file:main%20board/1.png]]
 104
 105 To provide structural support, main board is attached to frame:
 106
 107 [[file:main%20board/board%20fixator%20body.png]]
 108
 109 Download:
 110 + [[file:main%20board/board%20fixator%20body.FCStd][FreeCAD file]]
 111 + [[file:main%20board/board%20fixator%20body.stl][STL file]]
 112
 113 And boards plugged into main board are fixed at the top, using clip:
 114
 115 [[file:main%20board/board%20fixator%20top%20clip.png]]
 116
 117 Download:
 118 + [[file:main%20board/board%20fixator%20top%20clip.FCStd][FreeCAD file]]
 119 + [[file:main%20board/board%20fixator%20top%20clip.stl][STL file]]
 120
 121 Result:
 122
 123 [[file:main%20board/bus%20on%20the%20bottom,%201.png]]
 124
 125 [[file:main%20board/board%20fixator.png]]
 126
 127 * Mono audio amplifier module
 128
 129 Design uses scavenged secondhand Chinese TDA2030 audio amp
 130 clones. Each chip is mono audio amplifier. Therefore 2 almost
 131 identical audio amp modules had to be built, one for left speaker, one
 132 for right.
 133
 134 [[file:mono%20audio%20amp%20module/schematic.png]]
 135
 136 I like to build on top of prototype PCBs. Gives results much faster
 137 for one-off projects. Before soldering, I solve component layout on
 138 paper:
 139
 140 [[file:mono%20audio%20amp%20module/PCB%20layout.png]]
 141
 142 Result - front:
 143
 144 [[file:mono%20audio%20amp%20module/assembled%20front.png]]
 145
 146 Result - back:
 147
 148 [[file:mono%20audio%20amp%20module/assembled%20back.png]]
 149
 150 Here copper tape is used as improvised heatsink.
 151
 152 * Speakers
 153
 154 High frequency small speaker and medium frequency bigger speaker are
 155 combined.
 156
 157 [[file:speakers/schematic.png]]
 158
 159 Capacitor acts as high-pass filter on top of tiny PCB:
 160
 161 [[file:speakers/PCB%20layout.png]]
 162
 163 Speaker enclosure:
 164
 165 [[file:speakers/speaker%20enclosure.png]]
 166
 167 Download:
 168 + [[file:speakers/speaker%20enclosure.FCStd][FreeCAD file]]
 169 + [[file:speakers/speaker%20enclosure.stl][STL file]]
 170
 171 Speaker enclosure cover:
 172
 173 [[file:speakers/speaker%20enclosure%20cover.png]]
 174
 175 Download:
 176 + [[file:speakers/speaker%20enclosure%20cover.FCStd][FreeCAD file]]
 177 + [[file:speakers/speaker%20enclosure%20cover.stl][STL file]]
 178
 179 Result:
 180
 181 [[file:speakers/make.png]]
 182
 183 * Front panel
 184
 185 Initial idea was really simple panel:
 186 + on/off switch
 187 + system power indicator
 188 + stereo audio input
 189
 190 But, since I'm using "agile" approach, during load-testing, it become
 191 clear that active fan based cooling would be nice (when playing loud
 192 music). I found tiny cooler fan that needs 5 volts to operate. Also I
 193 need to power backlight for power indicator. For both of these cases,
 194 I decided to add another voltage up-step module (target voltage output
 195 set to 6V). This time directly on the front panel.
 196
 197 [[file:front%20panel/schematic.png]]
 198
 199 Front panel case:
 200
 201 [[file:front%20panel/front%20panel,%20front.png]]
 202
 203 [[file:front%20panel/front%20panel,%20back.png]]
 204
 205 Electronics fits inside:
 206
 207 [[file:front%20panel/front%20panel,%20back,%20make.png]]
 208
 209 Front view:
 210
 211 [[file:front%20panel/front%20panel,%20front,%20make.png]]
 212
 213 And attaches to the remaining components:
 214
 215 [[file:front%20panel/attachment.png]]
 216
 217 * Extra capacitors
 218 Another thing that become clear during load-testing: output
 219 power/volume can be further enhanced by adding high power capacitors
 220 to even out load on primary 20V up-step module.
 221
 222 [[file:extra%20capacitors/extra%20caps.png]]
 223
 224 Download:
 225 + [[file:extra%20capacitors/extra%20caps.FCStd][FreeCAD project]]
 226 + [[file:extra%20capacitors/extra%20caps.stl][STL file]]
 227
 228 Extra caps are mounted on top of the speaker and electrically attached
 229 to the main board.
 230
 231 [[file:extra%20capacitors/make.png]]
 232
 233 * Center box
 234
 235 Last physical part, to attach it all together: central body.
 236
 237 Front:
 238 [[file:center%20box/front.png]]
 239
 240 Back:
 241 [[file:center%20box/back.png]]
 242
 243 Download:
 244 + [[file:center%20box/center%20box.FCStd][FreeCAD file]]
 245 + [[file:center%20box/center%20box.stl][STL file]]
 246
 247 * Conclusions / TODO
 248 Photo of initial PSU + audio amp test:
 249 [[file:initial%20test.png]]
 250
 251
 252 Improvement ideas:
 253
 254 + Instead of using undersized heatsinks on the audio amplifiers and
 255   need for active cooling as a consequence, it would be better to try
 256   to mount audio amplifier chip on top of speaker metallic body. It
 257   would provide plenty of cooling and reduces power losses within
 258   cable, since amplifier would be as close to the speaker as possible.
 259
 260 + Add possibility to power device from USB socket in addition to
 261   batteries.
 262
 263 + Front panel:
 264   + Use digital voltage indicator to gauge remaining battery power.
 265
 266   + Add possibility to have multiple inputs.
 267
 268   + It would be better if screw heads were slightly buried within
 269     construction body.
 270
 271   + Screw holes are too close to the edges on the front panel.