Baby Steps

A project log for Ultrasonic Directional Speaker v1

Producing highly directional sound from 40kHz ultrasonic transducers

Alan GreenAlan Green 01/22/2016 at 21:442 Comments

I'm constantly torn by how "finished" a product I ought to be aiming for. It's very tempting to over polish, but I'm not looking to produce a mass-market device. Instead I should focus on the requirements, then plan how to get there.

Requirements for V1

For March, I want to build a device that

  1. has two, independent channels (not really stereo, as mostly people will only hear one channel at a time).
    1. Each channel ought to have its own volume control
    2. Each channel ought to be output to its own speaker
  2. is reliable enough to support Mitchell's practice and performance sessions without needing tinkering.
  3. is easy to operate so changes can be made on-stage if required
    1. On-off switch on front panel
    2. Easy to twiddle volume knobs controls
    3. Some kind visual indication of current performance, such as a VU meter.two or maybe three devices that work reasonably reliably.
  4. Safely packaged to avoid electrical and physical hazards.

Future Versions

Things I don't need to do

  1. MIDI, Internal Synthesizer.
  2. SDCard for sound files.
  3. Touch screen.

The Plan

Here's the outline of how I want to get from where I am to V1

  1. Prototype single channel on a breadboard
    1. Use bench power supply and power over USB
    2. Build input circuitry, with amplification and voltage protection for the Arduino.
    3. Build single channel output circuitry
      1. incorporate opto isolators
      2. test a 4x4 transducer array, see if an inductor would help
      3. build 5x10 or 7x7 array
  2. Figure out mains power supply
    1. Carefully consider safety aspects
    2. Build it, for real. It should supply 48v, 12v and 5v power.
  3. Build dual channel input
    1. lay out circuitry in diagram first
    2. build on perfboard
  4. Build output channel
    1. lay out circuitry in diagram
    2. build on perfboard
  5. Build transducer arrays.
    1. 2x 100 or 200 transducer arrays
    2. test and iterate
  6. Build an enclosure.
  7. Stand back and admire the work.


ziggurat29 wrote 01/23/2016 at 23:10 point

You're smart to resist being seduced into 'over-polishing' as you say (or 'gold-gilding' as sometimes others say) at an early phase in the project. The stuff you are doing is really exciting.  If you make the ultrasonic transducer array work predictably and reliably, then all the fiddly bits of UI and whatnot will be child's play to resolve as a separate activity from creating the core technology. You might even be able to enlist other folks interested in your tech to do that part for you.

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Alan Green wrote 01/25/2016 at 21:33 point

Yes, it's really easy to get carried away thinking about how to make something look "like a bought one" rather than actually just making something that works.

Thanks for your encouragement.

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