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openbeacon-case

##OpenBeacon proximity tag case##

alt tag alt tag alt tag

Taking part in a study involving 70 participants, and having no available case fitting our needs for the proximity tag we'd use, we decided to design our own.

Technical details about the tag can be found on OpenBeacon.org.

Our main challenges were:

  • Maximize the compliance of hospital personals and patients taking part in our planned study. To help achieve the best possible compliance, the case should have a dedicated space to hold a sticker with the hospital logo, and should be nice-looking of course.
  • Have a tag that could be hooked to a lanyard or hooked to a safety pin.
  • The case should be relatively easy to open and close, but not too much so. Easy for battery replacement or whenever direct access to the PCB is needed, but not so easy that no tool is needed.
  • The case should be somewhat waterproof.
  • The button on the PCB should be accessible.
  • Take advantage of the full capabilities of the tag. One of the requirements was that the tag point towards the front and stay so.
  • Find the right 3D design tool. We are no 3D designers, we work on Macs and we wanted fast results, so after reviewing a few softwares, we chose 123d Design by AUTODESK. Its learning curve seemed the best of all reviewed tools, the examples looked great, it can export .STL files used by 3D printers and it's free.

We didn't need a case:

  • that could resist huge shocks
  • that could be used for years

3D-Printing

The case was printed at the Centre universitaire d'informatique, Geneva University, by a Stratasys Objet260. Thanks to Daniel Agulleiro for his great advices and help.

The printer used allows printing several materials at once, with different softness and color. All materials are polymerized together, giving absolutely great results. All parts are printed mate (as opposed to glossy).

Materials used:

  • White parts: RGD515 + RGD531 (Ivory)
  • Button rubber part: Tango Black+ xxxxx60
  • All other black parts: Tango Black+ xxxxx40

alt tag alt tag alt tag alt tag alt tag alt tag

Cases are printed in rows. Time to print is roughly proportional to the number of rows needed on the printer board times the height of the highest object (in mm) x 5. In our case, a row like this one:

alt tag

...took around 1 x 10 mm x 5 = 50 minutes to print.

Each part must then be cleaned.

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Signal attenuation

A rapid set of test measurements done at the ISI Foundation in Torino, with and without the case, seemed to show that, despite being measurable, the signal attenutation by the case would not affect the quality of the interaction measurements.

Waterproof?

The case was hold for one minute under 15 cm of water. We then opened it and found no trace of water inside. That seemed enough for our needs.