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The following is my entry to Pinshape's Mechanical Design Contest.
My design is of a service bell. This bell features a conventional mechanical ringer mechanism but with a catch; no annoying 'DING!'. Instead, the power of tomorrow is harnessed to provide silent, wireless interactivity. Okay, maybe not the power of tomorrow but the bell does make use of an Adafruit Huzzah Feather board to send service requests and replies via the web [io.adafruit.com]. The board and rechargeable battery are hidden in the base with an outlet for a micro USB charging cable. A service request is sent when the striker hits a small lever switch inside of the bell that is connected to the board. A Neopixel ring is embedded in the top of the base that lights up the inside of the bell with 12 RGB LEDs. When service is needed, the bell turns red. When acknowledged via phone the bell goes back to green or whatever color is appropriate.
The idea is inspired by the need for a silent, affordable way to call for service or let someone know you're here. Like in a therapists reception area. The idea came from my wife and the inspiration to try and make it came from this contest. I don't know who originally invented the service bell mechanism, I just looked at a dollar-store bell for reference.I'm including a few pictures and two short videos to go along with my descriptions...
This is the cool part and the non-electrical mechanical part of the design. This little guy rest with a strike-plate under the pin, lifting it up. When the pin is pushed down, the ringer swings and its hammer end strikes the inside of the bell (lever switch in this case). Then gravity takes over and pulls the hammer back down, thus pushing the pin back up. No springs needed! View the quick video for a cut-away view of the ringer in action.
To assemble the Ringer, print it out then heat the hammer 'fins' and bend them backwards. Let cool to restore rigidity.
The bell is a 3mm thick white polymer shell. I originally tried to print this with my own printer with no luck. I decided to try sending away for an SLA print of my design. The print and material is awesome and diffuses the LED lights beautifully. It's very rigid but not too brittle. I did shatter one when trying to squeeze it back to being round (packing and shipping left the bell slightly oval shaped.
The base is printed in Carbon Fiber PLA. It has room for an Adafruit feather board with header. There is an offset to keep the board to the side in order to allow for the battery to also sit flat. The base takes me almost 9 hours to print at .1 mm at 40 m/s.
The Bracket has an M8 threaded hole at the top that allows the bell to be screwed in place. The support holes for the ringer/striker are offset so that the strike-plate rest directly under the cener hole (where the pin falls). My printer doesn't have the tolerance, so I had to super-glue the bracket onto the base. A bit of sanding and you'd never know.
The pin printed a little thick and a bit too long. I fine tuned it by sanding it and trimming to length.
The fiducial is purely cosmetic and screws onto the top.
This lid wiggles onto the top of the base and allows a 12-pixel neopixel ring to sit within it. There are holes to allow connection wire to pass from underneath. I might glue the lid in place when all is said and done. In hind-sight, the lid is nice but can imped the stiker. The lid now rest just inside the base.
Battery: 500mA li-po
Switch: The smallest I could find off-the-shelf
MCU and Wifi: Adafruit Huzzah Feather (Got from Adabox 003)
Code: I'm happy to share. Mostly just an amalgamation of adafruit.io tutorials Cloud: io.adafruit.com
To Do in the Future:
Incorporate Wireless Charging? Create alternate way to reply (without phone), maybe hit ringer a few times in a row.