Gravicase

Project Overview

Computers, tablets, smartphones all of these objects cost hundreds of dollars. We buy them for their sleek designs and fluid screens and buttons. Then in order to protect them, we seal them away in big bulky cases, trapping our smooth phones or computers behind sturdy yet cumbersome plastic while we cover the vibrant screens with a dull, always cloudy screen protector. And the worst part of all? We still hold our breath when we drop our hundred dollar investments until we see the screen unharmed. There is no confidence in the ability of current conventional cases to protect our electronics.

A prototype design for Gravicase

Our group has proposed Gravicase as a proof of concept solution to this problem. With Gravicase, we hope to create a device which can be attached to the back of one's personal electronics. Gravicase aims to maximize protection while minimizing the negative impact of one's experience with their electronics. Gravicase protects your precious possessions by deploying an airbag that envelopes your phone, computer, tablet, etc. and protects it from fall damage. While we do not have a quantifiable value for the effectiveness of Gravicase vs. conventional electronics protection, the effect of adding airbags in cars have improved survival rates in head on collisions by 30% (section 4 of link), even as the strength of the other materials in cars decreases (changes from heavier stronger steel to lighter aluminum). Similarly side airbags have increased survival rates in side collisions by 50% (section 4 of link). Gravicase adopts a similar approach. By surrounding your electronics with an airbag on all sides, Gravicase protects from blunt force drop damage at any angle.

Gravicase is an Arduino controlled device which attaches to your personal electronic devices and, when dropped, deploys a CO2 powered airbag that envelops and protects whatever it is attached to. The Arduino uses an accelerometer to sense when it is being dropped, as well as if it tumbling, so that it can accurately and safely differentiate a fall compared to other movements one would take (aka walking, running, jumping, etc). This dual safety measure allows for Gravicase to avoid activating in your bag or pocket and be ready when it counts! We will detail how we accomplished this as well as more in depth measures we took for safety and execution in the "Objective" and "Designs and Solutions" sections of our wiki.

Link to GraviCase Log: here

Link to the slides from our class presentation on Gravicase from 9.29.2017: here

Team Members

• Matt Rocco
• Michael Morgan
• Andrew O'Sullivan (TA)

Objectives

Our project objectives are as follows:

• 1) Designing a device which allows us to lay out all of the components of our device
  • Houses the airbag in the middle so that it is centered on the device for even protection
  • Trying to minimize our layout to be as discreet and form fitting as possible
• 2) Writing Arduino code which is both effective as well as safe
  • Preventing our design from popping in your pocket or bag or any time other than when it is falling
  • Developing durable and robust code which can handle constant data monitoring, and quickly analyze when it is being dropped from the real world information it receives
• 3) Creating an airtight system
  • Preventing CO2 from escaping so that it is pressurized and ready to go when the device is dropped
    • Ensuring that all of the CO2 cartridge's volume ends up in the airbag to maximize its efficiency
• 4) Designing an airbag which can absorb a blunt force impact as well as be easily deflated in order to be reused
  • Sewing a shape that protects all parts of the device when inflated
  • Finding a material that can easily be worked with as well as fits the design needs we desire (durability, as well as reusability)
  • Protects all parts of the device (ex. phone screen as well as back and sides)
  • Maintaining a compact and foldable form but being able to achieve the functions described above
• 5) The ability to pop the canister so that it is ready to fill the airbag upon being dropped
  • Focusing on popping the canister prior to when it is necessary so that there is no delay related to the CO2 when the device is dropped

Challenges

• Safety
  • Premature detonation of our airbag system (Literally blowing your pants off)
  • Working with pressurized systems of CO2 which have the possibilities of exploding
• Cost
  • Airbags are expensive and typically designed to only be used once
  • CO2 canisters are going to be needed in large quantities for testing (this will inflate our actual cost)
• Power
  • We need to power both an Arduino as well as a 12V solenoid valve, this requires an external power supply which will be part of our device
• Size
  • Creating a device small enough to maintain the shape and convenience of your device without compromising safety or efficacy
  • Working with sizing and space constraints of our parts and fitting them together in the most efficient way possible
• Airbag
  • Building an airbag which will deploy in such a way as to maximize protection but still deploy in time with no snags.
  • Able to absorb a blunt force impact
  • Easily deflatable for reuse
• Arduino
  • Code which effectively filters information in order to accurate determine if it is falling

Costs

Hardware and Circuit

• Arduino Uno (Provided by TA)
• Arduino Accelerometer (GY-521) ~ Provided, link
• STP36NF06L Transistor ~ Provided, link with link to data sheet

Valve and Tubing

• Threaded 3/8" 24 threads / inch, 16g CO2 Cartridges ~ $47.95 for 50, link
• McMaster-Carr tube ~ $15.20, link
• CO2 (3/8") to Regulator (1/4") Converter (Lafed by our TA)
• Pressure Regulator (1/4") ~ $22.48, link
• Regulator(1/4") to Valve (1/4") Attachment ~ $2.39, link
• Electronic (1/4") Solenoid Valve ~ $12, link
• Valve (1/4") to Hose Attachment (1/4") ~ $3.12, link
• Pneumatic Tubing (1/4" ID) ~ $7.31, link

Airbag Material

• Tyvek Cloth ~ $7.35, link

Total Cost ~ $117.69

Estimated Unit Cost ~ $46.54

• Estimated Unit Cost is determined by scaling our cost based upon mass production. In several cases, we had to buy bulk amount of materials but ultimately only used a small percentage of it. The estimated unit cost accounts for these and would represent the cost to make multiple Gravicases.
  • Example: we spent $7.31 to get 10 feet of pneumatic tubing but ultimately used a little bit less than half of a foot of it. Therefore we would be able to build 19 more Gravicases without having to spend any additional money on pneumatic tubing.
  • This was the case for the Tyvek material (1/10), pneumatic tubing (1/20), CO2 canisters (most of their use was in testing causing a big spike in our total cost), and the McMaster-Carr tube (1/25).
    • Values are ratios of the amount used compared to the total

Gantt Chart