GraviCase Log

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Weekly Log for GraviCase Project

By Matt Rocco and Michael Morgan

Link to the GraviCase wiki Page: here.

Week 1 (September 1 - September 5):

"Decided" on project, started to gameplan objectives and obstacles of project, began to think of how to accomplish goals and design / build our project. Ironing out details on what skillsets we will have to pick up / refresh to accomplish our design. Created wiki and weekly log.

Week 2 (September 5 - September 12):

Due to concerns about both the feasibility and safety of our project, we have begun researching into some of the individual parts of our project. We want to make sure that we can come up with a cheap effective way to make and test our project. We see the airbag portion of our idea as the elephant in the room as far as cost is concerned. Additionally, we have begun research into a way to inflate our airbag safely and quickly enough to meet the safety and usefulness goals we have set for our project. While originally we were leaning towards a chemically inflated airbag, through consultation with out TA, we believe a compressed air inflation will be 1 safer, 2 cheaper, and 3 most realistic. We have begun looking into personal airbags which inflate from compressed air and starting to run some of the cost numbers as well as the ability for us to reverse engineer the deployment system for a smaller airbag. We need to begin designing our product, specific concerns we have are the powering mechanism, the airbag shape, the airbag inflating mechanism, preventing premature / unnecessary inflation of the airbag and also the speed at which we can fill the airbag (as it must be able to inflate in the time it takes for the phone to hit the ground. We have a few ideas related to this: we have a rudimentary idea of how we want the airbag shaped. However, more research and discussion is necessary for the powering and inflating parts of our project. I have an idea related to a CSE132 lab I did involving peak detection to count "steps" on the arduino platform, and we believe that this may be the most effective way for us to ensure it doesn't inflate prematurely.

Week 3 (September 12 - September 19):

We met with our TA, Andrew, on Tuesday and Professor Feher on Friday to discuss our project and we have moved towards the idea of our project being more of a prototype then a finished project. We also opened ourselves up to the idea of it being a case for any electronics which would help with our size constraints.

  • One issue we still have is with safety
    • Through our meetings we have discussed our accelerometer peak detection idea which we see as viable and if we transition to a non phone case this will allow us to not worry so much about everyday movement.
    • Additionally we have decided on compressed air as our main method of airbag filling, and while we were worried about our method of puncturing it, Andrew told us he believes there is a valve attachment for Arduino which we could use. We have begun researching this and currently it is our primary way of filling our airbag.
      • We believe compressed air will be much safer than the chemical explosion used to fill a car airbag, it also makes it easy to replace and test the airbag with refillable CO2 cartridges.
  • Our other main obstacle is cost which is primarily due to the airbag:
    • Andrew recommended trying to make our own, or at least experiment with makeshift materials so we could get an idea as to the shape and size of the airbag.
      • We were unable to get out this weekend to get testing materials, but we plan on doing so later this week. However, the main focus of our past week has been on improving the website and also working out the cost related issues of our project.
    • Professor Feher recommended finding someone with origami skills so that we could work on an efficiently folded and easily deployable airbag. He also agreeded with Andrews suggestion above and suggested that once we got the shape and size of our airbag down that we try to find people with structural engineering / material science backgrounds to help us find a workable and durable material.

Week 4 (September 19 - September 26):

We purchased some materials to test airbags (glue gun and trash bags) and intend to do some minor designing and testing work on the shape and packaging of our airbag with trash bags before working on finding a more suitable / long term material.

  • Michael Morgan has begun work on airbag design.

I (Matt Rocco) refreshed myself on Arduino today, discovering some Mac compatibility issues with the program. However, after taking an hour to resolve those issues, I wrote a rudimentary blink program just to confirm my understanding of the code. I have begun working on a program for our accelerometer which would send voltage to a port after sensing that it was being dropped (3 hours). Recap:

  • Wrote basic blink program
  • Began work on an accelerometer triggered.
    • We believe that we can power our valve by sending voltage (which we may have to step up / transform) through one of our ports so this is out intent with the accelerometer program.

MorganRocco4EVA (talk) 19:08, 24 September 2017 (CDT)

Week 5 (September 26 - October 3):

We started experimenting more quantitatively with our airbag design with a large focus on volume.

  • We have determined that an 8 oz. cartridge of CO2 is the most cost effective and also the best size.
    • We found that 1 gallon of air amounts to 7 grams of compressed CO2, so generally we know that 8 oz. of CO2 will give us a little more than a gallon of volume in our airbag.
      • In order to discover the approximate volume of our airbag, Michael Morgan filled it with water and then measured the amount of water we needed to fill it. We found this amount to be about 12 cups of water (3/4 of a gallon), however, in our final design we would like to have a larger airbag so we believe that the gallon of air that we will get from the 8g CO2 cartridge that we get will be perfect.

Matthew also continued work on the Arduino code: hooking up the accelerometer to the Arduino and beginning to figure out a method to make our case feel that it is dropping. Additionally, thanks to a suggestion from a fellow ESE 205 student during our presentation, we plan on incorporating "tumbling" into sensing if our device is dropping.

  • A falling phone is likely to "tumble" / flip around as it falls, we can sense this with a gyroscope (which we have on our accelerometer model: GY-521). If we incorporate this into our formula for falling, we believe it will lead to an overall safer and less likely to inflate at the wrong time airbag design.

MorganRocco4EVA (talk) 20:53, 1 October 2017 (CDT)

Week 6 (October 3 - October 10):

We ordered our parts for the mechanical side of the project:

  • A 12V DC solenoid valve
    • It is larger than we expected (no description of its size online) so it is a new found challenge, however, now we have some physical objects which we can start positioning to get an idea for the layout of our project's shape and design.
  • Pneumatic tubing
  • 16 oz. CO2 cartridges (8oz. are more expensive relatively so we intend to get 2 airbag "fills" per cartridge
    • We have ran into a cost related problem with CO2 cartridges as they are not as cheap as we recall seeing when we looked earlier.
  • Hose clamps and some valve attachments in order to connect the various parts

We have begun laying out the components, but we have also started designing the systems connection to the airbag. Due to getting the wrong sized valve attachment on the CO2 to solenoid valve end, we are currently only working on the valve through to the airbag side of the system so far. Later this week I intend on writing some quick code to ensure my understanding of the valve is correct and to see that it opens quickly enough. After that is successful, we will integrate that with our existing code and then begin integrating that into the system as a whole. Additionally, Michael has been focusing on refreshing himself with CAD and 3-D printing as we see ourselves transitioning towards that when we begin to tackle mounting the components of our system onto a case or other kind of harness. Continued work on Arduino code:

  • Needs to sense that it is dropping (z input from Accelerometer)
    • Setting a threshold amount for it falling so that it does not go off when unnecessary
  • Needs to be able to sense it is tumbling (gyroscope)
    • Setting a tumbling threshold for both values so that it does not blow up unnecessarily

Creating a rolling average of accelerometer and tumbling data so that the Arduino can decide if it being dropped

    • Deciding on size of buffer

MorganRocco4EVA (talk) 12:59, 9 October 2017 (CDT)

Week 7 (October 10 - October 20):

We have all of our parts, and have drawn up some preliminary designs for the layout of the case.
Early Design Concept 10.10.2017

  • We have some minor size issues related to our valves, but we plan to go and get adapters or print them ourselves.
  • At the suggestion of our TA, Andrew, we are looking into getting sealant to apply to our various connectors so that they will remain airtight
    • Depending on how permanent the sealing material is, we may only apply it to the static parts of our system (i.e. avoiding it on the CO2 screw in location because it needs to be swapped in and out as it runs out).

Michael is designing a 3D printed part which will screw into the CO2 side of our valve.

  • This component will have a sharp point facing the side where the CO2 cartridge is inserted.
    • The purpose of this piece is to puncture the CO2 cartridge so that it is ready to go once the solenoid valve switches open.

I am continuing work on the accelerometer code (5 hours)

  • I have been working on how to compactly wire the accelerometer to the Arduino so that the system is robust (as it is being dropped as well as attached to an exploding airbag) and also space efficient.

We have fallen behind a little on the airbag design, currently we need to focus on how to shape it so that it can protect the sides and front of the device.

  • The working idea we have right now is a sort of trough like design. However, we do not know how to build a deflated airbag which fills to this parameter.

Week 8 (October 20 - October 23):

Thanks to a suggestion from Andrew, in addition to creating our original idea on how to puncture the CO2 cartridge, we are also looking into hollowing out (drilling a hole through the middle of) a bolt which we would screw into the CO2 side of our valve that will function as an adapter between our valve and the CO2 cartridge. We are still working on ways to attach some kind of spike to this adapter so that the CO2 cartridge punctures when it is screwed into place.

  • At Andrew's suggestion we popped a CO2 cartridge into our airbag system so get an idea of if our earlier approximations were accurate.
  • We ran into a new obstacle, which is the CO2 cartridge getting fairly cold (frost build up on the cartridge) as it is dispensing air. However, we do not think that this will effect performance of our device, it will only make it a little cold to replace.
  • We also did a quick test of our DC solenoid valve, we ran DC current from a wall outlet into it to make sure that it opens and closes.
    • While you cannot really see it opening, the valve makes a distinct click when you plug run voltage across it
    • I did a quick test with water (as we do not yet have our CO2 linked up with our valve) and the water does not flow through the valve until voltage is run across it, as expected.

I am continuing work on our code (2 hours)

  • Currently we have our raw values from the accelerometer and gyroscope (we found code for this online, and I spent time making sure that I understand it)
    • My goal for the middle of the week is to process these raw values into ones that we can actually understand, and then use these to calculate whether or not our device is falling
      • Once this is done, we will draft up a circuit so that we can run the correct amount of voltage through in order to power the valve (which will likely need an external 12V power supply, as the Arduino can only output 5V)