Mechanical Engineering Report:

P13022 Internal Device

Author: Nicholas Dominesey

Date:___ _May 7th, 2013_

Materials

Original Specs:

  • Biocompatible.

Optional Methods for Achieving the Spec:

  • Titanium

Chosen Method:

  • Titanium
  • No attempt was made to use Titanium.

Executed Method:

  • Clear Plastic (non-Acryllic)
  • Successes:
  • Durable
  • Easy to Manufacture
  • Meets the needs of the current project
  • Failures:
  • Retains heat (poor conductivity)
  • Bulky
  • Action taken to resolve failures:
  • None taken

Testing:

  • Heat generation tests were performed to determine the temperature increase of the device under operating conditions.
  • A thermocouple/thermometer device was used to measure the temperature within the case, on the surface of the case and the ambient air temperature.

Conclusions about the design:

  • Given the time and financial situation, this solution was best.
  • Shortfalls:
  • Exceeds desired size.
  • Recommendations:
  • Order custom batteries that are smaller and offer a custom fit
  • Use a more conductive metal
  • Make the device into a smooth shape and remove edges (like an M&M)

Possible Next Steps:

  1. Plastic Prototype of M&M shaped case that is capable of holding the current circuitry, micro-controller and AA batteries.
  2. Prepare to shrink down the case when electronic upgrades allow for it.
  3. Experiment with Aluminum M&M shaped case through CNC machining.
  4. Use of a gasket to waterproof the design.

Design & Configuration of Parts within the Device

Original Specs:

  • N/A

Optional Methods for Achieving the Spec:

  • Minimize size of case as much as the electronic equipment will allow.

Chosen Method:

  • Size the case based on the length and width of the circuit board and height of the electrical components.
  • Successes:
  • The height of the case was suitable for the electronic equipment and worked well when the AA battery system failed allowing us to implant the original, larger batteries.
  • Failures:
  • Adding a quarter inch of clearance for the circuit board ended up not being enough to account for the pin connectors and wires.
  • Action Taken:
  • New side walls were cut so that they would fit outside of all the existing pieces. We were able to save 4/6 sides by doing this allow this was not an ideal design for the box.

Testing:

  • No tests were performed to evaluate the design, strength or waterproofing of the internal device case.

Conclusions about the design:

  • For our purposes, the design worked well for us. Although it is not implantable, it does feature several advantages.
  • The clear sides allowed for us to foresee any issues with smoke that may have occurred.
  • The board over battery/micro-controller configuration was chosen because it seemed like the most compact solution at the time.
  • Shortfalls:
  • [List of problems encountered with the chosen solution.]
  • Not knowing the exact size of the board until there were only a few weeks left before the end of the project really set back the time allotted to build the case.
  • Miscommunication and lack of exact detailed plans between the EEs and MEs may have added to the failure of adequate size for the case.
  • The case is quite thick.
  • Recommendations:
  • As mentioned before, an M&M shaped box would be more ergonomic.
  • Reduce size of internal circuitry
  • Finding a way to fit small batteries in between the electronics and moving the electronics around in order to account for this could save some room.
  • Using the programming board to configure a chip to be used on the circuit board would have saved a lot of room when compared to the micro-controller that was used.
  • Reducing the size of the relay would allow for decreased packaging size as well.
  • Allow plenty of time to construct a prototype case and final case.
  • Strong communication between the EEs and MEs will determine the success of the subsystem.

Possible Next Steps:

  1. Reduce size of internal components.
  2. Work with EEs to manipulate electronics and battery configurations to your advantage.
  3. Create a scaled mock-up of the circuit board, batteries, case and all other components using either CAD modeling and/or plastic prototyping (which would be better in the end than just a CAD model).
  4. Move towards a final case design from the lessons learned in prototyping.

Interfacing with P13021

Original Specs:

  • N/A

Optional Methods for Achieving the Spec:

  • Create duplicate case for P13021’s use.
  • Remove and replace our outgoing cable with the other team’s wires/cable and screw directly into pin connectors on the board.
  • Add a port into the case and allow for P13021 to tap in at will.

Chosen Method:

  • Add a port into the case and allow for P13021 to tap in at will.
  • Successes:
  • Successful integration of a sturdy port into the cover of the case.
  • Allows for instantaneous connection/disconnection with team P13021’s device.
  • Allows for an external power supply to charge the batteries using the battery charging adapter.
  • It made use of the ports we initially planned to use for the breakaway port and reduced the amount of wasted parts in the project.
  • Failures:
  • Could be more discrete and flush with the side of the case.
  • Could have a cap to put over the port when not in use.
  • Action taken to resolve failures:
  • N/A

Testing:

  • No official testing has taken place regarding the interfacing port.
  • However, the port has been pulled and pushed on several times and remained firmly glued into place.
  • The port has been used and proved that it is capable of charging the batteries.

Conclusions about the design:

  • The design was a great use of existing materials that otherwise would have gone to waste. The port itself may be a little overkill but it certainly worked out to our advantage since we were limited on time and budget.
  • Shortfalls:
  • Limited testing has been conducted to prove successful interfacing with P13021.
  • Recommendations:
  • In future designs, perhaps a cheaper solution is available.
  • Consider using common plugs/ports such as USB.
  • The use of epoxy or a strong bonding material to secure the port.
  • Press-fit.
  • Welding.
  • If possible, make the port for the outgoing breakaway cable and the interfacing cable one and the same.

Possible Next Steps:

  1. The next steps for the interfacing port are dependent on the design of the entire case including material and design.