Design Project



Homework 4: Packaging Specifications and Design

Team Code Name: RoboSiM Group No. 11

Team Member Completing This Homework: Miles Whittaker

E-mail Address of Team Member: mjwhitta@purdue.edu

Evaluation:

|SCORE |DESCRIPTION |

|10 |Excellent – among the best papers submitted for this assignment. Very few corrections needed for version submitted in Final |

| |Report. |

|9 |Very good – all requirements aptly met. Minor additions/corrections needed for version submitted in Final Report. |

|8 |Good – all requirements considered and addressed. Several noteworthy additions/corrections needed for version submitted in |

| |Final Report. |

|7 |Average – all requirements basically met, but some revisions in content should be made for the version submitted in the |

| |Final Report. |

|6 |Marginal – all requirements met at a nominal level. Significant revisions in content should be made for the version |

| |submitted in the Final Report. |

|* |Below the passing threshold – major revisions required to meet report requirements at a nominal level. Revise and resubmit.|

* Resubmissions are due within one week of the date of return, and will be awarded a score of “6” provided all report requirements have been met at a nominal level.

Comments:

Introduction

RoboSiM is intended to be a small and stealthy surveillance platform. For this reason, it is important for all the components to fit neatly into a compact package that makes very little noise. The project cannot be too small, or it may not be able to handle terrain that gets too rugged. Also, the project cannot be too big, or it would be easily noticeable, inhibiting its ability to be stealthy. To keep our design as inaudible as possible, we may insulate the final prototype with sound dampening material.

Commercial Product Packaging

We have identified two products that are similar to ours. The first is the SRV-1 Blackfin Mobile Surveillance Robot [1], and the second is the WowWee Rovio Mobile Webcam [2]. The Blackfin is closest to the design that we would like to achieve, but both of these products are used for capturing video footage so we will need to adapt our product to be able to record audio in lieu of video capture.

Product #1

[pic]

The SRV-1 Blackfin Mobile Surveillance Robot is an R/C toy that allows the user to explore the terrain of a home or office. One really nice aspect of its design is that the entire package fits in your palm. Instead of the typical 4-wheel R/C car, the Blackfin uses tank-like treads to navigate the desired location. The Blackfin is Java-based and can interface with a PC using Wi-Fi. This connectivity allows the robot to be remotely controlled using a web server.

Among the design's positive features are its tank treads. They allow the robot to navigate rugged environments with very little resistance. Additionally, the palm-sized packaging improves its stealth characteristics.

The Blackfin’s electronics are not enclosed, meaning that any noise created is not dampened, rendering stealth much more difficult. While this may not be a problem for something as small as the Blackfin, our RoboSiM will be larger and will have motors that may create a substantial amount of noise. RoboSiM will emulate the Blackfin's tank treads and compactness, but we will differ from it because we will need to record audio as opposed to video.

Product #2

[pic]

The WowWee Rovio Mobile Webcam is a robotic sentry that can be programmed to follow up to 10 paths in an indoor environment. Any device capable of browsing the internet is capable of controlling the Rovio and monitoring its progress along the programmed paths. We have considered creating a 3-wheeled package to save power and create a quieter product, but in the end we decided that tank-like treads would be better suited for rugged terrain (which is the intended application).

While having a microphone raise up once our project has reached its location would protect the microphone from any unwanted damage during transit, it would also introduce unneeded mechanical complexity. Though our final project may be close to the size of the Rovio we would like to aim for something smaller. Also, using three wheels in the same manner as the sentry would be complicated due to the embedded wheels that allow for perpendicular motion with respect to the wheel. In the end, our project may resemble the Rovio's size and will be enclosed to protect the components from the environment. However, it will differ in almost every other way.

Project Packaging Specifications

We intend to start with the RP5 Tracked Chassis manufactured by Pololu [3]. From there we will build upwards, mimicking the SRV-1 Blackfin Mobile Surveillance Robot. The final product is intended to be as compact as possible to minimize visibility. The included motors may need replaced to save power consumption and to decrease audible noise generation. In addition, we will add an omni-directional microphone [5] to the front, along with three ultrasonic sensors [4] (one to the left, one to the right, and one to the front of the chassis). We considered using Velcro to attach the sensors and microphone in case they later needed replaced, but there may be issues with static electricity associated with that approach. For now we are exploring the possibility of expansion platforms (manufactured by Pololu) that the RP5 supports. The expansion platforms will be useful since it may be impractical to fit everything on a single layer while providing mechanical protection to the PCB. A concept CAD drawing is attached to this document. We estimate our final product will weigh about 1 lb.

PCB Footprint Layout

The major PCB-mounted components of this design and their packaging are summarized in the following table:

|Device |Standard Package |Length (mm) |Width (mm) |Height (mm) |

|PIC24HJ128 |64-pin TQFP |10 |10 |1 |

|VS1053B |48-pin LQFP |7 |7 |1.4 |

|MMC Bay |N/A |27.5 |29.1 |2.2 |

|3.3V Regulator |4-pin HSOP |10.67 |14.73 |10 |

|7.2V Regulator |4-pin HSOP |3.1 |3.1 |10 |

|12-pin Header |Breakaway Header |10 |2 |4 |

|4-pin Header |Breakaway Header |6 |2 |4 |

|H-Bridge |20-pin HSOP |16 |14.45 |3.4 |

For both the microcontroller and the audio codec chip, we have selected small surface-mount packages (TQFP and LQFP) because the through-hole variants are excessively large due to the pin count. These will be a technical challenge to manually solder, which is why we are planning to install sockets on the PCB instead of mounting the chips directly to the board.

The packaging choices were less flexible for the regulators and H-bridge chips, as the chips we have selected are offered in 4-pin HSOP only. Conveniently, these packages are surface-mount ready and relatively compact.

The size of our PCB will be smaller than the internal area of the RP-5 chassis, so we can choose an arbitrarily large (or small) board as long as the components fit. Because we will have both high-power (voltage regulators and motor controller) and low-power (microcontroller, encoder) components on the board, it is desired to separate each type. As can be seen on the preliminary PCB layout (Appendix C), the rear half of the board will contain the high-power components and the front half of the board will contain the low-power components.

We are considering installing expansion boards in the robot’s bay that will allow us to build the robot vertically. The top-most expansion will be the base upon which the sensors and LCD will be mounted; this allows us to conserve PCB space by interfacing via headers (rather than mounting the devices directly on the PCB. We estimate that a 4in x 4in board will be sufficiently large to contain all of the components and provide the necessary separation. This size board will also allow us to place the PCB inside the bay of the rover, protecting it from the elements.

Summary

To meet the design objectives it is important for all the components to fit nicely in a compact package that makes very little noise. To achieve this, we are going to emulate the shape of the Blackfin and enclose it like the Rovio. The robot's dimensions will be 7” x 5.5” x 4.5” (with room for vertical expansion) and weigh about 1 lb. The construction of the robot will be modular and maintainable. The PCB will be arranged in a manner that separates low- and high-power devices (to minimize interference); we chose a board size of 4” x 4.5”. All external sensors will be connected to the main board via headers to facilitate easy modifications in placement and to distance the PCB and microcontroller from potentially harsh environments.

List of References

"ThinkGeek :: SRV-1 Blackfin Mobile Surveillance Robot." ThinkGeek :: Stuff for Smart Masses. Web. 09 Feb. 2010. .

"WowWee Rovio Mobile Webcam - RobotShop." RobotShop - Personal and Professional Robots, Robot Parts, Robot Kits, Robot Repair. Web. 09 Feb. 2010. .

“DFRobot Mobile Tank Base - RobotShop." RobotShop - Personal and Professional Robots, Robot Parts, Robot Kits, Robot Repair. Web. 11 Feb. 2010. .

"SparkFun Electronics - Ultrasonic Range Finder - Maxbotix LV-EZ0." SparkFun Electronics - News. Web. 09 Feb. 2010. .

"668-1155-ND (Manufacturer - POM-2735P-R)." Digi-Key. Web. 11 Feb. 2010.

"PIC24HJ128GP306-I/PT-ND (Manufacturer - PIC24HJ128GP306-I/PT)." Digi-Key. Web. 11 Feb. 2010. .

"SparkFun Electronics - Basic 16x2 Character LCD - White on Black 3.3V." SparkFun Electronics - News. Web. 11 Feb. 2010. .

"BATT PACK 7.2V AA BUTTON NIMH - HR-3U-2500L2X3." DigiKey Corp. | Electronic Components Distributor | Greece Home Page. Web. 11 Feb. 2010. .

"SparkFun Electronics - Compass Module - HMC6352." SparkFun Electronics - News. Web. 11 Feb. 2010. .

"SparkFun Electronics - SD/MMC Socket for Secure Digital Disk or Multi Media Cards." SparkFun Electronics - News. Web. 11 Feb. 2010. .

"SparkFun Electronics - Venus GPS Logger with SMA Connector." SparkFun Electronics - News. Web. 11 Feb. 2010. .

"SparkFun Electronics - Antenna GPS 3V Magnetic Mount SMA." SparkFun Electronics - News. Web. 11 Feb. 2010. .

"PG164120-ND (Manufacturer - PG164120)." Digi-Key. Web. 11 Feb. 2010. .

Appendix A: Project Packaging Illustrations

[pic]

Appendix B: Project Packaging Specifications

|Vendor |Manufacturer |Part No. |Description |Weight |Tooling |Unit |

| | | | |(g) |Requirements |Cost |

|Digi-Key |Micorchip |PIC24HJ128GP306 |16-bit microcontroller |0.43 |In-circuit |$6.66 |

| | | | | |programmer | |

|Sparkfun |Maxbotix |LV-EZ0 |Ultrasonic Range Finder |4.3 |none |$27.95 |

|Sparkfun |Sitronix |ADM1602K |16x2 Character LCD |10 |none |$14.95 |

|Digi-Key |FDK America Inc. |HR-3U-2500L2X3 |7.2V 2300mA Battery Pack |100 |none |$33.46 |

|Sparkfun |Honeywell |HMC6352 |Digital Compass |0.14 |none |$34.95 |

|Sparkfun |4UCON Techonology |PP-14446 |SD card socket |0.1 |none |$3.95 |

|Digi-Key |PUI Audio |POM-2735P-R |Omni-directional Microphone |0.15 |none |$2.94 |

|Sparkfun |Sparkfun |GPS-09171 |GPS Logger with SMA Connector|5 |none |$59.95 |

|Sparkfun |Onshine |ANT-555 |Antenna GPS 3V Magnetic Mount|80 |none |$12.95 |

| | | |SMA | | | |

|RobotShop |- |RP 5 |Tracked Chassis |150 |none |$35.00 |

|- |- |- |Motor |N/A |none |$15.00 |

|- |- |- |Supporting Hardware (Wiring, |40 |none |$25.00 |

| | | |Passives) | | | |

|Digi-Key |Microchip |- |Programmer / Debugger |N/A |none |$34.99 |

| | | |Total Weight (lbs) |0.88 | | |

Appendix C: PCB Footprint Layout

[pic]

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