P18311: Sensory Exploration Development Platform
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

During this phase of the project, the team worked together to put together a preliminary detailed design based on the system level design phase of the project. The preliminary detailed design consisted of identifying the necessary hardware necessary for the both the Band Toy and MoonPad projects. The overall goal of this is to create a bill of materials for the final project.

Band Toy GPIO

Band Toy GPIO

Band Toy GPIO

MoonPad Inputs

The following sections explains the hardware selection process for the inputs of the MoonPad.

Pressure Sensor

A pressure sensor surface was required of the MoonPad to detect that the pad has been stepped on. Previous versions of the MoonPad used small FSR’s (Force-Sensing Resistors), which were 13mm diameter (circle) sensors that would only detect pressure if specific points on the moonpad were stepped on. To read a wider range of pressures, allowing more forgiveness to where the user steps, a larger FSR was selected providing an active area of 38mm x 38mm square surface with an operating force of from 0.04 lbs to 4.5 lbs. The total dimensions including the leads is 43.7 x 83.8 x 0.46 mm.

SD Card Slot

A Hirose Electric Co. LTD microSD card connector with hinge-manual insertion and ejection of the SD card. This surface mounting component will hold the SD card and has latching capabilities to secure the SD card. The dimensions for the microSD card connector is 13.8 x 14.1 x 1.83 mm.

Charging Port and Circuit

An Amphenol FCI micro USB 2.0 connector was chosen for charging capabilities and being able to download data to the programmable Xbee chip or the processor. The charging circuit is a Texas Instruments component which is 4.0 x 4.0 x 0.9 mm. The charging circuit can operate at a maximum of 1.1A input for recharging the AAA batteries.

MoonPad Outputs

The following sections explains the hardware selection process for the outputs of the MoonPad.

Speaker

Buzzer

A Piezoelectric buzzer was selected to for high performance and extremely low power consumption. The selected component operates at a frequency sound pressure of 4kHz and functions at 3V. The dimensions for this buzzer are 12.2 x 19.0 mm long including the terminal leads.

LEDs

Red, green, and blue LEDs were chosen to encompass three different output options. Wurth Electronics Inc. diffused LEDs were selected that produce a typical 140mcd for luminous intensity. The dimensions for all of these LEDs are 8.95mm tall including the leads, and 5mm in diameter.

Battery

The battery that was selected for this project focused on voltage, duration, size, chemistry, and being rechargeable. The batteries that were selected are TrustFire 10440 AAA batteries. These are Lithium rechargeable, 3.7V, 600mAh batteries sold via Amazon. Voltage will be stepped down to the operating voltages for the subsequent components in the configuration.

Battery Holder

A two cell battery holder was chosen in order to fully contain enough battery length to last for 6-8 hours of run time. A Keystone Electronics battery holder was chosen that includes a holder, cover, and red and black 26 AWG leads. This will provide roughly 7.4V for the entire configuration that will be lowered to the operating voltages for the components. The dimensions for the battery holder is 62.99 x 26.01 x 16.00 mm.

Processor

The microcontroller/processor for this project should be able to decode MP3 or WMA formats as well as still provide enough power and memory to operate it’s outputs. The Microchip 32-bit PIC43 MCU family supports music applications and is based on the a MIPS core. The PIC43MX795F512 MCU with 512 Kbytes of flash and 128 Kbytes of SRAM is used. The PIC32 supports the open source Helix MP3 Decoder Library by Microchip. The 32-bit microcontroller has low-power management modes (sleep and idle), integrated power-on reset and brown-out reset. The supply voltage, Vdd, for the processor is 2.3 - 3.6V. Package is 64 -TQFP (64 pins), where up to 51 are I/O pins. The contact/lead pitch is 0.50 and the dimensions for the MCU is 10 x 10 x 1 mm.

Xbee Chip

Two separate Xbee chips were selected for this project from Digi International. The first of which is a programmable Xbee chip that will communicate using the Zigbee protocol. This chip has 15 I/O pins, 32 kB of Flash and 2kB of RAM. The second chip selected was a non-programmable Xbee chip that will use the processor and the Zigbee protocol for the communication. Both chips have dimensions of 24.38 x 32.94 mm and utilize SPI or UART interfaces.

Bill of Material (BOM)

Band Toy

Band Toy Bill of Materials

Band Toy Bill of Materials

MoonPad

MoonPad Bill of Materials 1

MoonPad Bill of Materials 1

MoonPad Bill of Materials 2

MoonPad Bill of Materials 2

Preliminary Schematics

Band Toy

Band Toy Preliminary Schematic

Band Toy Preliminary Schematic

MoonPad

MoonPad Preliminary Schematic

MoonPad Preliminary Schematic

Test Plans

Having all of the parts arrive by the end of the semester will allow for the preliminary testing to occur. Small programs in software will be created to test hardware components and verify functionality. This will provide ease of use and understanding of the hardware before it comes time to build the entire configuration.

Plans for next phase

The goals for the next phase are to have a detailed Printed Circuit Board (PCB) layout with components layed out. This will include orientation, placement, and organization of the hardware used on both Band Toy and MoonPad projects. AutoDesk’s Eagle software will be utilized for the creation and design of the PCB layout. Furthermore, all of the components and hardware should be ordered by the end of next phase.

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