Veyebrations Provides vision aid to the visually impaired

Dylan Ayrey, Raymond Dodge, Joshua Pueschel Friday, May 15, 2015

Veyebrations 1

Table of Contents

Overview………………..…………………………………………………………….2 Need statement………….………………………………………………………2 Objective statement……………………………………………………….…….2 Description…………………………………………………………….…………2 Marketing diagram…………………………………………….………………...3

Requirements……………………………………………….………………………..4 Customer needs specifications………………….……………………………..4 Engineering specifications………………….…………………………………..4

Concept Selection…………………………..………………………………………..5 Market alternatives……….……………………………………………………...5

Design…………………….…………………………………………………………..6 Level 0………….………………………………………………………………...7 Level 1…….……………………………………………………………………...8 Types of proximity sensors:.......………………………………………………8 Radio Frequency module………………………………………………….….12 User interface:………………………………………………………….……...13 Kill Switch:………………………………………………………….…………..13 Background…………………………………………………….………………13 Multidisciplinary aspects………………………………….………………......14 Engineering standards………………………………...……………………...14 Outside Contributors………………………………...………………………..14

Constraints and Considerations……………………………………..…………..14 Cost estimates……………………………………………………….….………...16 Testing strategy…………………………………………………….……………..17 Risks…………………………………………………………….….………………20

PCB risks…………………………………………………….………………..20 Enclosure risks……………………………………………….……………….20 Coordination­related risks……………………………………………………21

Milestone chart…………………………………………………………………….22

Veyebrations 2

Overview

Need statement There are currently 6,670,300 visually disabled people living in the US and less than 3% of those people have seeing eye dogs. Dogs are also limited in what they can tell users and training a seeing eye dog can cost $42,000 or more. Existing vibration technology for the visually impaired has a limited range restricting a user to objects touching the ground. They can usually only sense up to 15 feet and can cost as much as $1000. There needs to be a cost effective alternative for the visually impaired.

Objective statement The objective of this project is to design and prototype a device that will make visually impaired people able to sense their environment better by using proximity sensors to alert the user with varying degrees of vibration. The device should have an option to be turned off. The modular design will allow users to rotate the device in a 3­dimensional space and sense all around them. The device should fit in a user’s hand and be comfortable. The device should not interfere with other nearby devices and should be compatible with multiple devices if a user wants to use more than one.

Description This system aids visually impaired people to navigate rooms and hallways. It uses a microcontroller and a proximity sensor to control a vibrating motor. The strength of the vibration is exponentially proportional to the distance the proximity sensor detects. The output from the microcontroller is amplified and fed into the vibrating motor. A temperature sensor is a part of the system to increase accuracy. The device has a number of enclosure options which should roughly fit in the palm of a user’s hand.

High level diagram

Veyebrations 3

Marketing diagram

Veyebrations 4

Requirements

Customer needs specifications I. System should be affordable II. System should have real­time feedback III. System should be easy to use IV. System should function in a room or hallway V. System should be able to function for at least an hour VI. System should work in harsh weather VII. System should be comfortable VIII. System should be durable IX. System should be able to be turned on and off

Engineering specifications Engineering Requirements Analysis Customer need

mapping

1 The manufactured cost should not exceed $100

The system should consider the cost of each component when making selections. For example Lidar is far more expensive than Ultrasonic. Cost should be of high importance when making these choices. PCB designs should be minimized to reduce cost. Open source PCB components should be analyzed and modified to remove unused aspects of existing designs.

I

2 The system should have no more than 200ms latency

From when the sensor probes the environment, to when the motor begins to vibrate the appropriate level latency should be 200ms. This is because that is what humans perceive to be instantaneous.

II

3 The system shall have no more than three buttons or switches for user input

There should not be lots of buttons and settings; it should be very simple and ready to go. It should not need calibration or have any setbacks to stop it from functioning immediately after turning the device on.

III

4 The system shall measure distances within a tolerance of 1 inch at a range from 1 to 10 feet

When choosing the sensor, the range should be taken into account. It should be able to function in a room 10x10x10 feet.

IV

Veyebrations 5

5 The system shall provide feedback following a 1/distance curve. The maximum displacement with no feedback will be 2 feet.

The system needs to provide more feedback when closer to an object and less feedback when far away. The rate that this feedback increases should follow a 1/distance curve.

IV

6 The system’s battery life should last for 1 hour without recharge or replacement

The system needs to accommodate a battery that can last a reasonable range of time without recharge or replacement

V

7 The system shall measure distances specified in Engineering Specification #4 from ­20 °C to 50 °C

The speed of sound changes speed with changes in temperature. In order to minimize the error of the calculations within the microcontroller, a temperature sensor will be used.

VI

8 The system shall measure distances specified in Engineering Specification #4 from 0% humidity to 100% humidity.

The speed of sound changes speed with changes in temperature. In order to minimize the error of the calculations within the microcontroller, a temperature sensor will be used.

VI

9 The system should not exceed 2 in x 3 in x 1 in

The system will be an unobtrusive object that can be placed on an article of clothing. In order to be unobtrusive, the container for the system will need to have dimensional constraints.

VII

10 The system should function after a drop of 2 meters

The system needs to be able to withstand impact on the container and continue to work. This is important in the case of the container hitting an obstacle (E.g: Person puts their hand on the wall)

VIII

11 The system should have a kill switch to shut off all the motors

There are scenarios where a person will want to shut off all the motors on the device ( E.g If wants to sit down). In order to enable this, a button should be created that will signal all the motors to shut off.

IX

Concept Selection Several market alternatives were looked at when considering this design. Most importantly was the idea of what a blind person’s day to day life consists of was kept in mind. A product that can facilitate a blind person’s needs in a max range of conditions while still remaining

Veyebrations 6

non­precarious and affordable would be the ideal market solution. While no product managed to satisfy those conditions, several came close.

Market alternatives Dogs­ Dogs are used to help blind people get around. They cost $42,000 to train and require large upkeep costs. As a result of how expensive they are, less than 3% of blind people are able to own seeing eye dogs

Ultracane­ The ultracane is a large costly alternative or complement to a seeing eye dog. It costs around $1000 and is waved about on the ground. If an obstacle appears in front of the user the cane will vibrate to let the user know

Ray Electronic Mobility Aid for the Blind­ The Ray Electronic Mobility Aid for the Blind is a slightly cheaper alternative to the ultracane which costs $299.95. This device can detect objects 9.35 feet away and announce them to the user via an audible or vibrating signal 1

Normal Cane­ Normal canes can only tell a user if there is an object in direct contact with the cane. They cost around $10 and are limited to use on the ground.

Range Cost Comfortability Usability

Dogs 2640 feet $42,000+ 10/10 7/10

Ultracane 13 feet $1,000 8/10 5/10

Ray Electronic Mobility Aid for the Blind

9.35 feet $299.95 8/10 6/10

Normal Cane 3 feet $12 8/10 4/10

Dogs are expensive to train and upkeep. They are the primary motivation for looking for alternatives. The ultracane is a modification to a normal cane, and is therefore constrained to a cane form factor. The range is limited and the cost is unnecessarily high. Usability is limited to objects on the ground, and the cane can not be used in small spaces. The Ray Electronic Mobility Aid for the Blind is a near solution to what what is discussed in this proposal, however it is larger than our target design, the cost is higher, and the range is shorter.

This proposal takes the best properties from each of the market alternatives and makes a small low cost alternative. The Ray Electronic Mobility Aid for the Blind is extremely close to our design and form factor, however our design is going to be less expensive, smaller, and have a longer range.

1 “Ray Electronic Mobility Aid for the Blind”. Retrieved 2015­04­28. http://www.maxiaids.com/products/8274/Ray­Electronic­Mobility­Aid­for­the­Blind.html

Veyebrations 7

Design The level 0 design is the to

p­most level. This level is an overview of what a user experiences of our system. The user will need to supply power in the form of a micro usb cable. The userhas access to a power switch. The temperature sensor, the distance sensor input is not directly user supplied, but is determined by the user pointing the device at different objects. The user has physical feedback in the form of vibrations from the system.

Level 0

Veyebrations 8

System

Inputs Distance Measurement Temperature Power Power Switch Chirp [40 kHz audio]

Outputs Vibration Chirp [40 kHz audio]

Purpose The system takes input from the outside word and puts out feedback alerting the user their approximate proximity from objects.

The level 1 design shows the components that make the system and how they interact. There will be a PCB board which will have a temperature sensor, a radio transceiver, a microcontroller, and a power amplifier. Outside of the PCB board but still contained within the enclosure will be the distance sensor, a motor, and the power supply in the form of a battery which is supplied by the user. The microcontroller will be acting as the heart of the entire system. The microcontroller will be communicating with all of the sensors as well as supplying the motor with a signal to control its rate of vibration.

Level 1

Types of proximity sensors:

Ultrasonic Infrared LIDAR

Range 50 10­20m 40 5­10m 30 131m 50

Cost 50 $5 2 50 $10 45 $90 30

Score 100 90 75 80

Choice: The design choice is ultrasonic with the possibility of LIDAR as future planned obsolescence. Ultrasonic is a cost effective solution that will work reasonably well indoors. Infrared is a more expensive while is less accurate than the ultrasonic alternative. LIDAR is the most expensive but accurate enough to use in a variety of outdoor settings. This design will not make it into our first product release but there is the possibility of future iterations of the device containing LIDAR units.

2 The ultrasonic sensor costs $4, but using an Ultrasonic will also require a temperature sensor

Veyebrations 9

Distance Sensor (HC­SR04)

Inputs Distance Measurement [0 m, 5 m] Trigger [Digital Pulse] Power [5V] Chirp [40 kHz audio]

Outputs Chirp [40 kHz audio] ECHO [Digital Pulse] (Time that ECHO = HI is time between Chirp sent and received)

Purpose Perform Echolocation. Convert time for echolocation into electrical signal.

Model

The distance sensor is constantly sending out echos when in operation to determine distance to objects that it is being pointed at. The microcontroller is controlling the vibrating motor based mainly on the values read from this sensor.

Veyebrations 10

Temperature Sensor (MF52­103)

Inputs Temperature Power

Outputs Voltage

Purpose Convert ambient temperature into something the microcontroller can use. Specifically voltage because the microcontroller has an ATD.

The reason for measuring this is that the speed of sound varies significantly with temperature, and this measurement can be used to correct for this variable.

Model

The temperature sensor reads through an ADC input contained on the atmega328 microcontroller. This value is then be used to adjust for the speed of sound in order to measure a more exact distance measurement from the ultrasonic distance sensor.

Veyebrations 11

Motor

Inputs Signal [Pulse Width Modulation]

Outputs Vibration

Purpose Provide tactile feedback to a user

The motor receives a signal from the microcontroller on the PCB board. A power amplifier is used so that the signal sent from the microcontroller will be strong enough to actually drive the motor.

Microcontroller Program

Inputs Bit data (From Radio) Voltage (From Temp)

Outputs Signal [Pulse Width Modulation] (To Motor)

Purpose Intrasystem coordination

Technology The arduino framework will be used to program the ATMEGA328 microcontroller. This framework uses a language that is a subset of C.

The microcontroller program takes readings from all of the sensors. Once those readings have been taken, it converts all of those inputs into a vibration rate. The program then sets the motor to vibrate at a specific rate. Below is a subsystem that was depreciated from the final design. When tested, interference did not present itself as an issue, so to reduce cost and improve form factor, the radio controller was removed.

Radio Communicator

Inputs Radio Signals Data

Outputs Radio Signals Data

Purpose Intersystem coordination

Veyebrations 12

It is intended that multiple systems will be used in close proximity of each other, and without some form of coordination between them, it is very likely that they will interfere with each other.

Technology This radio unit uses a 2.4 Ghz band and a proprietary communication protocol to push packets to one another.

Radio Frequency module

Radio by purchasing spectrum

Bluetooth Wi­Fi

General (nRF24L01)

Integrated (nRF8001)

General Integrated

Cost .15 ­ ­ ­ ­ ­ ­ ­ ­ ­

Reliability .25 + + + + + + + +

Cooperation .25 + + + + + + + + +

Ease of Use .20 ­ ­ ­ ­ ­ ­

Power .15 ? 3 ­ ­

Security .05 ­ ­ ­ ­ + +

­0.70 0.60 0.65 0.35 0.40

An expensive option is licensing a range of radio frequency spectrum and exclusively broadcasting on that spectrum. This would ensure that the system will not interfere with other types of systems and that other types of systems will not interfere with this. However, this alone will not cause the system to not interfere with other instances of itself. In addition, licensing radio frequency spectrum appears to be expensive and requires dealing with each government that the product will interact with.

Another way is to implement communications using a wireless networking standard. Using one of these would require a transceiver for the specific frequency the standard uses, but the fact that these are public standard makes finding compatible chips more likely. This also intrinsically means the systems will not talk over each other. Bluetooth is one such networking standard, which communicates over 2.4 GHz.

There are several modules that can communicate on the bandwidth required for Bluetooth. One is "nRF24L01+". One of the other options is "nRF8001"; this is a transmitter that contains the

3 Average Current Consumption is 13.5 µA, accoring to http://www.nordicsemi.com/eng/Products/Bluetooth­R­low­energy/nRF8001

Veyebrations 13

entire Bluetooth stack, whereas the nRF24L01 uses a proprietary communication protocol. This means that the microcontroller would not contain code controlling communication protocol.

The range of the protocol is less irrelevant as the sonar device will be the limiting factor. Bluetooth can have an extremely short range in low power operation, so this might become important to consider.

Enclosure

Inputs None

Outputs None

Purpose Act as a container to protect/hold the PCB board, motor, and sensors.

Technology This unit will be 3d printed

User interface: The user will primarily be controlling the device through the kill switch. The device has an on state and an on/off switch the user will use to turn the device on or off. The user is able to point the device at various objects and right away they begin to get vibration feedback. When they are done using the device they can turn it off with the same switch.

Kill Switch: When designing a kill switch two options were considered; they are listed below

Wired Kill Switch: This option wires each device together in order to create a switch that will turn off all the motors. Cost is cheap, power consumption is low, and there are no interference implications.

RF Kill Switch: This option involves a button contained on each unit that will notify all connected units to turn off all motors. The cost is more so than a wired solution, power consumption is low relative to other components, and comfortability is increased. Engineering overhead is also a large consideration for this option. Making this function correctly and securely will increase engineering hours and possibly exceed the limitations of the microcontroller.

Choice: We chose the wired design due to the fact the RF module was depreciated from the design.

Veyebrations 14

Multidisciplinary aspects Computer Engineering courses were helpful in the following aspects:

Work with a microcontroller ­ atmega328 PCB layout

Computer Science and Software Engineering courses were helpful in the following aspects: Version control Programming

Electrical Engineering courses were helpful in the following aspects: Circuit design

Engineering standards Using arduino standard libraries Eagle design files CAD design files

Outside Contributors None

Constraints and Considerations Extensibility: The units are open sourced with a GPLv2 license to allow other people to hack on them. They take into consideration the possibility of upgrading the sensor. All the PCB designs created by us are open hardware as well. Manufacturability: The units have PCB designs that try to leverage surface mount components as much as possible to reduce manual soldering time. Form Fitting enclosures will be examined to take into account aesthetics on the final deliverable. Reliability: The devices are accurate within normal temperature and weather conditions on planet earth. The devices is able to function inside a normal size room or hallway and withstands the wear and tear of everyday use up to and including being dropped. The device has have a kill switch that will immediately turn off all of the motors contained on one’s person. Economic Context: The device costs lower than competitors while offering similar functionality. Production of the device will be fast and easy. Environmental Context: The open source design will hopefully allow for a global adaptation that will let impoverished nations utilize this cost effective alternative to dogs. Ethical context: These devices are aimed to help both the visually impaired and anyone who needs a device to “feel” distances based on vibrations. These devices are considered to be highly ethical and globally in demand. Health and Safety issues: These devices must be accurate enough to make the wearer comfortable with using them as a means to navigate a room. A false reading could lead to the user colliding with objects

Veyebrations 15

Intellectual Property: The source code will be held under the GPLv2 license. This means that anyone who gains a copy of this software will have no restrictions to fully modify the software for personal use. The software will contain a copyright notice and a permission notice which will fully describe the GPLv2 license. Political Issues: The device will have to pass FCC compliance. Sustainability: The device may not be as easily manufactured if one of the parts becomes outdated or no longer manufactured. One of the main motivations of open sourcing the design is giving others the ability to switch these parts out in the future.

Veyebrations 16

Cost estimates Type Part # Our cost ($) Cost ($) Our Shipping

Time Estimate

Temperature sensor

MF52­103

2.00 0.10 2 Days

Proximity sensor

HC­SR04 0.00 2.60 2 Days

General resistors/capacitors

0.00 0.3 2 Days

Microcontroller ATmega328 4.00 1.30 4 2 Days

Signal Amplifier

LA4425A 4.00 2.00 5 5 Days

Motor Coin Vibration Motor

2.00 2.00 5 Days

PCB Oshpark 9.00 3.00 12 Days

Radio Module nRF24L01+ 3.50 1.50 6 2 Days

Enclosure N/A 1 Day

Power Supply LiOn battery 1.25 1.25 2 Days

Power Regulator

MIC5205 4.00 0.75 8 Days

Total 35.75 14.80

4 For Bulk order of 6000 or more 5 For Bulk order of 5000 or more 6 For Bulk order of 1500 or more

Veyebrations 17

Testing strategy Pass Fail Prerequisites Test Description

Engineering requirement Pass condition Type of test

1 The system should not exceed $100. 1

All components total to a cost of <= $100 Acceptance test

2

From when the user points the system at an object to when the system begins to vibrate there should no more than 200ms delay measured. 2

The time taken for the system to propagate from a read distance to setting a vibration rate is under 200ms Acceptance test

3 The system should have 3 buttons/switches or fewer. 3

System has three switches or less Acceptance test

4 Place an object 10 ft from the system at room temperature. 4

System vibrates at speed appropriate for 10 feet Acceptance test

5 Place an object 1 ft from the system at room temperature. 4

System vibrates at speed appropriate for 1 foot Acceptance test

6 Place an object 5 ft from the system at room temperature. 4

System vibrates at speed appropriate for 5 ft Acceptance test

7

Replace system batteries. Place system 5 ft from an object. Turn on system. Wait three hours. 5

System is still powered and functional Acceptance test

4 8 Place an object 10 ft from the system at room temperature. 6

System vibrates at speed appropriate for 10 feet Acceptance test

5 9 Place an object 1 ft from the system at room temperature. 6

System vibrates at speed appropriate for 1 foot Acceptance test

6 10 Place an object 5 ft from the system at room temperature. 6

System vibrates at speed appropriate for 5 ft Acceptance test

16,17 13 The system should function after a drop of 2 meters. 8

System functions properly after the drop of 2 meters Integration test

Veyebrations 18

14

The system should have a switch that disables all functionality of the device. 9 Acceptance test

15 The system should function after a drop of 0.5 meters 8

System functions properly after the drop of 0.5 meters Integration test

15 16 The system should function after a drop of 1 meter 8

System functions properly after the drop of 1 meter Integration test

17

The enclosure should not break after a drop of 2 meters. 8

Enclosure is intact after the drop of 2 meters Unit test

18

The software should be able to set an arbitrary level of vibration 4

Function that sets the vibration of the motor based on an input parameter Unit test

19

The distance sensor should take measurements without interfering with other distance sensors 4

Two sensors in near proximity are both able to validly measure distance Unit test

20

Place thermistor in an environment with temperature of ­20 °C (e.x. a freezer) 6

Thermistor measures ­20 °C ± 5% Unit test

21

Place thermistor in an environment with temperature of 20 °C (Room Temp) 6

Thermistor measures 20 °C ± 5% Unit test

22

Place thermistor in an environment with temperature of 50 °C (e.x. oven) 6

Thermistor measures 50 °C ± 5% Unit test

23

The signal levels expected from the microcontroller should be amplified by the current amplifier sufficiently enough to drive the motor 4

The motor should be able to vibrate within the desired ranges Unit test

24 All systems should function on breadboard

2, 4, 5, 6, 8, 9

All sensor data is valid, microcontroller computations are correct, and vibration speeds are adjusted properly Integration test

25 Software should be able to read sensors for valid data 4,6

Microcontroller receives valid data reads on the distance Unit test

Veyebrations 19

and temperature sensors

26

Visually inspected components on PCB should not be tomb stoned or solder bled 5,8

No components should be sticking inappropriately or unnecessarily soldered to one another Unit test

27

Resistors and capacitors should be verified before applied to the PCB or breadboard

Multimeters should verify components to a 5% tolerance Unit test

28 Code online should include a GPLv2 license file

Repository should contain a file describing the code as being under the GPLv2 license Unit test

29 System should function properly in the enclosure

2, 4, 5, 6, 8, 9

All sensor data is valid, microcontroller computations are correct, and vibration speeds are adjusted properly Integration test

30 Code should compile

The IDE should verify the code compiled successfully Unit test

4,5,6 31

System measures distances [1 ft,10 ft] correctly at low temperatures 6

Distance correctly measured Acceptance test

4,5,6 32

System measures distances [1 ft,10 ft] correctly at high humidity 6

Distance correctly measured Acceptance test

4,5,6 33

System measures distances [1 ft,10 ft] correctly at low humidity 6

Distance correctly measured Acceptance test

34 System dimensions 7

Assembled system has dimensions smaller than 1" x 2" x 3" Acceptance test

Risks PCB risks When working with PCB there are risks that go with the territory. To avoid issues, the

Veyebrations 20

entire design will also be constructed on a breadboard. To do this, all surface mount parts will need complimentary dip mount parts for the breadboard assembly. This means a dip ATmega328 chip will also need to be purchased. This design decision was made to avoid later costs and time constraints with possible assembly errors. It was also made to expedite the testing process. Testing can begin early on the breadboard design and will not need to wait for a final manufactured PCB board.

Manufacturing and shipping time for the PCB board is approximately 12 days from the order being placed OSHpark at a cost of about 5 dollars per square inch. In addition to this a stencil will also need to be purchased for the solder screen. This will likely be bought from OSH Stencils at about 60 cents.

Once ordered and assembled each component should be tested to ensure there is no soldering mishaps. Trace lines should be tested as well to ensure there were no manufacturing errors. Solder bleeding is a likely problem to occur. It is likely a manual soldering job will be required to go in and clean up the reflow oven job. This should be heavily tested to make sure there are no adjoining pins soldered together before the microcontroller is powered up. Another problem is called tomb stoning. A component can stand up vertically and is likely to happen with smaller 2 input components like capacitors and resistors. The solution for this is to remove these components and manually solder them. Another likely problem is a business logic error. Something will be miswired and need to be ran to a different component in some other unthought of way. To avoid this, the breadboarding is absolutely necessary. We will also allocate as much time as necessary to reorder boards if needed.

Enclosure risks 3D printing was the process decided on to design the enclosure. This process is used to mitigate the risks involving the enclosure to ensure that a successful device is created.

There are several risks that are involved with the 3D printing process that needed to be mitigated. The first risk is the cost of the material used in the 3D printing process. The material selected is ABS (Acrylonitrile Butadiene Styrene). A 1kg spool of this type of filament costs $22 which is enough to produce multiple enclosures.

The 3D printer selected also needs to support the necessary dimensions for the product. Our device is small which makes 3D printing an ideal solution. The 3D printers that we will be using will support printing out the dimensions needed and most 3D printers out there will as well.

3D printing also has risks associated with the time it will take to design the enclosure. Since a CAD file design is needed, a technology had to be chosen to mitigate the time needed to design the enclosure. For this, tinkercad was the selected software chosen

Veyebrations 21

to design the enclosure in. This software makes use of quickly laying out shapes to design a component that can quickly be exported as a CAD file.

Finally, the last risk looked at was the actual material selected for printing the enclosure. As stated above, ABS was the chosen material. The properties of this material can be seen in the table below.

ABS (Acrylonitrile / butadiene / styrene) UNITS ASTM# RANGE

Tensile Strength MPa D638 22 Tensile Modulus MPa D638 1627 Flexural Strength MPa D790 41 Flexural Modulus MPa D790 1834 Notched Izod Impact J/m² D256 107 Unnotched Izod Impact J/m² D256 214 Heat Deflection t° °C D648 at 0.45 MPa: 90

at 1.81 MPa: 76 Density g/cm³ 1.05 Elongation at Break % 6 Colors Red, natural steel gray, black, white

This material needs to be durable enough to stand a fall and withstand higher temperatures. In this case, ABS was the best material.

Coordination-related risks The key­passing protocol, which the systems use to ensure only one system in a given area is chirping at any particular time, make assumptions about the behavior of keys that make things easier, but may not be realistic. Mostly in the realm of what happens when two keys enter the same area.

Any system which requires systems to wait and act one­at­a­time will induce lag in the systems. The system has a tight time budget, and this delay may be unacceptable. The maximum time for a round trip, 125 ms , is more than half of the specified reaction time 7

­ two round trips at this timing would violate the requirements.

If it is possible to turn off a system remotely, it is unknown how this link will be kept secure ­ such that one person is not able to turn off another person’s systems either maliciously or accidentally, by say turning off her own systems.

Milestone chart J ­ Joshua Pueschel, R ­ Raymond Dodge, D ­ Dylan Ayrey

# Description Dependencies Original Date

Modified Date Responsibility

7 (2 * MaxRange) ÷ SlowestSpeedOfSound = (2 * 10m) ÷ 318.87 m/s ≈ 0.125 s = 125 ms

Veyebrations 22

0 Purchase components JRD

1 Unit test components to verify functionality ­­ 2015­09­06 ­­

1.1 Unit test thermistor 0.1 2015­09­06 J

1.2 Unit test proximity sensor 0.2 2015­09­06 R

1.3 Unit test amplifier 0.3 2015­09­06 D

1.4 Unit test vibrating motor 0.4 2015­09­06 J

1.5 Unit test atmega328 0.5 2015­09­06 R

1.6 Unit test radio module 0.6 2015­09­06 D

1.7 Unit test

resistors/switches/buttons/capacitors 0.7 2015­09­06 J

1.8 Unit test power regulator 0.8 2015­09­06 D

2 Write software for components ­­ 2015­09­13 ­­

2.1 Write software for temperature control 2015­09­13 J

2.2 Write software for radio communications 2015­09­13 R

2.3 Write software for vibration control 2015­09­13 D

2.4 Write software for proximity detection 2015­09­13 D

3 Write software to integrate components 2.* 2015­09­19 JRD

4 Create mockup on breadboard 0.*, 3.0 2015­09­19 JRD

5 Integration test mockup and revise 3.0, 4.0 2015­09­20 JRD

5.1 Tune vibration control algorithm 5.0 , 2015­09­20 JRD

6 Create PCB board ­­ 2015­09­27 ­­

6.1 Design PCB Schematic 2015­09­27 JRD

6.2 Design PCB Layout 6.1 2015­10­17 JRD

6.3 Order PCB board 6.2 2015­10­11 JRD

7 Create Enclosure ­­ 2015­10­17 ­­

7.1 Design Enclosure 6.2, 1.* 2015­10­17 JRD

7.2 Print Enclosure 7.1 2015­11­07 J

8 Mount components on PCB board ­­ 2015­11­07 ­­

8.1 Mount the surface mount in reflow oven 2015­11­07 JRD

8.2 Cleanup the reflow results 8.1 2015­11­13 JRD

8.3 Mount dip components and non­surface

mount components 8.2 2015­10­24 JRD

9 Test PCB board 8.* 2015­11­11 JRD

Veyebrations 23

10 Integration test for enclosure and PCB board ­­ 2015­11­13 ­­

10.1 Test board fits in enclosure securely 9 2015­11­25 JRD

10.2 Test system functions in enclosure 9 2015­11­25 JRD

11 Acceptance testing ­­ 2015­11­25 ­­

11.1 Drop test 10.* 2015­11­25 JRD

11.2 Comfortability Test 10.* 2015­11­25 JRD

12 Polishing 11.* 2015­11­25 JRD

Prospective All in all the final product came out to something we are all very proud of. There were a few design changes, however most of them made the product better. One example was when we tested for interference and found that two devices would not interfere with one another. This allowed us to remove the RF module and cut down costs, while improving battery life. Another example, is when we changed our distance algorithm. We found through manual testing that distance sensing should not be translated linerally. Even though this goes against our original design, the change made a better product. A few disappointments include not getting the SMD atmega chip to work properly, and not getting the size requirements we originally intended for. Though these were setbacks, it did not destroy the project, and given more time, a product could be brought to market with those conditions satisfied. Another regrettable thing was not getting a visually impaired person to test the system. While we could impair our vision and test the system, it is not quite the same as actually getting a member of the visually impaired community to provide direct feedback. If this product where to go to market this would definitely be a must. Given that the designs are all open source, it is our hope someone can learn from the project, and pick it up someday. One of the main goals was to show existing technologies that do the same task are unnecessarily expensive. This task was achieved far better than any of us could have hoped for, by producing a product that costs less than 20 dollars to manufacture.