ME 3484

Integrated Term Project Prototype:

Smart Cane

Group 9: Daniella Bacskay Yahya Khattab

Bumsoo Kim

5/1/03Abstract

The objective is to design a smart cane that will detect different distances of an

approaching object and output a corresponding vibration. This user friendly interface is

equipped with comforting handle, easily installable, and aesthetically appealing. The

user may set the standard detection distance as it may vary for the purpose of beginners,

who are just starting to adjust and become familiar with a cane, to advanced users.

Introduction

The user will be able to recognize how far a specific object is and to thus get

around it. First, the user has to press a button on the cane continuously and then release it

to start the detection process. The detection process will only start operating once at a

standard distance that is defined by that user because if the user is a beginner they may

prefer for precautious reasons to know the distance much a head of time.

The user will have to press for a short period of time and release that button to

recheck the distance and generate the corresponding sounds and vibration again. The user

has the option of pressing that button for a longer period of time and then releasing to

terminate the cane’s operation. To accomplish this, an infrared or ultra-sonic sensor is

placed in front of the cane and also an infared transmitter and receiver is placed at an

angle at the bottom of the cane. For the vibration a 555-CMOS Timer in an astable mode

is used with a brush motor (vibration motor). In addition, if the user forgets or drops the

cane and is unable to find it, the cane will send out a certain sound that will alert that user

of its location, this will be incorporated through a 4-lead pushbutton that will terminate

when the person is continuously holding the cane. The importance of the cane is due to

its physical necessity such as, if there is a pot hole, a sidewalk, or stairs it will allow the

user to beware of that drop or increment.

Background

IR Transmitter with Heat Shrink Tubing:

Figure 1: IR Transmitter with Heat Shrink Tubing

This IR Transmitter with Heat Shrink Tubing is used as an object detection

sensor. The infrared LED transmits a signal that is bounced off an object and then is

received by an infrared receiver. The infrared LED is controlled by frequency; thus,

using BASIC Stamp 2 this is controlled by the FREQOUT command.

Technical Specifications:

Forward voltage: MAX 1.5v

Power Dissipation: 100mW

Continuous forward current: 50mA

Tolerance of: +/- .010 (.25) on all nonnominal dimensions unless otherwise specified.

Operating Temperature: (-40 to +100)◦C

Infrared Receiver:

Figure 2: Infrared Receiver

Infrared can be used to detect the difference between black and white for line

following. Infrared can also be used to determine the distance of an object from the other

object. It can be used to detect and avoid high ledges, and it can use this information to

follow objects at a fixed distance. The infrared detectors send signals to the BASIC

Stamp indicating whether or not they detect infrared reflected off an object. For example,

then the BASIC Stamp, makes decisions and operates the servo motors based on this

input where a stopper will come out informing the physically disabled person to stop.

The IR detectors have built-in optical filters that allow very little light except the

980 nm. infrared that we want to detect onto its internal photodiode sensor. The infrared

detector also has an electronic filter that only allows signals around 38.5 kHz to pass

through. In other words, the detector is only looking for infrared flashed on and off at

38,500 times per second. This prevents interference from common IR interference

sources such as sunlight and indoor lighting. Sunlight is DC interference (0 Hz), and

house lighting tends to flash on and off at either 100 or 120 Hz, depending on the main

power source in the country where you reside. Since120 Hz is way outside the electronic

filter’s 38.5 kHz band pass frequency, it is, for all practical purposes, completely ignored

by the IR detectors.

Devantech SRF04 ultrasonic range finder:

Figure 3: Devantech SRF04 ultrasonic range finder

The Devantech SRF04 ultrasonic range finder provides precise, non-contact

distance measurements from about 3 cm (1.2 inches) to 3 meters (3.3 yards). It is very

easy to connect to BASIC Stamps or the Javelin, requiring only two I/O pins. The SRF04

works by transmitting an ultrasonic (well above human hearing range) pulse and

measuring the time it takes to "hear" the pulse echo. Output from the SRF04 is in the

form of a variable-width pulse that corresponds to the distance to the target.

Requirements and Capabilities:

• Voltage – 5V

• Current - 30mA Typ. 50mA Max.

• Frequency - 40KHz

• Max Range - 3 m

• Min Range - 3 cm

• Sensitivity - Detect 3cm diameter broom handle at > 2 m

• Input Trigger - 10uS Min. TTL level pulse

• Echo Pulse - Positive TTL level signal, width proportional to range.

• Small Size – (1.7 in x .8 in x .7 in height) 43mm x 20mm x 17mm height

The SRF04 detects objects by emitting a short burst of sound and "listening" for

the echo. Under control of the BASIC Stamp, the SRF04 emits an ultrasonic (40 kHz)

sound pulse. This pulse travels through the air at about 1.1 feet per millisecond (the speed

of sound), hits an object and then bounces back. By measuring the time between the

transmission of the pulse and the echo return, the distance to the object can be

determined.

The SRF04 outputs a high-going pulse that corresponds to time required for the

echo to return. PULSIN can be used to measure it and determine the distance to the

target. There's a convenient side-effect with PULSIN on the BASIC Stamp 2: the value

returned for the round-trip is in two microsecond units – the same as a one-way trip

(sensor to target) in one microsecond units. The trigger pulse must be at least 10

microseconds long. PULSOUT can do this for us. The other requirement is that we must

wait 10 milliseconds between measurements.

Frequency Range of Hearing for Humans and Selected Animals: Animal Frequency (hertz) Low High

Humans 20 20,000 Cats 100 32,000 Dogs 40 46,000 Horses 31 40,000 Elephants 16 12,000 Cattle 16 40,000 Bats 1,000 150,000 Grasshoppers and locusts 100 50,000 Rodents 1,000 100,000 Whales and dolphins 70 150,000 Seals and sea lions 200 55,000 Reference: Encyclopedia Britannica

Sonar is a system in which objects are detected by sound waves. These waves are

very high in frequency and are called ultrasonic. Ultrasound waves have frequencies

above 20 kHz. Few animals can hear ultrasonic waves. Some of the animals that can hear

them are dogs, cats, porpoises, rodents, whales, dolphins, seals, sea lions and bats. The

Ultrasonic Dog Chaser produces a discomforting, but not harmful, high frequency sound,

audible to dogs but not to humans. The frequency range is 20,000 Hz - 25,000 Hz, the

intensity is 135 dB and the effective range is within 20 feet. Although the dogs may hear

the sounds that we cannot hear, they may not respond adversely to them. However they

would only do so if the decibel value was high enough to hurt them.

Capacitor:

A capacitor is a passive electronic component that stores energy in the form of an

electrostatic field. In its simplest form, a capacitor consists of two conducting plates

separated by an insulating material called the dielectric. The capacitance is directly

proportional to the surface areas of the plates, and is inversely proportional to the

separation between the plates. Capacitance also depends on the dielectric constant of the

substance separating the plates. The standard unit of capacitance is the farad, abbreviated

as F. This is a large unit; more common units are the microfarad, abbreviated µF, pF.

Capacitors can be fabricated onto integrated circuit (IC) chips.

They are commonly used in conjunction with transistors in dynamic random

access memory (DRAM). The capacitors help maintain the contents of memory. Because

of their tiny physical size, these components have low capacitance. They must be

recharged thousands of times per second or the DRAM will lose its data. Large capacitors

are used in the power supplies of electronic equipment of all types, including computers

and their peripherals. In these systems, the capacitors smooth out the rectified utility AC,

providing pure, battery-like DC.

DC motor:

A DC motor is an electromechanical device in which an electrical input

determines the speed and the direction of the rotation. DC motors are used extensively in

various applications such as robotics, security doors and vending machines.

Figure 4: DC motor

The DC motor can be controlled in many ways and has many technical

considerations. Depending on the voltage provided to the motor it will either run faster

or slower. There are many ways to control the rate of rotation, but the way that it was

implemented was to use a potentiometer and a 555-timer. The 555-timer gives out on

and off pulses to the DC motor. These pulses are dependent on the resistance value

which is changed by the digital potentiometer.

Resistor:

A resistor is an electrical component that limits or regulates the flow of electrical

current in an electronic circuit. Resistors can also be used to provide a specific voltage for

an active device such as a transistor. All other factors being equal, in a direct-current

(DC) circuit, the current through a resistor is inversely proportional to its resistance, and

directly proportional to the voltage across it.

This is the well-known Ohm's Law. In alternating-current (AC) circuits, this rule

also applies as long as the resistor does not contain inductance or capacitance. A resistor

is a component that has electrical resistance and that is used to control the flow of current

in an electronic circuit.

BASIC Stamp 2 Module:

Figure 5: BASIC Stamp 2 Module

This module normally has no shortage of program space or I/O pins. Serial PC

interface provides enhanced debug features. The BS2-IC is recommended for first-time

BASIC Stamp users because of the many resources, documentation, source code, and

customer projects that are available for the BS2-IC. A PIC-based PBASIC interpreter is

used.

Board of Education:

Figure 6: Board of Education

This Board of Education requires the use of a BASIC Stamp 2. This Board of Education

is used to teach microcontroller programming and interfacing. Mechanically interlocked

power supply to prevent dual connection of wall-pack and 9-volt battery; DB9 connector

for BS2-IC programming and serial communication during run-time; P0 - P15 I/O pins,

Vdd and Vss connections brought adjacent to 5.1 x 3.5 cm (2" x 1 3/8") breadboard area;

Includes set of ten (10) color-coded 22 gauge wires; Female 10-pin dual row connector

for optional AppMods (more breadboard space); Traces on top of the board show

connections between BS2-IC and breadboard connections; and #28150 does not include a

BS2-IC or power supply.

Equipment

IR Transmitter with heat shrink tubing and Infrared Receiver

Devantech SRF04 Ultrasonic Range Finder

BASIC Stamp Editor program

BASIC Stamp II

Board of Education

Programming cable

Transistor

Diode

Two 4-Lead Pushbuttons (Tact Switch)

ZH1531 A Brush Motor (vibration motor)

Parallax Servomotor

Stopper (soft wire hits leg informing a need to stop)

CMOS 555 Timer (NE 555N)

DS1804-100 (100K) Solid State Potentiometer

100 ohm, ¼ watt resistors (brown, black, brown)

100 picoF and Two 0.22 F Capacitors

9 Volt battery or wall transformer

Connecting wires

Cane

Diagrams of Circuit

Figure 1: Physical Picture for Electrical Circuit Setup (IR receiver and transmitter)

Figure 2: Schematic Diagram

Cost Analysis

Items CostIR Transmitter with heat shrink tubing $5.20

Infrared Receiver $2.60

Devantech SRF04 Ultrasonic Range Finder $32.95

Board of Education & BS2 $100.00

9V Battery + AA battery $5.50

ZH15431 brush motor (vibration motor) $2.50

Cane $15.00

Mosfet IRF510 $1.99

SI Diode IN4001 $0.95

NE555 CMOS Timer $2.00

DS1804 -100K $4.00

Box $2.00

Miscellaneous $10.00

Total

Cost Analysis for Mass Production $50-70

Program:

'{$STAMP BS2}x var word 'for the motorsy var wordn var wordoutput 10low 10input 14input 15

clik0: ' loop here while the button is upif in14=1 then clik0 ' decide if it is up(1) or down(0)goto mainn=0 ' zero the timer

clik: ' loop here while the button is upif in15=0 then clik0pause 5000if in14=1 then drop ' decide if it is up(1) or down(0)n=0 ' zero the timer

clik1: ' loop here while the button is downn=n+1 ' increment the timer

if n=500 then longclik ' branch out if it reaches 500if in15=0 then clik0 ' or loop until the button goes back up(1)

main: '------------------infrared--------------------------------IR_det VAR bit 'bit variable for saving IR

'InitializationOUTPUT 12 'Set I/O pin 7 to an output

'Main RoutineFREQOUT 12, 1, 38500 'Send a freqout signalIR_det = IN13 'store IR detector outputDEBUG home, bin1 IR_det,crPAUSE 20

if IR_det=0 then normal 'if you detect stairs then play a falling freqout 7,50,3800 sound, 0 means stairsfreqout 7,50,2533freqout 7,50,1900

normal:n=0 ' r rezero the time

'------------------sonar sensor-----------------------------wDist var wordINT con 0ECHO con 1

convfac con 74

main_sonar:pulsout INT, 5output INTrctime ECHO, 1, wDistwDist = wDist/convfacpause 10debug dec wDist, crif wDist<24 then motor1if wDist<36 then motor2if wDist<48 then motor3

if in14=1 then clikgoto clik0

'------------------motor levels-----------------------------

motor1:

output 10 '555 timer on/offoutput 4 'up/downoutput 5 'incrementoutput 3 ' chip select

high 10low 3low 4

for x = 1 to 99high 5low 5next

high 4

for y = 1 to 1high 5low 5next

goto here'--------------------------------motor2---------------------motor2:

output 10 '555 timer on/offoutput 4 'up/downoutput 5 'incrementoutput 3 ' chip select

high 10low 3low 4

for x = 1 to 99high 5low 5next

high 4

for y = 1 to 30high 5low 5next

goto here

'------------------------motor3-----------------------------motor3:

output 10 '555 timer on/offoutput 4 'up/downoutput 5 'incrementoutput 3 ' chip select

high 10low 3low 4

for x = 1 to 99high 5low 5next

high 4

for y = 1 to 65high 5low 5next

goto here

'-----------------------------------------------------------

drop: ' if user drops cane ' r loop until the button goes back upfreqout 7,50,3800 ' r play a unique falling soundfreqout 7,50,2533freqout 7,50,1900if in15=0 then clik0if in14=1 then dropgoto clik0 ' r back to the top

here:low 10 'infinite loop'if in15=0 then clikif in14=1 then clikgoto clik0

longclik: ' come here if pushbutton is held down.freqout 7,5,3800,2533 ' r play a chirp in a loop

if in15=0 then longclik ' r loop here until the button goes back upgoto clik ' back to the top

Conclusion

Smart Sensors are not just a fad, they are the wave of the future. As more people

realize the value of these inventions the field will grow without bounds. This can be

demonstrated by the design specified. It’s practical, cost efficient and extremely useful.

If all of these characteristics weren’t enough to warrant investigation into this field of

study, these inventions will also make the inventor very wealthy.

Reference

1. “What is a Microcontroller”, http://www.parallax.com/Downloads/Documentation/edu/What's_a_Microcontroller.pdf

2. “Earth Measurements”, http://www.parallax.com/Downloads/Documentation/edu/Earth_Measurements.pdf

3. “Robotics”http://www.parallax.com/Downloads/Documentation/edu/Robotics.pdf

4. “Motor selection”, http://www.robotroom.com/TinyMotor.html

5. “Ultrasonic applications”, http://hypertextbook.com/facts/1998/JuanCancel.shtml