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Transcript
ME 3484 Integrated Term Project Prototype: Smart Cane Group 9: Daniella Bacskay Yahya Khattab Bumsoo Kim 5/1/03 Abstract 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 Humans Cats Frequency (hertz) Low High 20 100 20,000 32,000 Dogs Horses Elephants Cattle Bats Grasshoppers and locusts Rodents Whales and dolphins Seals and sea lions 40 31 16 16 1,000 100 1,000 70 200 46,000 40,000 12,000 40,000 150,000 50,000 100,000 150,000 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 IR Transmitter with heat shrink tubing Infrared Receiver Devantech SRF04 Ultrasonic Range Finder Board of Education & BS2 9V Battery + AA battery ZH15431 brush motor (vibration motor) Cost $5.20 $2.60 $32.95 $100.00 $5.50 $2.50 $15.00 $1.99 $0.95 $2.00 $4.00 $2.00 $10.00 Cane Mosfet IRF510 SI Diode IN4001 NE555 CMOS Timer DS1804 -100K Box Miscellaneous Total Cost Analysis for Mass Production $50-70 Program: '{$STAMP BS2} x var word y var word n var word output 10 low 10 input 14 input 15 'for the motors clik0: is up if in14=1 then clik0 down(0) goto main n=0 ' loop here while the button clik: is up if in15=0 then clik0 pause 5000 if in14=1 then drop down(0) n=0 ' loop here while the button clik1: is down n=n+1 ' loop here while the button ' decide if it is up(1) or ' zero the timer ' decide if it is up(1) or ' zero the timer ' increment the timer if n=500 then longclik reaches 500 if in15=0 then clik0 goes back up(1) ' branch out if it ' or loop until the button main: '------------------infrared-------------------------------IR_det VAR bit 'bit variable for saving IR 'Initialization OUTPUT 12 'Set I/O pin 7 to an output FREQOUT 12, 1, 38500 signal IR_det = IN13 output DEBUG home, bin1 IR_det,cr PAUSE 20 'Main Routine 'Send a freqout 'store IR detector if IR_det=0 then normal 'if you detect stairs then play a falling freqout 7,50,3800 sound, 0 means stairs freqout 7,50,2533 freqout 7,50,1900 normal: n=0 ' r rezero the time '------------------sonar sensor----------------------------wDist var word INT con 0 ECHO con 1 convfac con 74 main_sonar: pulsout INT, 5 output INT rctime ECHO, 1, wDist wDist = wDist/convfac pause 10 debug dec wDist, cr if wDist<24 then motor1 if wDist<36 then motor2 if wDist<48 then motor3 if in14=1 then clik goto clik0 '------------------motor levels----------------------------- motor1: output output output output 10 4 5 3 '555 timer on/off 'up/down 'increment ' chip select high 10 low 3 low 4 for x = 1 to 99 high 5 low 5 next high 4 for y = 1 to 1 high 5 low 5 next goto here '--------------------------------motor2--------------------motor2: output output output output 10 4 5 3 '555 timer on/off 'up/down 'increment ' chip select high 10 low 3 low 4 for x = 1 to 99 high 5 low 5 next high 4 for y = 1 to 30 high 5 low 5 next goto here '------------------------motor3----------------------------motor3: output output output output 10 4 5 3 '555 timer on/off 'up/down 'increment ' chip select high 10 low 3 low 4 for x = 1 to 99 high 5 low 5 next high 4 for y = 1 to 65 high 5 low 5 next goto here '----------------------------------------------------------drop: goes back up freqout 7,50,3800 sound freqout 7,50,2533 freqout 7,50,1900 if in15=0 then clik0 if in14=1 then drop goto clik0 ' if user drops cane ' r loop until the button ' r play a unique falling ' r back to the top here: low 10 'infinite loop 'if in15=0 then clik if in14=1 then clik goto clik0 longclik: pushbutton is held down. freqout 7,5,3800,2533 chirp in a loop ' come here if ' r play a if in15=0 then longclik the button goes back up goto clik ' r loop here until ' 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