The ultrasonic range finder is based on measuring the time elapsed between emission and returning the echo. When the ultrasonic wave is emitted it spreads with speed of sound in the surrounding air, to 342 m / sec. Once an obstacle is encountered, the echo returns to the transducer which then calculates the elapsed time between transmission and receiving of the wave. These waves can not be heard by the human ear.

All rangefinders work the same way, regardless of the manufacturer. The differences will be within the frequencies transmitted, and the conical diffraction of the wave. Depending on the model, the ultrasonic sensors will be more or less accurate, and will have a greater or lesser extent. Their prices vary accordingly. Generally, the higher is the connical end, the sensor will be more precise, it will be more expensive. But as we shall see, some manufacturers have things differently

This is the application report from Texas Instruments about distance measurement using ultrasonic and MSP430 microcontroller. The report is provided in PDF file, you may download the application report at the end of this post.

This application report describes a distance-measuring system determined by ultrasonic sound using the MSP430F413 ultralow-power microcontroller. The system transmits a burst of ultrasonic sound waves towards the subject point and after that receives the corresponding echo.

This application is primarily based upon the reflection of sound waves. Sound waves are defined as longitudinal pressure waves in the medium in which they’re travelling. Subjects whose dimensions are greater than the wavelength of the impinging sound waves reflect them; the reflected waves are known as the echo. In the event the speed of sound in the medium is recognized and the time taken for the sound waves to travel the distance from the source towards the subject point and back to the source is measured, the distance from the source to the subject point will be computed accurately.

The devices applied to transmit and receive the ultrasonic sound waves within this application are 40-kHz ceramic ultrasonic transducers. The MSP430 drives the transmitter transducer using a 12-cycle burst of 40-kHz square-wave signal derived from the crystal oscillator, and therefore the receiver transducer receives the echo. The Timer_A in the MSP430 is configured to count the 40-kHz crystal frequency such that the time measurement resolution is 25 µs, that is more than enough for this application. The measurement time base is extremely stable because it is derived from a quartz-crystal oscillator. The echo received by the receiver transducer is boosted by an operational amplifier and the amplified output is fed towards the Comparator_A input. The Comparator_A senses the presence of the echo signal at its input and triggers a capture of Timer_A count value to capture compare register CCR1.

The capture is accomplished exactly at the immediate the echo arrives at the system. The captured count will be the measure of the time taken for the ultrasonic burst to travel the distance from the system to the subject point and back to the system. The distance in inches from the system towards the subject point is computed by the MSP430 implementing this measured time and displayed on a two-digit static LCD. Instantly right after updating the display screen, the MSP430 goes to LPM3 sleep mode to keep electrical power. The Basic Timer1 is programmed to interrupt the MSP430 every 205 milliseconds. The interrupt signal from the Basic Timer1 wakes up the MSP430 to repeat the measurement cycle and update the display screen.

Download the application report of distance measurement using ultrasonic and MSP430 microcontroller
» Download Link 1 (direct download from Texas Instruments)
» Download Link 1 (mirror download)

Arduino Tutorial: Use a Piezo Element to Detect Vibration. This tutorial shows you how to use a Piezo element to detect vibration, in this case, a knock on a door, table, or other solid surface.

A piezo is an electronic device that generates a voltage when it’s physically deformed by a vibration, sound wave, or mechanical strain. Similarly, when you put a voltage across a piezo, it vibrates and creates a tone. Piezos can be used both to play tones and to detect tones.

The sketch reads the piezos output using the analogRead() command, encoding the voltage range from 0 to 5 volts to a numerical range from 0 to 1023 in a process referred to as analog-to-digital conversion, or ADC.

If the sensors output is stronger than a certain threshold, your Arduino will send the string “Knock!” to the computer over the serial port.

Open the serial monitor to see this text.

Hardware Required

• Arduino Board
• (1) Piezo electric disc
• (1) Megohm resistor
• solid surface

Piezos are polarized, meaning that voltage passes through them (or out of them) in a specific direction. Connect the black wire (the lower voltage) to ground and the red wire (the higher voltage) to analog pin 0. Additionally, connect a 1-megohm resistor in parallel to the Piezo element to limit the voltage and current produced by the piezo and to protect the analog input.

It is possible to acquire piezo elements without a plastic housing. These will look like a metallic disc, and are easier to use as input sensors. PIezo sensors work best when firmly pressed against, taped, or glued their sensing surface.

Schematic Diagram:

A Piezo to attached to analog pin 0 with a 1-Megohm resistor

Code

In the code below, the incoming piezo data is compared to a threshold value set by the user. Try raising or lowering this value to increase your sensor’s overall sensitivity.

/* Knock Sensor
This sketch reads a piezo element to detect a knocking sound.
It reads an analog pin and compares the result to a set threshold.
If the result is greater than the threshold, it writes
“knock” to the serial port, and toggles the LED on pin 13.
The circuit:
* + connection of the piezo attached to analog in 0
* – connection of the piezo attached to ground
* 1-megohm resistor attached from analog in 0 to ground

http://www.arduino.cc/en/Tutorial/Knock

created 25 Mar 2007
by David Cuartielles
modified 4 Sep 2010
by Tom Igoe
This example code is in the public domain.
*/
// these constants won’t change:
const int ledPin = 13; // led connected to digital pin 13
const int knockSensor = A0; // the piezo is connected to analog pin 0
const int threshold = 100; // threshold value to decide when the detected sound is a knock
or not
// these variables will change:
int sensorReading = 0; // variable to store the value read from the sensor pin
int ledState = LOW; // variable used to store the last LED status, to toggle the light
void setup() {
pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT
Serial.begin(9600); // use the serial port
}
void loop()
// read the sensor and store it in the variable sensorReading:
sensorReading = analogRead(knockSensor);
// if the sensor reading is greater than the threshold:
if (sensorReading >= threshold) {
// toggle the status of the ledPin:
ledState = !ledState;
// update the LED pin itself:
digitalWrite(ledPin, ledState);
// send the string “Knock!” back to the computer, followed by newline
Serial.println(“Knock!”);
}
delay(100); // delay to avoid overloading the serial port buffer
}

Download the Arduino Tutorial: Use a Piezo Element to Detect Vibration in PDF document:
» Download Link

Download the document of step by step Make a Robot tutorial:
Download Link

Go to online page of how to make a robot:
Visit the page

This line follower robot use the following module:

• Proximity sensor: 8 pcs of phototransistors
• Microcontroller: ATMega16
• Motor driver: L298 module
• Programming language: C

Download the document of this line follower robot tutorial HERE

This tutorial created by:
Priyank Patil
Department of Information Technology
K. J. Somaiya College of Engineering
Mumbai, India

Lecture 2. Technologies in Robots

Lecture 3. Industrial Robots

Lecture 4. Industrial Manipulators and its Kinematics

Lecture 5. Parallel Manipulators

Lecture 6. Grippers Manipulators

Lecture 7. Electric Actuators

Lecture 8. Actuators – Electric, Hydraulic, Pneumatic

Lecture 9. Internal State Sensors

Lecture 10. Internal State Sensors

Lecture 11. External State Sensors

Lecture 12. Trajectory planning

Lecture 13. Trajectory Planning

Lecture 14. Trajectory Planning

Lecture 15. Trajectory Planning

Lecture 16. Trajectory Planning

Lecture 17. Trajectory Planning

Lecture 18. Trajectory Planning

Lecture 19. Trajectory Planning

Lecture 20. Forward Position Control

Lecture 21. Inverse Problem

Lecture 22. Velocity Analysis

Lecture 23. Velocity Analysis

Lecture 24. Dynamic Analysis

Lecture 25. Image Processing

Lecture 26. Image Processing

Lecture 27. Image Processing

Lecture 28. Image Processing

Lecture 29. Image Processing

Lecture 30. Image Processing

Lecture 31. Robot Dynamics and Control

Lecture 32. Robot Dynamics and Control

Lecture 33. Robot Dynamics and Control

Lecture 34. Robot Dynamics and Control

Lecture 35. Robot Dynamics and Control

Lecture 36. Robot Dynamics and Control

Lecture 37. Futuristic Topics in Robotics

Lecture 38.

Lecture 39.

Lecture 40. Futuristic Topics in Robotics

I’ve collected some schematic diagrams of sound activation as follow:

Sound Activation schematic 1

Sound Activation schematic 2

Sound Activation schematic 3

Sound Activation 4 schematic

Sound Activation schematic 5

You may see the video here.

This line follower robot is very small and simple. This robot is running fast and follow the line very smoothly.

Mechanics

All mechanical and electrical parts are mounted on a proto board, and it also constitutes the chasis.

The line following robot is upheld in three points of two driving wheels and a free wheel. The driving wheels are made with a 7 mm dia ball bearing and a rubber tire. The free wheel is a 5 mm dia ball bearing attached loosely. To drive driving wheels, two tiny vibration motors that used for cellular phone, pager or any mobile equipment are used. Its shaft is pressed onto the tire with a spring plate, the output torque is transferred to the wheels.

The steearing mechanism is realized in differential drive that steear the robot by difference in rotation speed between the left wheel and the right wheel. It does not require any additional actuator, only controling the wheel speed will do.

Line detector and Photo reflector

To detect a line to be followed, most contestants are using two or more number of poto-reflectors. Its output current that proportional to reflection rate of the floor is converted to voltage with a resister and tested it if the line is detected or not. However the threshold voltage cannot be fixed to any level because optical current by ambent light is added to the output current like the image shown right.

Most photo-detecting modules for industrial use are using modurated light to avoid interference by the ambient light. The detected signal is filtered with a band pass filter and disused signals are filtered out. Therefore only the modurated signal from the light emitter can be detected. Of course the detector must not be saturated by ambient light, this is effective when the detector is working in linear region.

In this project, pulsed light is used to cancel ambient light. This is suitable for arraied sensors that scanned in sequence to avoid interference from next sensor. The microcontroller starts to scan the sensor status, sample an output voltage, turn on LED and sample again the output voltage. The difference between the two samples is the optical current by LED, output voltage by the ambient light is canceled. The other sensors are also scanned the same avobe in sequence.

Line Detection Signal Processing

Right image shows the actual line posisiton vs detected line position in center value of 640. The microcontroller scans six sensors and calcurates the line position by output ratio of two sensors near the line. Thus the line position can be detected lineary with only six sensors. All the sensor outputs are captured as analog value that proportioning to reflection ratio, and the sensitivity have variety between each one of them. In this system, to remove the variations from the outputs, calibration parameters for each sensor can be held into non-volatile memory. This can be done with online mode. The microcontroler enters the online mode when an ISP cable is attached, and it can be controlled with a terminal program in serial format of N81 38.4kbps. S1 command monitors sensor values, and S2 command calibrates variation of sensor gain on the reference surface (white paper). The ATmega8 must be set to 8MHz internal osc.

Tracking Control

The line position is compeared to the center value to be tracked, the position error is processed with Proportional/Integral/Diffence filters to generate steering command. The line folloing robot tracks the line in PID control that the most popular argolithm for servo control.

The proportional term is the commom process in the servo system. It is only a gain amplifire without time dependent process. The differencial term is applied in order to improve the responce to disturbance, and it also compensate phase lag at the controled object. The D term will be required in most case to stabilize tracking motion. The I term is not used in this project from following resons. The I term that boosts DC gain is applied in order to remove left offset error, however, it often decrease servo stability due to its phase lag. The line following operation can ignore such tracking offset so that the I term is not required.

When any line sensing error has occured for a time due to getting out of line or end of line, the motors are stopped and the microcontroller enters sleep state of zero power consumption.
Notes:

• Development diary [Ja]
• Circuit diagram
• Firmware May 23, 2004
• Following motion with only P control
  This is a video file of line following motion with only P control. The servo system oscllated.
• Following motion with P and D controls
  Adding D control could improve the servo stability. The robot follows the line correctly. Therefore the servo parameter must be optimized for mechanical characterristics to improve the tracking stability.

Ho it can be..?
There are many robot tutorial has been written and published through blog or web. I found interesting robot tutorial from this web. The author said that he build the robot just in 2 hours, you also can see the video there… just visit the web…

Another Line Follower Robot without microcontroller project. This project built using IC timer 555 to generated PWM signal to make the motor running smoothly. This Line Follower Robot tutorial written by Jaseung Ku – 17 Dec 2005. May be this is “not professional” robot, but i think it so cool to create a robot simple things around your place.

You can download the tutorial here