Whoa! This project seems really interesting and many of you will agree after reading the post. All the people are familiar with ultrasonic sensor. There are some cheaply available sensor that comes in less than 10$ while some are costly but provides greater range. Why buy a readymade sensor, when you can make your own at a low cost and a considerable range. In an ultrasonic sensor, a short ultrasonic wave is shot out which gets reflected back from the object, and the time after it’s received is noted down. Since we have the time and the speed of ultrasonic we can easily find the distance.
In the design, there is a separate transducer for transmitter and receiver to avoid complexity. He used a 24KHZ transducer which are readymade and are really cheap and with proper tuning you can get considerable range keeping the cost in mind. The ultrasonic transmitter is powered from ATmega328′s counter 1 PWM output (chip pin 16 and Arduino digital pin 10). In order to achieve the maximum output power of the transducer for a given supply voltage, he has used the bridged output design which gives around double the voltage supplied