Ultrasonic sensors are excellent tools to measure the distance without real contact and are used in various places such as water level measurement, distance measurement, etc. This is an efficient way to measure small distances accurately. In this project we have used an ultrasonic sensor to determine the distance of an obstacle from the sensor. The basic principle of ultrasonic distance measurement is based on ECHO. When sound waves are transmitted in the environment, the waves return to the origin as ECHO after hitting the obstacle. So we just need to calculate the travel time of both sounds means exit time and return time to origin after hitting the obstacle. As the speed of sound is known to us, after some calculation we can calculate the distance.
Components
1. Arduino Pro Mini
2. Ultrasonic sensor module
3. 16x2 LCD
4. Scale
5. Bread board
6. 9-volt battery
7. Cable connection
Ultrasonic Sensor Module
The ultrasonic sensor HC-SR04 is used here to measure the distance in the range of 2cm-400cm with an accuracy of 3mm. The sensor module consists of the ultrasonic transmitter, the receiver and the control circuit. The operating principle of the ultrasonic sensor is as follows:
1. The high level signal is sent for 10us using the trigger.
2. The module sends eight 40 KHz signals automatically and then detects whether or not the pulse is received.
3. If the signal is received, then it is through high level. The high-time time is the time interval between sending and receiving the signal.
Distance = (Time x Speed of sound in air (340 m / s)) / 2
Time diagram
The module works on the natural sound ECHO phenomenon. A pulse is sent for approximately 10 seconds to activate the module. After which the module automatically sends 8 cycles of 40 KHz ultrasound signal and checks its echo. The signal after striking with an obstacle turns back and is captured by the receiver. Thus, the distance from the obstacle to the sensor is calculated simply by the formula given as
Distance = (time x speed) / 2.
Here we have divided the product of speed and time by 2 because time is the total time it took to reach the obstacle and go back. Therefore, the time to reach the obstacle is only half the total time taken.
An automatic ultrasonic braking system to avoid frontal collision with the accelerator pedal disconnect mechanism. This system consists of ultrasonic sensors, namely, ultrasonic wave emitter and ultrasonic wave receiver. The ultrasonic wave emitter is provided at the front of the car, producing and emitting ultrasonic waves at a predetermined distance in front of the car. An ultrasonic wave receiver is also provided in the front portion of the car, receiving the ultrasonic wave signal reflected from the obstacle. The reflected wave (detection pulse) is measured to obtain the distance between the vehicle and the obstacle. The PIC microcontroller is then used to control the servomotor based on detection pulse information, and the servomotor automatically controls the braking of the car. This work demonstrates the possible use of an accelerator pedal decoupling mechanism in this system, whereby the accelerator pedal automatically disengages once the braking is started. Therefore, even if the acceleration pedal is depressed the vehicle will not accelerate and this will avoid collision. This solves the safety problem in case the accelerator pedal is depressed when the vehicle is expected to brake.
Circuit diagram