HC-Sr04 ultasonic sensor for obstacle detection.

why don't u use a single ultrasonic sensors with serial output available in market,this will also reduce cost of 3 extra sensors.By doing simple rotating assembly u can detect objects around .

gaurav7577

Thank you for your comment. well using a single sensor by using a rotating assembly seems a nice idea but i am not really sure if it will be efficient. first things first where to place the rotating assembly? if it is place under the wheel chair then it will detect its own wheels. If place on top then it might not detect the smaller objects on any side. I see only these two options for the placement of rotating assembly.

Thank you every one for your valued comments.
I am really sorry.I think that i was unable to state my problem in my first thread post.
The problem i am facing at the moment is that i have already got the HC-SR04 sensors (which are really costly in my country.By the way i am from Nepal)
so i have no choice then to go on with using these sensors. And what i am really confused about is how to connect these sensors such that i can use the output from the echo pins to program the correct movement or adjustments that are to be made to avoid the obstacles.
I have read many post online which use one sensor to display the distance at which a object is place.
I was trying to say that i do not need to display the distance but set a predefined distance between the wheelchair and the object in the program so that if there is a object in front of the chair then it slows down and stops its self and if it detects any objects on the sides then it can prevent the chair from collison.
For example the disabled person saw an obstacle in the front the sensors stopped the chair and now the person gave a command to turn right and there is a object on the right side also then the sensors on the right side would prevent the chair from turning towards the right also. Well this is my concept for using the sensors in all the sides.
What i am asking here is a guide line to connect and program these multiple number of sensors and obtain the output in different I/O pins to use them as signals for program execution

What i am asking here is a guide line to connect and program these multiple number of sensors and obtain the output in different I/O pins to use them as signals for program execution

Wrosun

Basically you use the sensors one at a time.
Each has its own trigger signal,one per micro controller pin.
All four HC-SR04 echo pins then need to be 'mixed' to connect to a single interrupt pin.
A CD4066 could be used as a multiplexer and there are other ways.
Pulse a sensor, select it as input(through the CD4066) measure the distance..do next.

I was trying to say that i do not need to display the distance but set a predefined distance between the wheelchair and the object in the program so that if there is a object in front of the chair then it slows down and stops its self and if it detects any

Any code that that does distance measurement starts by operating the HC-SR04
and getting a number to represent the distance.
Use the code up to that point and throw away the rest of it
Simply compare the distance number to the limit you set.

You can use the similar code that was mentioned in the parallax ping sensor thread.