HC-Sr04 ultasonic sensor for obstacle detection.

Hello!
I am doing a project titled "Voice Controlled Wheel Chair"
HM-2007 ic is used for voice recognition and according to the output from the ic the wheel chair will move.
The microcontroller used will be AT89S52.
In addition to voice control i am thinking of adding ultrasonic sensors in the wheel chair so that the disabled person will get assistance in their movement.
I have thought of putting one ultrasonic sensro in the front,one at the back , one at the right side and one on the left side (i.e one on every side).
Now the problem is that i dont know how to interface multiple ultrasonic sensors with the microcontroller.
I have read the "Pulse generator using p89c51rd2" thread and it is mainly for distance measurement.
In my case there is no necessity to measure the distance it is ok if the sensor detects the obstacle when it is far enough such that it might give alert to the person using the wheel chair.
thank you.

The thread you've referred is for parallax ping sensor which is specifically designed to measure distance but can also be used for obstacle detection. There is a lot of circuitry involved in designing ultrasonic sensor. I would not prefer making your own ultrasonic sensor design. HC-SR04 is a good sensor and its similar to that of parallax ping. Even if you don't want to measure distance but you can still use it for obstacle detection.

I'm not really sure how the sensors will help ?
Generally disabled people can see what is around them.

Maybe he is trying to target blind + disabled?

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 .

I'm not really sure how the sensors will help ?
Generally disabled people can see what is around them.

ExperimenterUK

Okay..
Automatic stop is a good idea for a voice controlled system.
Perhaps just front and back though.
If you use distance measurement, the chair could slow down as the obstruction
gets nearer.

I like Phil's idea.. Slow down as you get closer to abstacle. You can even notify user with voice prompt saying obstacle ahead at distance of 4ft.

The thread you've referred is for parallax ping sensor which is specifically designed to measure distance but can also be used for obstacle detection. There is a lot of circuitry involved in designing ultrasonic sensor. I would not prefer making your own ultrasonic sensor design. HC-SR04 is a good sensor and its similar to that of parallax ping. Even if you don't want to measure distance but you can still use it for obstacle detection.

Ajay Bhargav

Mr. Ajay Bhargav
I am not thinking of making my own ultrasonic sensors.i want to use HC-SR04 sensors.
I read the post on how to use HC-sr04 sensors and all of them use the int0 and int1 to control the trig and echo pins.
I understood that part.Now where i need help is how to program for more then one HC-SR04 sensors.

I'm not really sure how the sensors will help ?
Generally disabled people can see what is around them.

ExperimenterUK

I agree disabled people can see what is around them but since it is a voice controlled wheel chair and we are trying to give the person a means to control the chair without touching the wheels of the chair (In some cases the person might not have hands to do so). Now another point is that when they use the wheel chair they can be in any kind of environment ....the obstacles they face might be infront or back or either of the two sides(i.e left or right).So providing a extra security is always good.

I'm not really sure how the sensors will help ?
Generally disabled people can see what is around them.

ExperimenterUK

Okay..
Automatic stop is a good idea for a voice controlled system.
Perhaps just front and back though.
If you use distance measurement, the chair could slow down as the obstruction
gets nearer.

ExperimenterUK

yes that is what i really intend to do. I am asking help for the part where i need to interface the ultrasonic sensors to the microcontroller. I would like to differ to you on just using two sensors on the front and back
only. There can be many cases which i have studied
1. The user is moving in a straight path and suddenly something approaches from the sides.
2. The walls on the side might not always be straight,they might also be curved eg: curved hall ways or corridors .
3. And also the sensors on the side will be usefull to maintain a straight path.

I am really confused on how to interface more then one Ultrasonic sensor.