About interfacing single or multiple USS(ultra sonic sensor) to arduino board

Using Arduino Project Guidance
1

Hi i am connecting three ultra sonic sensors(MB 1261) to arduino board of three analog pins(A0,A4 and A7) and trigger pin to digital pin 2.The values are fluctuating more for the same obstacle position and also some random values are coming in serial monitor after disconnecting sensor from the analog pin.So can you please help me out in this.Please find below my source code:

/Feel free to use this code.
Author: Tom Bonar
Date: 12-11-2013
Analog pin 1 for reading in the analog voltage from the MaxSonar device.
This variable is a constant because the pin will not change throughout execution of this code./

const int triggerPin = 2;
long anVolt1, anVolt2,anVolt3,anVolt4,sensor1,sensor2,sensor3,sensor4;
long anVolt5,sensor5;

void setup() {
//This opens up a serial connection to shoot the results back to the PC console
Serial.begin(9600);
pinMode(triggerPin,OUTPUT);
delay(200); //Gives time for the sensors to boot and calibrate
}

void start_sensor(){
digitalWrite(triggerPin,HIGH);
delay(200);
//delayMicroseconds(20);
digitalWrite(triggerPin,LOW);
}

void read_sensor(){
//Used to read in the analog voltage output that is being sent by the XL-MaxSonar device.
//Scale factor is (Vcc/1024) per 2 centimeter. A 5V supply yields ~4.9mV/2 cm for long range sensors
anVolt1 = analogRead(A0);
anVolt2 = analogRead(A4);
anVolt3 = analogRead(A7);
/anVolt4 = analogRead(A3);
anVolt5 = analogRead(A4);/
sensor1 = anVolt12;
sensor2 = anVolt22;
sensor3 = anVolt32;
/sensor4 = anVolt42;
sensor5 = anVolt52;*/
}

void printall() {
//Serial.print(anVolt1);
//Serial.print(",");
Serial.print(sensor1);
Serial.print(",");
Serial.print(sensor2);
Serial.print(",");
Serial.print(sensor3);
/* Serial.print(",");
Serial.print(sensor4);
Serial.print(",");
Serial.print(sensor5);*/
Serial.println();
}

void loop () {
start_sensor();
read_sensor();
printall();
delay(300); // This delay time changes by 100 for every sensor in the chain. For 4 sensors this will be 400
}

2

Analog pin 1 for reading in the analog voltage from the MaxSonar device.

You don't appear to read from pin 1

some random values are coming in serial monitor after disconnecting sensor from the analog pin.

So?
What did you expect?

Please remember to use code tags when posting code

3

The values are fluctuating more for the same obstacle position

More than what?

If you mean "values are fluctuating more than when I use one sensor", see if it helps if you read the same pin twice and ignoring the first result.

4

Triggering three sensors at the same time may give interference, with sensors reacting to each other's ping. Trigger them some 100-200 ms apart, allowing for echoes to die out.

5

I am reading analog voltages of three max sonar sensor devices from three analog pins that is A0 ,A4 and A7 and below is the code for this
anVolt1 = analogRead(A0);
anVolt2 = analogRead(A4);
anVolt3 = analogRead(A7);

Basically my questions are
1.analogRead(A0) is this correct or not.if i am want read from analog pin 0.?
2.For static obstacle position,the values are keep on fluctuating.E.g I placed static obstacle at 3m distance but the values from the arduino board is varying between 1.5m to 3.5m and some times more than 3m that is 770cm like that.

6

I think you need to pay attention to reply #3. You can't run the three sensors at the same time or they'll interfere.

Switch on one sensor, take the reading, switch it off, wait for echoes to die away.

Then switch on the second sensor, and so on.

7

Did you try the suggested changes?

Just triggering / reading one at a time?
Double read?

And why did you not use code tags as AWOL suggested. Time to read How to use this forum - please read.; specifically point 7 about posting code.