how to use ultrasonic sensor hc sr04 and gps neogps 6m and gsm sim900 on arduino uno - arduino-uno

Question

I’m trying to send an sms with the location when the ultrasonic sensor measures a certain distance but when I add the gpsSerial(9600) line in the void setup, the ultrasonic sensor readings become inconsistent such as it reads 24 cm then skips to 18 cm then back to 24 cm. i would really appreciate it if anyone familiar with arduino or has faced this problem before would help me out. here is my code:
#include <TinyGPS.h>
#include <SoftwareSerial.h>
#include "NewPing.h"
#define TRIGGER_PIN 7
#define ECHO_PIN 8
#define MAX_DISTANCE 100
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
float duration, distance;
SoftwareSerial gsmSerial(2, 3);
SoftwareSerial gpsSerial(5, 4);
TinyGPS gps; //Creates a new instance of the TinyGPS object
bool newData = false;
void setup()
{
Serial.begin(9600);
gsmSerial.begin(9600);
gpsSerial.begin(9600);
}
void loop()
{
// Send ping, get distance in cm
distance = sonar.ping_cm();
if (distance < 4 )
{
//sendSMS();
Serial.println("Bin is full!!, SMS SENT!!");
Serial.println(distance);
delay(1200);
}
else
{
Serial.println(distance);
delay(2000);
}
delay(2000);
}
void sendSMS(){
// For one second we parse GPS data and report some key values
for (unsigned long start = millis(); millis() - start < 1000;)
{
while (gpsSerial.available())
{
char c = gpsSerial.read();
//Serial.print(c);
if (gps.encode(c))
newData = true;
}
}
if (newData) //If newData is true
{
float flat, flon;
unsigned long age;
gps.f_get_position(&flat, &flon, &age);
gsmSerial.print("AT+CMGF=1\r");
delay(400);
gsmSerial.println("AT + CMGS = \"+26xxxxxxxx\"");// recipient's mobile
number
delay(300);
gsmSerial.print("BIN IS FULL!, PLEASE COLLECT # https://www.google.com
/maps/?q=");
gsmSerial.print(flat == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flat, 6);
gsmSerial.print(",");
gsmSerial.print(flon == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flon, 6);
delay(200);
gsmSerial.println((char)26); // End AT command with a ^Z, ASCII code
26
delay(2000);
gsmSerial.println();
}
}

Answer 1

I've tried to reproduce your problem on Arduino Uno with HC SR04, but with no success – my measurements were stable (more than 100 same measurements in a row). I have even set the sensor to 24 cm distance from the measured obstacle. I used a code derived from what you have provided:
#include <SoftwareSerial.h>
#include "NewPing.h"
#define TRIGGER_PIN 7
#define ECHO_PIN 8
#define MAX_DISTANCE 100
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
float duration, distance;
SoftwareSerial gsmSerial(2, 3);
SoftwareSerial gpsSerial(5, 4);
void setup() {
Serial.begin(9600);
gsmSerial.begin(9600);
gpsSerial.begin(9600);
}
void loop() {
// Send ping, get distance in cm
distance = sonar.ping_cm();
if (distance < 4 ) {
Serial.println("Bin is full!!, SMS SENT!!");
Serial.println(distance);
}
else {
Serial.println(distance);
}
delay(2000);
}
My conclusion is your code is fine and the problem is HW related. Check the wiring and if possible, try to use another HC-SR04 sensor.
BTW1: During testing, I was sending data to gpsSerial (rx) just to be sure, it is not caused by the GPS module sending some periodic data.
BTW2: How do you power the GPS and GSM module? Are you using Arduino to power these? If yes, this also can be the source of your problems since these modules could drain large peak currents and Arduino as source is not powerful enough ...