Servo motor not working as expected in elseif statement

Projects Programming
1

I designed a coding for gas leakage detection and cutoff system. And the coding is provided below

#include <Servo.h>
int gas;
int pos;
Servo myservo;
void setup()
{
  pinMode(7,INPUT);
  pinMode(LED_BUILTIN,OUTPUT);
  myservo.attach(6);
  Serial.begin(9600);
}
void loop()
{
 gas = analogRead(A0);
 Serial.println("Gas Sensor");
 Serial.println(gas);
 delay(1000);
 if(gas > 100)
  {
    for (pos = 160; pos >= 0; pos -= 1) 
    {
    myservo.write(pos); 
    delay(15);
    break;
    }
    digitalWrite(LED_BUILTIN,LOW);
  }
  else if(digitalRead(7)==HIGH)
  {
   for (pos = 0; pos <= 160; pos += 1) 
   {  
    myservo.write(pos); 
    delay(15);
    break;
   }
  }
  else
  {
    digitalWrite(LED_BUILTIN,HIGH);
  }
}

I expected that the servo motor will rotate from 160 to 0 degree when the gas sensor gives the reading of greater than 100 and maintain in the position till I press the switch which is connected in digital pin 7.

But the servo motor rotates from 160 to 0 degree when the gas sensor reading is greater than 100 and it comes back to its original position (160 degrees) when the reading of gas sensor is less than 100.

As I am newbie to arduino, and still learning, I know that I've done some mistake in coding... i will be pleased to know what changes should i do in coding...

i am using an arduino nano with atmega328 (old bootloader)

2

Welcome to the forum

if(gas > 100)
  {
    for (pos = 160; pos >= 0; pos -= 1) 
    {
    myservo.write(pos); 
    delay(15);
    break;
    }

It does not do that because you break; out of the for loop after writing the first position to the servo. Remove the break statement

3

If remove the break statement the servo motor works as usual and not stops

After appying the break statement, the servo motor stops after moving from 160 to 0 degree which is what I want

But the actual problem is, the servo motor comes to original position when the reading of gas sensor is less than 100, but i need the servo motor to remain in its position until I press the switch

4

Do you have a pullup or pulldown resistor on your button input, or is it 'wide open' when the button is not pressed?

5

The image in this post may help:

6

Only way your code can drive it back, is that it sees pin 7 high.

7

It's just a normal switch and I think it doesn't have any resistors...

8

Then you have an open input, and the input level at your digitalRead() will be whatever it chooses to be. You need to either wire the button to ground, and use pinMode(pin,INPUT_PULLUP), and watch for a low pin in your code, OR, you need to provide an external resistor from the input pin to GND. Your choice; your present approach will not work.

9

Ok but as i said earlier... I'm a newbie in this field... Can you make things clearer???

10

A digital input with nothing attached, which is what your button input is when the button is not pressed, is a very high input impedance antenna, and will receive noise from waving your hand over the circuit, the local radio station, and just about any other significant rubbish out there. To receive a proper logic level low or high, it must always have a circuit path to GND or +V. A "pullup resistor" wired from input pin to +5V suffices. So does a "pulldown resistor" wired from input pin to GND. With the '328PB processor in the Nano, you have the option of using a pullup resistor built into the chip itself; very convenient. To do that, you specify
pinMode(pin, INPUT PULLUP);
in setup().

What you have now will randomly, but very frequently, get either a high or a low, and that randomness will confound any attempt to build sane logic around the pressing, or not pressing, of a button.
With a pullup in place, external or internal, you can wire your button from input pin to GND, and
if(digitalRead(pin) ==LOW)
will test for the button being pressed.

Does that help?

11

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