Arduino Respond & GSM 900A MINI module

Hi all. I'm a newbie in arduino programming and I really need helps on it for the sake of my final year project.

  1. Why my arduino respond the opposite from it should be for the whole system?

(some said, the logic level turn the opposite) everything went well during the previous testings. we didn't not even touch the wiring nor the pin connection but unfortunately, when I did the final testing, the arduino respond opposite from it should be. (the serial monitor showed my lamp status was ON, but it's OFF during the testing. it also happened to all my project outputs, when its supposed to ON, but it's OFF and vice versa)

so what can I do to solve this problem?

  1. how to notify multiple users via sms using GSM 900A MINI module?

I've tried several methods of programming but nothing works out. so here's the process;

(a) the ultrasonic sensor will trigger the indicator lamp to turn ON
(b) when the indicator lamp turn ON, it will trigger the GSM 900A MINI module to send sms to users about its status and the user will reply OKAY in order to turn OFF the indicator lamp to its initial condition

can anyone help me out with the programming?

Please help me!

You ask "so what can I do to solve this problem?. The answer it to begin debugging your program using Serial.print() to display the variables associated with the problem you are seeing. Only then can you figure out the logic error.

Paul

About the first problem, you have to check if you have enough input power, or check again carefully your code.

GrOnThOs:
About the first problem, you have to check if you have enough input power, or check again carefully your code.

thanks GrOnThOs for your reply.

both arduino and all my project outputs got enough power. I have checked it multiple times using multimeter.
about my code, it was the same code I'm using during the previous testings. and during the previous testings, my project successfully ran the way it should be.

is there anything else that i have missed?

Paul_KD7HB:
You ask "so what can I do to solve this problem?. The answer it to begin debugging your program using Serial.print() to display the variables associated with the problem you are seeing. Only then can you figure out the logic error.

Paul

Thanks Paul for your reply.

I am using Serial Monitor to display all outputs based on the code and what that output status when they interact with all the sensors.

Is that what you mean by using Serial.print() to display the variables?

Newbie97:
Thanks Paul for your reply.

I am using Serial Monitor to display all outputs based on the code and what that output status when they interact with all the sensors.

Is that what you mean by using Serial.print() to display the variables?

No, I am referring to displaying the values in variables used in your logic, ie. compares, for loops, while loops, anything where you make a decision.

Paul