Machine Control POE

Programming Support
1

I am newer to Robot C. I am teaching the PLtW: POE course. We have a Machine Control Project and the students have decided to try and create a security system.

Goals: Use a bump to arm the alarm, wait 10 s for person to leave, notice an intruder, after 3 seconds sound the alarm unless the button is pressed.

Here is what I have programmed to try and make it work, but I am running into issues:

task main()
{
     bool enter = false;      //enter = intruder
     untilBump(dgtl1);       //arm the system
     wait(10);
     while(enter==false)
         {
             if(SensorValue[dgtl10]>20)      //no intruder detected using ultrasonic
                 {
                     enter = false;       //no intruder detected
                 }
             else             //intruder detected
                {
                   clearTimer(T1);
                   while(time1[T1]<=3001)
                     {
                        if(SensorValue[dgtl1]==0 && time1[T1]>3000)  //button not pressed within 3 s 
                              {
                                    enter = true; //intruder detected
                              }
                         else       //button is pressed or more than 3 seconds have passed
                             {
                                    enter = false; /*no intruder detected, I want this line of code to kick back out to the initial while statement to continue looking for intruders*/
                             }
                      }

                }
      while(enter) //while an intruder is detected
          {
             while(1==1) //continuously run this code
                 {
                     turnFlashlightOn(port1, 127); //flash lights as alarm
                     wait(0.5);
                     turnFlashlightOff(port1);
                     wait(0.5);
                 }
           }
}

Help! Any and all advice is welcome. Thanks!

2

What issues are you currently having with it?

1 Like
4

Here is an example of how such logic could be implemented with a state machine:

task main()
{
    int systemState = 0; // 0 = system is not activated

    while(1)
    {
        bool controlButtonPressed = (SensorValue[dgtl1]==1); 
        bool intruderIsDetected   = (SensorValue[dgtl10]<20); // ultrasonic detected an intruder nearby

        if( systemState==0 && // system is not activated yet
            controlButtonPressed==false )
        {
            delay(1); // sleep for 1 msec 
            continue; // jump back to the top of the loop
        }

        if( systemState==0 ) // system not activated and control button must have been pressed
        {
            delay(10000); // sleep for 10 sec
            systemState=1; // move system into armed state
            continue; // jump back to the top of the loop
        }
        
        if( systemState==1 && // system is armed
            intruderIsDetected == false )
        {
            delay(1); // sleep for 1 msec 
            continue; // jump back to the top of the loop
        }


        if( systemState==1 ) // system is armed and intruder must have been detected
        {
            clearTimer(T1); // reset timer
            systemState=2;  // move system into pre-alarm state
            continue; // jump back to the top of the loop
        }

        if( systemState==2 && // system is in pre-alarm state
            time1[T1]<3001 ) // and 3 sec wait time had not elapsed yet
        {
            if( controlButtonPressed==true )
            {
                systemState=1; // move system back into armed state
            }
            else
            {
                delay(1); // sleep for 1 msec 
            }
            continue; // jump back to the top of the loop
        }
        
        if( systemState==2 ) // system must have been in pre-alarm state for over 3 sec and button wasn't pressed
        {
             // activate the alarm and continuously run this code
             // there is no coming back from here except for power down
             while(1)
             {
                 turnFlashlightOn(port1, 127); //flash lights as alarm
                 delay(500);
                 turnFlashlightOff(port1);
                 delay(500);
             }
        }
    }
}

It could be somewhat simplified, but I made it more verbose for better readability.

I wasn’t sure what you want to do when the button is pressed within 3 sec of detecting an intruder and intruder is still being detected, so you can modify this state machine accordingly.

1 Like
5

My main problem is that when the bump is pressed within 3 seconds of an intruder being detected, the alarm still goes off. It doesn’t seem to kick back to the original state.

6

As programs are mostly linear, it looks like once the alarm goes off. It leaves the detection loop and the alarm just runs forever. The easiest way I can think of making the system reset is by using another function. One function for the detection loop and one for the alarm going off. And calling upon one another.