Serial Command to Arduino activating Ping Sensors

Projects Programming
2

You need a state vaiable than can remember what state you are in currently based on events in the past.

#define SENSOROFF 0
#define SENSORON 1

int sensorState = SENSOROFF; 

void setup() {
 ...  // keep as is
}

void loop() 
{
    ...
    switch(data)
    {
        case 's' : sensorState = SENSORON;   break;
        case 'z' : sensorState = SENSOROFF;   break;
    }
    if (senssorState == SENSORON)
    {
        /Do something with your sensor here. when you send an 's' via serial, this part will continusly execute every time in the loop until you send a 'z'.
    }
}