Here is a simple Arduino sketch using a pressure sensor to send a signal.  This sketch doesn’t demo what would be input from RAPID, but you can think of it as the sensor data (on analog pin 0 in this example).  Read a pin, monitor the value and if it changes, do something.

This schematic should work for most analog sensors.  The breadboard layout and code were adapted from HERE.  The same website has a link to an open source mini robotic arm…

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//Arduino to I/O for RAPID, ABB control
int pressPin = 0;                      //pressure sensor to Arduino A0
int initReading;                         //variable for the initial reading,
// of the pressure sensor.
int reading;                              //variable for storing current pressure
//reading
boolean startUp;                      //sets up a calibration ‘switch’

int di1Pin = 9;                          //sends signal to robot controller

void setup()
{
//Serial.begin(9600);                  //Setup a serial connection for debug.

initReading = 0;                         //Initialize initReading.
reading = analogRead(pressPin); //Reading equals the value,
//returned by the sensor.
startUp = true;                           //Initialize the calibration switch to ‘on’
pinMode(di1Pin, OUTPUT);         //Pin 9 is set to SEND a signal.

}

void loop()
{
calibrate();                                  //calls the function defined below

reading = analogRead(pressPin);  //Reading equals the value,
//from the sensor
if(reading < initReading*.9)          //If reading is less than 90%,
{                                               //of the initial sensor value,
digitalWrite(di1Pin, HIGH);          //send a signal to the controller.
}
else                                          //Otherwise,
{
digitalWrite(di1Pin,LOW);           //send no signal.
}
}

void calibrate()                          //The first thing to do in the loop,
{
if(startUp == true)                      //if the calibration switch is on (which it is),
{
initReading = reading;                //set initReading equal to the sensor
//value.
startUp = false;                         //And shut of the calibration switch.
}
}