I hope you can help me - I¨m sure it's not too complicated, I just know yet how to ask my Arduino to read it.
So, I'm playing peek-a-boo with my robot (arduino, light sensor and a motor)
and I need to tell my arduino to read that:
If the value of the LDR (which is usually around 600) goes below 100 (for more than 2 sec) and then above 400, it should trigger the motor.
Thanks a bunch,
Trommp, and Moon (the robot)
Paste this into an empty Arduino IDE and try it
/* simple untested LDR trigger for Moon (the Robot). Smoothing may be required.
See the “analog > smoothing” example on the official arduino website */
boolean firstTrigger=false; //tells the duino if the LDR level is below 100
const int sensor=0; //or whatever your LDR sensor is.
const int MotorPin1 = 4; //or whatever
const int MotorPin2 = 5; //or whatever
void setup(){
//initialise your motor pins
pinMode(MotorPin1,OUTPUT);
pinMode(MotorPin2,OUTPUT);
}
void loop(){
//trigger timer loop by initial activation.
if (analogRead(sensor) < 100){
//2 second timer loop. LDR of greater than 100 will break the loop, thus going back to start
for (int i=0; i < 200; i++){
if (analogRead(sensor) > 100) break;
if (i == 200) firstTrigger=true;
delay(10);//10 x 200 = 2000 ms = 2 seconds
}
}
//we’ve made it at least 2 seconds on low
if (firstTrigger){
if (analogRead(sensor) > 400) Motor();
}
}//end of primary loop
void Motor(){
//assumes an H-bridge of some sort
digitalWrite(MotorPin1,HIGH);
digitalWrite(MotorPin2,LOW);
}
oops
probably want to change the “200” in the for loop to “201”:
for (int i=0; i < 201; i++){
you might want to do a while
you might want to do a while loop instead and keep checking after the 2 seconds is up otherwise the user would have to move their hand at exactly 2 seconds which would be unlikely
it’s a flag
Not so. Once the 2 continuous seconds is over, then the trigger boolean is true. The timing doesn’t matter after that point.
You are so helpful! 
Thanks a bunch!
It’s not working yet - but hopefully soon.
Why do we have motorPin1 and motorPin2 ?
for the motor
The code just assumes that you’re using an H-Bridge for your motor, in which case you would need 2 pins. If you only need one direction for your motor, one pin is all you need. Google “H-bridge” if you have any questions about what that is.
It works!!!
Brilliant!
Now we can play peek a boo all day 
We had to change it a little - but used the base.
Ahhh true… I guess because
Ahhh true… I guess because it’s a different way than I’d do it for some I couldn’t get into my head how the code flowed properly 
