Arduino Project - LDR and ServoMotor Sync and Rotate - arduino

Question

Im doing a home project just for fun and Im pretty new to the Arduino, but I do know the basics.
Im creating a automatic venetian blind where it will open when dark and close when bright.
So the slats of the venetian blinds will rotate to a open position when the light sensor detects darkness and rotate to a closed position when the light sensor detects light.
Im using:
arduino uno r3/
continuous servo motor /
led/
LDR (light sensor)/
10k resistor/
This code works for a standard servo motor. I wanted it to work with a continuous servo motor because you can "control it better" and its the one I have.
I guess I will need a if statement something like this:
if light sensor detects dark then rotate the servomotor a to a certain degree and then stop
and if light sensor detects light then rotate the servomotor to a certain degree and then stop.
#include <Servo.h>
Servo servo1;
int sensorPin = A0; // select the input pin for the ldr
int ledPin = 13;
unsigned int sensorValue = 0;
int servoPin = 9;
int pos = 0;
void setup()
{
//Start Serial port
Serial.begin(9600); // start serial for output - for testing
servo1.attach(9);
pinMode(ledPin, OUTPUT);
}
void loop()
{
// For DEBUGGING - Print out our data, uncomment the lines below
Serial.print("Cell = "); // print the value (0 to 1024)
Serial.println(analogRead(sensorPin)); // print carriage return
pos = analogRead(sensorPin);
pos = constrain (pos, 0, 1023);
int servoPos = map(pos, 0, 1023, 255, 0);
int servoDegree = map(servoPos, 255, 0, 0, 179);
servo1.write(servoDegree);
Serial.print("Servo Degree = ");
Serial.println(servoDegree);
int val = analogRead(sensorPin);
val = constrain (val, 0, 1023);
int ledLevel = map(val, 0, 1023, 255, 0);
analogWrite (ledPin, ledLevel);
delay(50);
}

Answer 1

With continuous servo motors, you give up position information. (See this Polou page for details.) This means you won't know when the blinds have reached their open/closed positions unless you also add limit switches. If you go with the switches, then a continuous servo would work. A better solution might be a small gearhead stepper motor like this one from AdaFruit. They have torque but they are much slower than continuous servos.
Key thing is that you don't want to be energizing the motor continuously (which is how standard servos maintain position). That is wasteful and will burn out the motor in something like a blinds application, day in, day out. You want it to do the task and then in loop() wait until the state (light level in your app) has changed. So you would need to keep track of the last light level, then in loop() check if the current light level is different (and greater than some threshold you will have to determine through testing), then change the state of the blinds and store that last level.