phototransistor and led

okay so i finally have time to play with my arduino some more! im try to get it so that when the phototransistor see the inferred light that it will turn on an led. im almost sure i have my phototransistor connected right, and i know the led is connected right. but i think that only leaves my sketch, take a look.

int ledpin = 13; // led is on pin 13
int pt = A1; // phototransistor is on pin analog 1


void setup(){
pinMode(ledpin, OUTPUT);
}

void loop(){
  if (pt == HIGH)
  {
    digitalWrite(ledpin, HIGH);
  }
  else
  {
    digitalWrite(ledpin, LOW);
  }
}

i got it! all on my own!

int ledpin = 13; // led is on pin 13
int pt = A1; // phototransistor is on pin analog 1
int val = 0;

void setup(){
pinMode(ledpin, OUTPUT);
}

void loop(){
  val = analogRead (pt);
  if  (val == LOW)
  {
    digitalWrite(ledpin, LOW);
  }
  else
  {
    digitalWrite(ledpin, HIGH);
  }
}

i didnt know my bedroom light can be seen by the pt.

new problem. im trying to get a pot to control how long the led will stay on, after the pt is off.

int ledpin = 13; // led is on pin 13
int pt = A1; // phototransistor is on pin analog 1
int val = 0; // place to store value from the phototransistor
int pot = A2; // pot is on pin analog 2
int val2; // place to store value from pot

void setup(){
pinMode(ledpin, OUTPUT); // declares the ledpin as an output
}

void loop(){
  val = analogRead(pt); //reads the value from the phototransistor
  val2 = analogRead(pot); // reads the value from the pot
  
  if  (val == LOW) // checks to see if val is off
  {
    digitalWrite(ledpin, LOW); // turns led off
  }
  else
  {
    digitalWrite(ledpin, HIGH); // turns led on
     delay(pot); // delays how long the led is off
  }
}

jareeb:
new problem. im trying to get a pot to control how long the led will stay on, after the pt is off.

As in a time delay from when the phototransistor goes off until the led is actually turned off?

In that case, take a look at the Blink Without Delay example. Set the timestamp whenever the phototransistor is on, and if it's been so long since that timestamp, turn it off.

Using:-

if  (val == LOW) // checks to see if val is off

Is wrong. The analogue read returns a value between 0 to 1023 not a logic level.
You need to compare the value to some threshold value, for example:-

if  (val < 100) // checks to see if val is low

This will make it much more sensitive.