ok so i made the schematic messer and added the mosfet and a pull-down resistor for the gate

EDIT: removed pic

i really like the SparkFun solder http://www.sparkfun.com/products/10243

Yes.
You're in Australia?

ok so with this mosfet http://littlebirdelectronics.com/products/nchannel-mosfet-60v-30a
12V goes into the SOURCE
signal from arduino into the GATE
and the DRAIN goes to the LEDs anode
is that right?


and yes i am in AUS

would something like this work http://littlebirdelectronics.com/products/nchannel-mosfet-60v-30a

ok so i am making a light for a fish tank and i need a to make a power supply that can deliver 12v and 5v at the same time.

this is what i was thinking

the 12v will end up powering the LEDs and the 5v will power the arduino and the RTC.
will this design work or do i need to rethink it.

now my other question is which transistor type do i use to control the LEDs. the LEDs draws about 1 amp.

i am not sure if i should use a P-channel or a N-channel mosfet and i will be using PWM to control the brightness

i hope i explained that well enough 

and if you don't want to play with high voltages and put it relays just rig up a cheap servo to flick the switch

Are you trying to have the Arduino keep track of the time or do you plan to use a RTC (preferred)?

ok so i did not explain what i meant in my original post.
what i need is a way of keeping time
i will have a look for some info on RTC

EDIT: i am think about this breakout board from sparkfun http://littlebirdelectronics.com/products/deadon-rtc-ds3234-breakout

a simple sensor like this will do http://www.sparkfun.com/products/10988
and there is a tutorial on page 26 of this book http://www.sparkfun.com/tutorial/AIK/ARDX-EG-SPAR-PRINT-85-REV-10.pdf

ok i will give it a go now

there is no code this is just theory until i get my parts

hey i am making a light for my fish tank, i will be using 20-30 of theses LEDs http://littlebirdelectronics.com/products/super-bright-led-white-100pcs
i want to make it slowly dim any time after 8:30pm but only if there is not ambient light and then slowly brighten at 7:00am.

the part i am having trouble with is the clock, i just cant work it out

i hope i have explained it well.

ok so the code below is the one i am using and i am now using a 5v regulator and it has fixed the problem of the servo jumping to 90º

Code:

#include <Servo.h>
Servo fan;

void setup()
{
  Serial.begin(9600);
  Serial.println("Starting");
  fan.attach(9);
  delay(1000);
}

void loop()
{
  for(int val = 0; val <= 170; val++){
    Serial.println(val);
    fan.write(val);
    delay(150);
  }
  for(int val = 170; val >= 0; val--){
    Serial.println(val);
    fan.write(val);
    delay(150);
  }
  
}

and it's only the one servo

And that one servo sucks a lot more current than the Arduino can safely supply. But, hey, it's your Arduino.

ok good point.
looks like i will be down at the electronics store in the morning

but when it gets back to 0º it jumps to 90º.

Odd because when I run this the printed output looks fine. Is your printed output fine?
yer mine is fine

could the heat from the voltage regulator be the problem

Put your finger on it is it hot? If you can stand to hold your finger on for longer than 10 seconds then it is not too hot.

Most likely is interference from the motor and fan causing the arduino to reset or crash.
i don't think so it was sitting on my desk next to the laptop

How are you powering the servos? Not from the Arduino, I hope.
yes i was, i do have a 5v regulator but i don't have any caps or perfboard to get it working.
and it's only the one servo

ok so this is my new code

Code:

#include <Servo.h>
Servo fan;

void setup()
{
  Serial.begin(9600);
  Serial.println("Starting");
  fan.attach(9);
  delay(1000);
}

void loop()
{
  for(int val = 0; val <= 170; val++){
    Serial.println(val);
    fan.write(val);
    delay(50);
  }
 
  for(int val = 170; val >= 0; val--){
    Serial.println(val);
    fan.write(val);
    delay(50);
  }
 
}

now it does its 180º anti-clockwise and then 180º clockwise, but when it gets back to 0º i jumps to 90º. i can not find what part of the code is doing this.

P.S. i have it going and it did the loop 5-10 times and then it just stopped and i needed to restart the arduino..... i have it plugged in through the USB and wall socket. could the heat from the voltage regulator be the problem