Alarm project, guidance for a new guy

Hello! Im quite new to arduino and it's capabilities. My project idea is that I want to make an alarm system that uses a buzzer, numpad, ultrasonic range sensor, an aruino of course and maybe a couple of LED:s.

I want the alarm to trigger once you get close enough to the sensor (less than 1m) and I simultaneously want the buzzer to start + the LED:s. And the only way to turn off the alarm is by a 4-digit code you input on the numpad.

My question is if these parts will work together and will I have to use an external power supply, like a batpack?

Parts

Arduino = Arduino UNO (MEGA328) rev 3 Buzzer = Piezo transducer 4.5kHz (or suggest a better one) Numpad = A basic 4x4. 2,54mm connection 8 pole Range senor = HC-SR04 LED:s = Just some basic lights A breadboard and cables (because I don't have access to a solder)

I appreciate any help I can get, as I said Im new to this. Thanks! (English isn't my native language so I apologize if anything was messy)

will I have to use an external power supply, like a batpack?

If you want it to run without USB connection then you need SOME power source. A simple 9V 1A "wall wart" is the typical solution for a couple of $.

The rest sounds workable...

Info and some code examples HERE: http://arduino-info.wikispaces.com/UltraSonicDistance

I'd prefer an old mobile phone charger as it outputs 5V.

The rest of the parts will probably work fine with the Arduino. Probably - as you don't provide specific part numbers or the keypad and buzzer, but in general such parts are commonly used with Arduinos. The HC-SR04 and regular LEDs are fine. Just remember to connect no more than one LED per output without additional driver hardware, and add current limiting resistors.