sorry dave, i really having a hard time understanding that schematic TxT
is FET the name of the transistor and FET is the on the middle of pic?
That's seems true Wawa, but maybe my teacher gave me relay for it's simplicity
Edit:
i just found this site
can i use that low side driver schematic?
And like always i only understand a quarter of that schematic 
blockhunt:
sorry dave, i really having a hard time understanding that schematic TxT
is FET the name of the transistor and FET is the on the middle of pic?That's seems true Wawa, but maybe my teacher gave me relay for it's simplicity
a FET and a transistor connect in very similar ways.
this schematic does show a FET.
the real question is what can you get your hands on ?
if you can get a relay, fine, a transistor ? fine too, an FET ? all good.
without you having one, this is just theoretical.
post 11 shows you can connect your existing relay to a receptcle. then plug in a wall wart, then that will deliver the DC power you need.
Hi,
What is your electronics, programming, arduino, hardware experience?
For what class is this project being done and how long have you been doing this particular class?
Tom... 
i am an IT engineer student, so my hardware and electronics experience is not that big.
I just touch arduino this year, but i am already familiar with it's programming language for years.
It's not for my class, it's for my thesis with embedded system as my topic
Yeah dave, i quite understand that i can use my relay if i plug it into wall socket.
But i prefer it to be battery or other portable because considering where i will put my system (above a water tank), a battery will be better
blockhunt:
i am an IT engineer student, so my hardware and electronics experience is not that big.
I just touch arduino this year, but i am already familiar with it's programming language for years.It's not for my class, it's for my thesis with embedded system as my topic
Yeah dave, i quite understand that i can use my relay if i plug it into wall socket.
But i prefer it to be battery or other portable because considering where i will put my system (above a water tank), a battery will be better
then an FET will be the lowest power option.
I will take note of that
Gotta learn more about FET then
Thanks guys for all your help 
It really help me a lot