Just to point out to OP in case he didn't notice, that the mosfet suggested by wvmarle is a logic level IRL which can run direct from the Arduino and doesn't need the intermediary npn bjt as shown in billhowl's circuit which is for an IRF
Just to point out to OP in case he didn't notice, that the mosfet suggested by wvmarle is a logic level IRL which can run direct from the Arduino and doesn't need the intermediary npn bjt as shown in billhowl's circuit which is for an IRF