Miduino outputs can only supply up to 40 mA
current from each output. So if driving
circuits with a higher current, or higher
than 5 Volt, some interface
circuitry is required.
interface circuits use transistors to drive
Direct Current (DC) circuits and Triacs to
drive Alternating Current (AC) circuits.
Also Relays can be used to switch either DC
or AC circuits.
Projects dealing with High Voltage DC or AC electricity
can be dangerous. There are many books and websites about electrical safety procedures and if
you are not sure how to be safe you should read that information.