Connecting Something Big to an Arduino - Sending more than 5V So I am turning a relay on and off with my Arduino. I am using python to control it but wrote the simple basic code in the Arduino IDE. I am able to send 5 or 0 volts to the pin. My question is, how can I turn something on and off that requires more than 5 volts to turn on?

Thank you.
Use a transistor, amplifier, opto-isolator or if you can drive a 5V relay use that relay to drive a higher voltage/current item item.