Arduino input voltage?

Hi, I am working on a device that attaches on to the "x-port" of an rc plane that i have. When you press a button on the controller, it sends a signal through a port that I will connect the arduino to. It runs off 8.4 volts, but can the arduino handle that much through a digital Input? If not, how could I fix it?

Ta_anders: Hi, I am working on a device that attaches on to the "x-port" of an rc plane that i have. When you press a button on the controller, it sends a signal through a port that I will connect the arduino to. It runs off 8.4 volts, but can the arduino handle that much through a digital Input?

The maximum input voltage to a standard arduino board is +5.5vdc, higher will damage the chip.

If not, how could I fix it?

The most common solution is to wire the 8.4 volt signal to two series connected resistors to ground. The junction of the resistors will be 'divided' voltage based on the ratio of the resistance of the two resistors. If say they are both 10,000 ohm resistors, then the voltage between the resistors will be 4.2vdc, which is a safe voltage to apply to a arduino input pin. Note that the ground side of the resistors much wire to both the arduino ground and the ground of the circuit supplying the 8.4vdc signal..

You can also use un Zener diode @5V to 'cut' high voltage >5V.