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I bought a resistor in order to make a simple circuit via the GPIO on the Pi, and I accidentally told him I will have 12 volts running in the circuit, so he gave me a specific resistor to handle the 12 volts (I forgot which ratings).

Question is, how many volts does the Raspberry Pi actually output through the GPIO? Is it safe to still use the resistor I have that was actually for 12v circuits?

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The Raspberry Pi uses 3.3v GPIO.

Whilst the resistor will probably not get damaged, it is likely to be too large depending on what it is actually doing. For example if trying to reduce power to an LED nothing will go wrong, but it is unlikely the LED will light.

See the eLinux - Raspberry Pi low-level peripherals page for more information on the GPIO pins.

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Resistor's rated voltage is a distant property of minimal significance, especially in low-voltage applications (<24V).

The resistor's primary property is resistance, which, following Ohm's law, limits current according to voltage applied to it. Still, too high voltage will damage the circuit, even at minimal current, and too high current will damage it even at fairly low voltage. The resistor itself will not help much.

GPIO of RPi can source or sink up to 16 mA at 3.3V. (source)

You should post where/how you want to use the resistor, and what resistance (ohm) it has. Depending on configuration, it may work just fine (as pull-up/pull-down, protection in low-amperage logic), make your circuit simply not work (powering a more current-hungry sink device, or providing current from too weak source) or fail to protect RPi and lead to burning it (sinking overcurrent, voltage divider etc.)

At least, at 16mA 3.3V it's about impossible to burn the circuit you're to connect; there are only uncommon 1.6V electronics rated for lower voltages that could be damaged by it; most of others mismatching simply won't work. Still, it means if you are e.g. reading a 5V signal with your RPi as input, and the resistor was to pull it down to 3.3 through a voltage divider, it will fry your RPi's port before you know it.

  • Much appreciated for the in-depth info, helped me understand much more – BrownEyes Sep 16 '13 at 9:26

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