# Can the GND pin handle 5V?

In many tutorials and guides they use the 5V pin, the GND pin and a GPIO pin to control a servo with a JR-plug. In these guides, they didn't use any other components (I.e. resistors) in between. Now I am wondering if this is safe to use for my pi, because I've read on many websites that the GPIO pins can handle a maximum of 3.3V.

Does this maximum of 3.3V apply to the GND pins? Is the GPIO pin in danger to be fried because if the voltage? (-> What can I do to make that circuit safe?)

P.S.: I've tried to measure the voltage that goes through the cables when the servo is attached in its original position, an RC-car, the results were: about 5V in + and -, about 300mV in the signal cable. These results may be completely wrong as I am new to this topic.

Technical details (may be translated inappropriate, please look at the measuring units): • operating voltage: 4,8-6 V • Rotation Speed: 0,2 sec/60° at 6 V • Rotation force at 6 V: 60 Ncm
• JR-plug

• Voltage doesn't go "through the cables". "Does this maximum of 3.3V apply to the GND pins" makes no sense. Rather than asking vague questions about electric current, ask about WHAT YOU ARE ACTUALLY TRYING, describing actual components and connections, plus software you may be using. Commented Dec 17, 2016 at 22:16
• @Milliways This "voltage goes" fault is more of a language fault as I am not a native English-speaker/-writer. With "Does this maximum of 3.3V apply to the GND pins?" I wanted to ask whether a voltage >3.3V on a ground pin would break the Pi. Also, I am describing that I want to control a servo and that I am worried about connection faults that could break the board; in this early stage I haven't used any software. Commented Dec 17, 2016 at 22:34
• Voltage on a pin makes no sense. Voltage is a potential difference BETWEEN 2 points - normally between (what is commonly referred to as) Ground and some other point. You CANNOT put a voltage ">3.3V" or any other BETWEEN Ground & Ground. Most servos use `PWM` as control, and need to be connected to a specific pin on the Pi. Commented Dec 17, 2016 at 23:06
• @Milliways Oh, I must have got that wrong... Thank you! Commented Dec 22, 2016 at 13:15