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