Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: VegaObscura on October 17, 2010, 09:17:01 PM
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I've completed my $50 robot, and everything on it works except the LED. As I understand it, a 5v signal is supposed to go from pin 7 (vcc), through the LED and 320ohm resistor, and finally into pin 6. This way when pin 6 is on, no current flows because both ends are +5v and there is no ground. What I don't understand is how turning pin 6 to low is supposed to complete the circuit. I'm very new to this, but to my understanding setting a pin to low sets that pin to 0v, but doesn't short it to ground. Can someone clear this up for me?
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The "voltage" that is used in electronics is always a difference in potential. GND is just a common reference, such that Vcc-GND = say, 5v. Since we always measure a difference, then GND must be defined as the 0v point, since GND-GND = 0v. Thus, any connection to 0v is a connection to GND.
When the controller mentions HIGH and LOW, it really means voltage of Vcc and voltage of GND, respectively. Since all grounds should be common within a circuit, and so all voltages reference to GND, we just say 5v and 0v to make things simple.