Hi guys. As I’m learning with my Arduino, I’m putting together sketch CIRC-02. The programming side of this is easy, and all my LEDs are working as they should; however, I’m confused why the breadboard is getting power when I only hook in the 5V wire without the ground? The breadboard layout sheet calls for a wire to plug into the 5V and GND but it’s working without the GND wire. I’m running the sketch using only the 5V wire plugged in. Can someone please give me the basics lesson I’m missing here?
I’ve got the board plugged in via USB. Thanks ahead of time for your help.
then I don’t understand why the 5 volt rail is connected on the template anyway. It’s not used. Only the ground line and output pins should be connected. The 5v rail on the breadboard is unconnected to anything. The output pins supply the current to the LEDs and resistors, which would flow through the common GND rail back to the Arduino board.
Only if one LED would be plugged in in reverse would it be possible for current to flow without the ground rail connected. From a certain output pin, through it’s LED and resistor, through the common ground rail to the other resistor with the reverse plugged LED, into another output pin. Output pins can sink and source current, so there could be your hidden ground pin if it was switched to logic low. In this situation 2 LEDs would light at the same time, even though the LED (the reversed) was intended to be turned off.
How are you powering this setup, ie via USB or an external power supply? Even if it’s using an external power supply, your “ground” connection may be accidentally through the house “ground” circuit. USB “ground” is connected to the house “ground” on a desktop (and some laptop) PCs, and the power supply might have the negative terminal grounded?