Question regarding purpose of a diode

Other Hardware General Electronics
1

Hello! I am currently building a quadcopter based on Joop Brokkings model, which uses an Arduino is a flight controller. The build is progressing fine, but there is a certain part of the circuit I do not really understand. I will attach a picture of the schematic, which can also be seen at 6:38 in the following video. (Your Multicopter Flight Controller - 3D (YMFC-3D) Part 1 - Hardware. - YouTube)

There is a diode connected to the battery, which limits the current travel into the direction OUT from the battery. However, in the video, it states that it "prevents the USB-power from feeding the ESC:s and motors", and from the website it states that "the diode D1 protects the USB-port when the Arduino is connected to the computer".

I cannot grasp how exactly the D1-diode accomplishes this task, by the look of the attached circuit. Can someone explain this to me? How is the USB-port even affected by the diode?

schematic.png
schematic.png1038×579 245 KB

schematic.png
schematic.png1038×579 245 KB

2

Hello,

The usb port is a source of power.
The battery is a second source of power.
If the battery voltage is too low, the power (current) of the USB will flow into the battery.
As the battery is low impedance, it will take a lot of current possibly overloading the USB power source.
The diode makes sure that in the case usb voltage is above battery voltage that no current can go back into the battery.

Best Regards,
Johi.

3

There is no direct connection from Vusb to the VIN pin, more internet hogwash.