There is a comprehensive atricle on the Arduino Uno Power Supply on technobyte

The Uno board can operate on an external supply from 6 to 20 volts via the power jack. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

If the power jack input voltage is 7V or greater, the Uno will use power from the jack, even if the USB port is connected. Only the data lines are used, not the USB +5V power.

The USB port of the Arduino Uno can be connected to a desktop/laptop. If the connection is enumerated, i.e. the computer recognizes the device, the current supplied to the board is 500mA at 5V. If the connection is not enumerated, 100mA is supplied at 5V.

It is possible to power up the Arduino using the 5V and GND pins, provided that the input given is steady and regulated 5V. The 5V pin bypasses the voltage regulator and all the safety measures present on the Arduino Uno, so if the input exceeds 5V (5.5 is the maximum upper limit), the board can be damaged.

You can power a LED strip and the Uno from a regulated +5V supply by connecting the +5V to the Uno +5V pin. There is a risk that if power is connected to the DC input jack and the external +5V is turned off or unplugged, excess current can be drawn through the Uno regulator. To prevent this, use a Schottky diode in series with the +5V input wire as a steering wire. You can use a BAT85 200mA.

The interface shields used on Arduinos are made from discrete component. This DroneBot Workshop MOSFETS and Transistors with Arduino  electronics tutorial gives detailed descriptions of MOSFETS and transistors data sheets, how to choose a suitable device for a suitable interface, then write a sketch to test the example.
17 minutes TIP120 transistor
Be careful inserting the legs of the TIP120 transistor into your breadboard as they are large.

24 minutes DC Motor
Be careful inserting the legs of the TIP120 transistor into your breadboard as they are large. Leads have been soldered onto the potentiometer, with care some potentiometer legs can fit into a breadboard.

30 minutes MOSFETS to control RGB LED Strip with potentiometers to control brightness.
Be careful inserting the legs of the MOSFETS and potentiometers into your breadboard as they are large.


Page updated 10 September 2020