Electronics > Projects, Designs, and Technical Stuff
Power supply for an microcontroller kit
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spudboy488:
Low Vfwd diodes to steer the supplies. What I did on my board was to have a 3 pin header and jumper to select USB or external power sources
Richard Crowley:
Study the schematic diagram for most of the Arduino circuits. Most of them have quite clever and elegant implementation of exactly what you are describing.  Automatically selecting either the 5V from USB input, or the 7~12V input from the "barrel connector" (or the header pins, etc.)
technix:
A simple way is set your VIN regulator slightly above 5V (ex. 5.2V for my usual TPS563201 VIN buck converter) and put a diode in VBUS. This way the external power is always slightly higher than USB and there is no risk of backfeeding.

You can read my published schematics for SushiBits ARM Classic, which included VIN to 5V regulator using TPS563201, VBUS/regulator current steering, and a subsequent 5V to 3.3V regulator using TPS562200.
Zero999:

--- Quote from: Richard Crowley on November 01, 2018, 11:51:11 am ---Study the schematic diagram for most of the Arduino circuits. Most of them have quite clever and elegant implementation of exactly what you are describing.  Automatically selecting either the 5V from USB input, or the 7~12V input from the "barrel connector" (or the header pins, etc.)

--- End quote ---

https://eelabs.wordpress.com/2014/04/14/schematic-and-inputoutput-pins-explain-for-arduino-uno-r3/
http://www.fecegypt.com/uploads/dataSheet/1522237550_arduino%20uno%20r3.pdf
romhunter:

--- Quote from: Richard Crowley on November 01, 2018, 11:51:11 am ---Study the schematic diagram for most of the Arduino circuits. Most of them have quite clever and elegant implementation of exactly what you are describing.  Automatically selecting either the 5V from USB input, or the 7~12V input from the "barrel connector" (or the header pins, etc.)

--- End quote ---

Thanks for the tips. I've choosen this design to be implemented in my design. It's quite clever and fit my needs.
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