I'm designing a shield for the Arduino Uno with some sensors that require +5V, +3V3 and +3V Vdd. I want to power everything with a single DC adapter so I have a voltage regulator that converts the DC input (+12 - +26V DC) to 5V DC with a maximum current of 1A. That output goes into the 5V sensors, 3V3 and 3V regulators.

Since this is already regulated power can I connect the 5V 1A output to the +5V pin on the Arduino, bypassing the voltage regulator on the Arduino? Or is it better to have another +10V voltage regulator parallel to the 5V regulator that goes into the 9-12V Vin on the Arduino (that than goes to the 5V voltage regulator on the Arduino)?

If I do the first option, is it then save to have the USB connector plugged in?

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  • 3
    There is no "better", you can do either and both ways are OK to use. You can also just leave a USB connection plugged in, when all the voltages are close to 5 V there is no risk that large (damaging) currents start to flow. – Bimpelrekkie Oct 5 '17 at 14:45
  • "converts the DC input (+12 - +26V DC) to 5V DC" Are you using a switching regulator for that? That'd be most efficient. A part like Murata Power Solutions, OKI-78SR-5/1.5-W36-C, available at Digikey for example. 7V to 36V in, 5V out, 1.5A capacity. Or roll your own from a switching regulator IC; pay attention to the components and layout recommended by the manufacturer. – CrossRoads Aug 1 '18 at 14:19

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