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I am designing a custom breakout board for my ESP32 Devkit-C used as a CNC controller. The ESP is powered from a Mean Well 5 V PSU (with a Schottky diode and some capacitance to ground). In this circuit I’ve got a variety of peripherals (relays, opto-isolated inputs, 3.3 V to 5 V shifting with 74AHCT125s, RS485 etc, as well as pull-ups on pins for input that don’t have internal ones.

In my setup, an enclosure contains 4 PSUs - 3.3 V, 5 V, 12 V and 24 V. 5 V powers the ESP, and the other ones power peripherals (finductive proximity switching at 12 V connected with an opto-isolator to the ESP, 24 V used for LED strips driven by the relay outputs and so on).

In other breakout boards I’ve seen, it seems common that a higher voltage input is used, often 9-12 V, which is then regulated down to 5 V for the ESP.

Given that I’ve got all the PSUs mentioned above, is there an advantage to still include some form of regulation circuitry from a higher voltage over using 5 V from the PSU directly (keep in mind there are other, light load consumers on the 5 V PSU)?

Furthermore, in cases where 3.3 V is needed for the peripherals - what advantages / disadvantages would there be to use the 3.3 V from the esp instead of using the output from the PSU's 3.3 V?

Thanks!

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  • \$\begingroup\$ A direct 5V input can work. Voltage regulation from a higher voltage source offers advantages in terms of versatility and stability. \$\endgroup\$
    – liaifat85
    Commented Nov 16, 2023 at 18:00
  • \$\begingroup\$ most applications, and it sounds like yours too, don't need tightly-regulated and squeaky-clean DC. 5v (usb) and 12v (~50% of wall warts) supplies are far more likely than 3.3v ones to be lying around the work area of people who buy/use breakout boards, and it's easy to drop DC in small current amounts, so that's why you see it so much. You're over-thinking it. If you need tight ADC consistency or are overclocking or want to isolate pulsing power demands from the rest of your circuits, then 5v from a meanwell dropped to 3.3v with an LDO will be a better than using a 3.3v meanwell. \$\endgroup\$
    – dandavis
    Commented Nov 16, 2023 at 21:59

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Given that all 4 PSUs share a common output ground:

Given that I’ve got all the PSUs mentioned above, is there an advantage to still include some form of regulation circuitry from a higher voltage over using 5v form the PSU directly (keep in mind there are other, light load consumers on the 5v psu)?

As long as the current draw from devices doesn't exceed the PSU maximum output current this is fine.

Further, in cases where 3.3v is needed for the peripherals - are there advantages / disadvantages to using the 3.3v pin on the esp vs. using the output of the 3.3v psu?

The 3.3V PSU is likely to be able to deliver more current than the on-board 3.3V pin of the ESP32.

Since you already have several regulated voltage sources within your enclosure I don't see a reason not to use them.

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