I'm producing an Arduino project that has two 5V inductive proximity sensors placed outside the project box.

The project is powered by a Meanwell 12V power supply then to a Murata 5V DC-DC converter which supplies the Arduino and other 5V components, including the two proximity sensors.

The Arduino inputs have a series 1k resistor, TVS diode to ground, and a 10k pullup.


As the project is water-based there is a small risk that the 5V supply for the external proximity sensors could be shorted to the ground and cause the Arduino to"brown out" or reset.

I have considered adding a separate 7805SR regulator, a couple of 0.1uf caps, and a 0.5A PTC fuse as a dedicated supply for the external components powered from the 12V Meanwell PSU. (common ground connections)

Is this a suitable suggestion?

EDIT: sensors are 5v 200ma, the system is powered from a 48V battery.

  • \$\begingroup\$ What is the expected power consumption of the sensors? Something you might consider would be USB current limit chips, sometimes including switch functionality - the benefits being greater precision and that you get a status output when they trip. \$\endgroup\$ Oct 28, 2020 at 21:28
  • \$\begingroup\$ It's very low power consumption 200 - 500ma at 5v. \$\endgroup\$ Oct 28, 2020 at 21:35
  • \$\begingroup\$ 1 to 2.5W not not exactly "very low" it's much more than the arduino uses. \$\endgroup\$ Oct 28, 2020 at 21:37
  • 1
    \$\begingroup\$ and a lot less than a string of ws2811 LED's but yes I see your point. \$\endgroup\$ Oct 28, 2020 at 21:41

1 Answer 1


7805SR (like LM7805) has internal short-circuit protection

so the polyfuse is probably not needed.

Data sheet says

7805SR requires no heat sinks, no temperature derating, no forced-air cooling, and no external capacitors.

so the regulator is all that's needed.


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