Controlling external power via relay with Nano 33 IoT

Projects General Guidance
1

Hi,

I'm new to Arduino and I have a Nano 33 IoT I'd like to use to switch on a Raspberry Pi 4 B. As I understand it, since the Nano 33 outputs 3.3V and the Pi takes 5V, controlling power directly is a no-go. Both devices will be powered via wall outlet, so absolute minimization of power consumption is not an issue.

Googling and reading this forum led me to think that a 3.3V relay would suit my purposes but I have questions:

  • Am I going to run into issues controlling a 5V device with a 3.3V relay?
  • How do I pick a reliable relay? Seems like there's a lot on Amazon.
  • (Maybe beyond the scope of an Arduino forum) I intend to software shutdown the Pi when not in use. If it's shutdown via software, it requires a power cycle to reboot. The easiest solution in my mind is when the Arduino is triggered to power on the Pi, if it's already high, switch the relay off and then back on after a second or two. Is there a better way to do this? Maybe using something other than a relay?
2

Usually it works sending a 3.3 volt logic signal to a 5 volt device.
What does "switch on" mean? Logic trigger or total power supply?

3

why not just use a WiFi controlled mains socket?

4

Logic trigger like shorting pins on the Pi itself versus turning on/off the power supply? Either should work, I think. If I've got everything right, the OS running on the Pi should always shut down before power is cut.

Because I didn't know they existed :grinning:. That said, I'm looking into these and it looks like all of them require a phone app or an internet connection or both? I'm looking to write some scripts on my Desktop computer that will power the Pi back up when I need it, and I absolutely do not want any part of this to require a connection to an outside network.

5

Are the controllers near each other? Then having and common GND and a logic signal would be preferred.

6

I can make that work. Awesome, thank you!

7

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