Boat Computer / Smart Mirror (Power Question)

Hi there lovelies.

I’m using a Rasp Pi 4 with Openplotter & Moitessier HAT 2 and putting this together as a backup plotter (and Boat Computer) for my sailboat.

I’ve just ordered a 14" screen from Pimoroni which requires a 12V/1A barrel jack (5.5 / 2.5mm, centre-positive). This is cool as most of my boat runs off 12v electrics.


I noticed on a review that some clever person had created a harness by which it powered the Rasp Pi AND the screen from 12v (it seemed to suggest one of them used 5v which…er…confused me).

my intent is to have the Rasp Pi squirrelled away with the 14" screen being used as part of a ‘Magic Mirror’ and -ideally- a second screen used in an ad hoc fashion for conventional OpenPlotter stuff

My electrics skills are ‘basic’ meaning that I can wire a black wire and red wire in of the correct thickness so it doesn’t melt and I understand circuits.

So my question is :

  • Is there a single harness that could manage both the above 14" and Rasp Pi? - something I could buy or emulate?
  • What’s the simplest way of powering the Rasp Pi 4 over 12v? - again anything I could just buy and wire in or emulate?
  • Is there anything else that i’d need to consider in terms of making this ‘duel screen’ 12v system work without blowing up or melting my home?

Thanks in advance for any advice or links you can proffer :)


That person likely used a Buck Converter to get 5V for the Pi
MPM3610 5V Buck Converter Breakout - 21V In 5V Out at 1.2A – Pimoroni
UBEC DC/DC Step-Down (Buck) Converter - 5V @ 3A output ID: 1385 - $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Hah! shows what I know - didn’t even realise the RPi4 was 5v.

So I guess I could build a harness that’s a simple red/black 12v then splits into one route going through the buck converter for 5v and the other route continues as 12v for the screen? as long as I don’t underspec the cables and add a fuse etc :)

That should work…