francois.e
Posts: 12
Joined: Sun Jan 10, 2016 11:16 pm

reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Sat Apr 17, 2021 11:42 am

I will use my raspberry pi units, the 3B or the 4 on a sailboat. The electric supply will come from a 12 V battery. This battery will be charged alternatively by 100 W solar 100 thru a mppt controller, a battery charger or the stator of the outboard marine motor:
https://www.bornagainboating.com/outboa ... -chargers/
I have found an article which provides what is called an AIS (Automatic identification system for boats) which include a system of reverse protection diodes:
https://www.forward.com.au/pfod/CheapWi ... index.html
Apart from diodes, the main component is a power supply chip:
https://www.adafruit.com/product/4683
I would like to use the power supply chip and reverse protection diode part of this setup to protect my raspberry pi 3B or 4. Is this a good idea? How should I implement that for the pi? Alternative power supply and overload protection thru a device which is energy frugal would be the right solution.

Suggestions and comments are really appreciated.
Thanks.

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rpdom
Posts: 18525
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Sat Apr 17, 2021 12:03 pm

That little power convertor board won't work with a Pi. It converts the 12V from the battery to 3.3V for the circuit they show, at a maximum of 1.2Amps.

A Pi 4B should be supplied with 5V at up to 3 Amps. A board that can supply more than 3A will be fine - the Pi will only take what it needs. It is imperative that the voltage be between 5 and 5.2V though. Lower will make the Pi unstable and much higher is likely to cause damage.

5V 3A regulator boards are easy to find and just as cheap as that one. You'll want one with over voltage protection.

For reverse power protection I would just put a Full Bridge Rectifier [/reverb] between the battery and the power circuit. The rectifier must be rated for at least 2 Amps. 5A would be good. With that in place it won't matter which way round it is connected to the battery, it will still work.
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francois.e
Posts: 12
Joined: Sun Jan 10, 2016 11:16 pm

Re: reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Mon Apr 19, 2021 11:22 pm

It gives me food for thoughts. I will come back with the final project or board.
Thanks for your fast reply.

francois.e
Posts: 12
Joined: Sun Jan 10, 2016 11:16 pm

Re: reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Tue Apr 27, 2021 9:52 pm

I have looked for Full Bridge Rectifier rated 5V 2 amp on the net. My research does not come to the right device:
https://www.google.com/search?client=fi ... 2328984886

Any suggestion would be appreciated.
Thanks.

drgeoff
Posts: 11829
Joined: Wed Jan 25, 2012 6:39 pm

Re: reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Tue Apr 27, 2021 10:24 pm

francois.e wrote:
Tue Apr 27, 2021 9:52 pm
I have looked for Full Bridge Rectifier rated 5V 2 amp on the net. My research does not come to the right device:
https://www.google.com/search?client=fi ... 2328984886

Any suggestion would be appreciated.
Thanks.
Those 5 Volt and 2 Amp ratings are the minimum acceptable. Anything higher is acceptable. Yes you are very unlikely to find a bridge rectifier rated as low as 5 Volts.
Quis custodiet ipsos custodes?

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rpdom
Posts: 18525
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: reverse protection diode for raspberry pi 3B and 4, and booting with a usb hub

Wed Apr 28, 2021 8:34 am

As drgeoff said, those are the absolute minimum ratings. Anything higher will do. As the bridge would be connected to the battery, it should be able to handle 12V, not 5V. So 50V or higher would be fine.

You could make one up using 4 x 1N5401 diodes. They are rated 3A 100V, which will handle the 12V load easily.
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