Here are some useful and interesting blog articles from Digi-Key.
First, a good review and summary of power isolation circuits, I’ve got to keep this in mind:
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Inductive isolation via transformer coils, this is useful for transferring power but keeping the current loops separate.
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Opto-isolators. This is a fairly common traditional electrical isolation mechanism for data cables to prevent ground loops.
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Capacitive isolation. This is a somewhat newer method geared up for electrically isolating data connections, but it can be smaller and more tightly integrated than opto-isolation. Still, it can provide resistance for very high voltages.
Do keep in mind: The simplest way to transfer a digital signal across an electrically isolated gap is to use a modulated frequency for a one, and no current for a zero.
20200316/https://www.digikey.com/en/blog/engineering-and-isolation-its-not-what-you-think
This is a great article that shows one possible design for using solar cells to power a Raspberry Pi 3 with a rechargable battery. One note they make in the article, including the Wi-Fi on-board saves power compared to an off-board USB device. Okay, okay… so maybe I really would want to use Raspberry Pi Zero W for Wi-Fi devices, it’s just that I have to cope with finding a way to setup good Wi-Fi antennas on Raspberry Pi Zero W.
20200316/https://www.digikey.com/en/articles/techzone/2016/jul/how-to-use-solar-cells-to-power-a-raspberry-pi-3-single-board-computer
This is an interesting article that expresses a somewhat personal viewpoint: When will Power Engineering finally get some respect?
20200316/https://www.digikey.com/en/blog/when-will-power-engineering-finally-get-some-respect