I have a background in electronics and I should communicate more on the things I've been debating on for the good of the community.
By far the most useful electronics that you can make in a survival situation is radios (for nonlocal communications and triggers), timers (for irrigation), and power triggers (to give functionality for the other two things).
The question is, in a societal collapse event, what electronics are even useful?
Radios are the hallmark of analog circuits. Even a short distance is very useful. You could set up irrigation timers on each greenhouse or you can have a radio transmitter to a timer and that would send out signals to the receivers in the greenhouse. Communication is useful for security. Just need a bunch of dudes with electric bikes, guns, maps, and radio communications. Anybody needs help a biker gang pulls up. Irrigation timers are useful to reduce the workload, that's what im working on right now.
My mom bought me a raised garden bed and we're filling it with dirt now, I work a lot so I don't have a lot of time but I could set up an irrigation timer circuit and refill it once a week. So far I'm making making it 5v with an arduino nano, 24 hour timer that pumps for 30 seconds to a minute. I'm noticing all the parts are basically crap and I want it to run on a small solar panel and charge the small battery daily.
I notice 12v devices are much better but it's way more industrial and bulky. Look up 12v rechargeable battery, boom, just a bunch of power stations. Nothing like a lithium ion battery, and leaving that out in the sun is not a good idea. So im stuck trying the 5v version anyways.
Anyways, it's progress, farming is fun. I'll say I'm using an arduino nano but in the future I want to try and use much more simpler circuits (resistors, inductor, capacitors, transistors, and diodes). However it just needs to be a sunset detector and activate an hour after, so a photoresistor with op amps for triggers would be a good idea, and then it would be too dark on days it rains anyways to activate. Anyways let me know if you guys have this figure out already. Everything commercially available is just crap, and now I feel bad for farmers.
In a survival situation you won't be able to utilize pcbs however there probably is a way to pour aluminum on a ceramic board and route pcbs that way. With one of those genmitsu cnc rigs. Also 3D printing parts for a pump are useful and they're crap anyways, maybe you'll make a better one.
Anyways those three circuits are very worthwhile to establish communication, and reduce workload drastically.
Tip I've found: i kept having to use Google maps to get home in an area with no cell data, so there's a way to download offline maps and I wonder if the internet goes down you can just your location and it can use accelerometer data to approximate movement. Otherwise, still useful as a map with reference points.
Pick a location, scroll right on the blue buttons before hitting directions or start and select more, download offline maps. Scroll out and try to select the areas you visit most, or your escape routes if you can, I'm unsure if most phones can hold that much data. If anything it'll save you on cell data as well, so there's a little financial independence there.