I would add:

• if you wanted direct and low-latency access to cameras (for machine vision)

It sure is possible.

A typical “obscenely bright” LED chip might be Cree XML, but many similar chips exist. You’d need a plano-convex or equivalent Fresnel lens - shorter focal lengths favour compact design. Then you need a driver. Some are fixed while some adjustable with a tiny potentiometer. You’d need an 18650 cell holder (it can be made too, an 18650 will go into a leftover piece of 20 mm electrical cabling pipe with a spring-loaded metal cap engineered of something).

Myself, I bought a nice head lamp, but it broke after one year. The driver board failed. Being of the lazy variety, I replaced the board with a resistor to limit current and now it’s been working 3 years already. Not at peak luminosity, the resistor wasn’t optimal of course. :)

Thanks, that looks like something I might have to try. :) Myself, over the network, I still don’t do filesystem level incremental backups, sticking to either directories or virtual machine snapshots (both of which have their shortcomings).

I’ve been hearing about ZFS and its beneficial features for years now, but mainstream Linux installers don’t seem to support it, and I can’t be bothered to switch filesystems after installing.

Out of curiosity - can anyone tell, what might be blocking them?

Edit: answering my own question: legal issues. Licenses “potentially aren’t compatible”.

Due to potential legal incompatibilities between the CDDL and GPL, despite both being OSI-approved free software licenses which comply with DFSG, ZFS development is not supported by the Linux kernel. ZoL is a project funded by the Lawrence Livermore National Laboratory to develop a native Linux kernel module for its massive storage requirements and super computers.

Source: https://wiki.debian.org/ZFS

From a person who builds robots, three notes:

1. Camera

Raspberry Pi has two CSI (camera serial interface) connectors on board, which is a considerable advantage over having to deal with USB webcams. This matters if your industrial robot must see the work area faster, your competition robot must run circles around opposing robots, or more sadly - if your drone must fly to war. :( On Raspberry Pi, in laboratory conditions (extreme lighting intensity), you can use the camera (with big ifs and buts) at 500+ frames per second, not fast enough to photograph a bullet, but fast enough to see a mouse trap gradually closing. That’s impossible over USB and unheard of to most USB camera makers.

2. Optimized libraries

I know that Raspberry Pi has “WiringPi” (a fast C library for low level comms, helping abstract away difficult problems like hardware timing, DMA and interrupts) and Orange Pi recently got “WiringOP” (I haven’t tried it, don’t know if it works well). I don’t know of anything similar on a PC platform, so I believe that on NUC, you’d have to roll your own (a massive pain) or be limited to kilohertz GPIO frequencies instead of megahertz (because you’d be wading through some fairly deep Linux API calls).

3. Antenna socket

Sadly, neither of them has a WiFi antenna socket. But the built-in WiFi cards are generally crappy too, so if you needed a considerable working area, you’d connect an external card with an external antenna anyway. Notably, some models of Orange Pi have an external antenna, and the Raspberry Pi Compute Module has one too.

That is quite a lot of interesting experiments, thanks for introducing. :)

I’m inclined to add one more:

51: monitor the radio spectrum for drones (and if their signature looks hostile, warn people about them) - there’s a DIY recipe for a monitoring station out there somewhere, and some Ukrainian guys scan their sky using HackRF

SDR is definitely a technology worth learning. I’m already a happy user of RTL-SDR, but if I want to really see what my WiFi is doing, I should get a HackRF eventually too. (Note: WiFi is too fast to intercept without loss, except with another WiFi card, unless a slower bitrate is deliberately chosen.)

Trying to figure out how my heat pump supposedly supports WiFi… in unfathomable and non-standard ways. It’s available as an access point, I can associate and ping it, but no TCP ports listen and no UDP port responds. Nothing cool, undocumented features down to the rocky bottom. When you buy a heat pump and plan to automate its use, check out supported protocols before making a decision. :)

Unfortunately, yes.

I’ve had multipe experiences with seeing a flashlight battery which, according to labels, ought to have the capacity of an electric vehicle cell. And of course they don’t - on EBay or AliExpress, there’s a 100% chance that they’re just deceptively labeled. :)

If one needs high current, measuring the current with a known and low resistance (e.g. car headlight bulb) helps.

If the soil is dry enough to avoid liquefication, lifting should not happen. A ditch around the pool with drainage to lower ground at some distance would likely solve the problem even if the soil is problematic.

If the concrete is reinforced with rebar, it can withstand sideways load by the soil. If not, the issue of soil pressure would need closer consideration.

Disclaimer: I’m not an engineer

Still building a DIY tractor / excavator - racing against time, as autumn is rainy here and you cannot weld water. I need it to improve the road to where I live.

It can already maneuver, turn and raise the boom, lower / pull the bucketed arm (stick), but the excavator bucket is incomplete and the bucket tilting mechanism missing.

The remote control system is also missing (relays on a slow boat from China), so currently I have to control it via cables. Limit switches are missing, currently it’s unsafe to use for a careless operator. Later on, it will be remote controlled and limit switches will ensure it cannot break itself.

My own reason to choose remote control is convenience (better ergonomics as I can write pre-programmed movements and stay out of noise). If it works too well, I might send a recipe to a friend in Ukraine, with the suggestion of asking around - maybe someone needs cheaper mine disposal machines.

Hydraulic excavators are neat, but too expensive for me, and require far too much power. Thus mu excavator uses ATV winches (meant to pull a 900 kg machine out of mud) to drive and work. Some of the winches have been disassembled: driving uses sprockets and “08” roller chain, turning the boom also uses sprockets and chain. Some of the winches are intact however: raising the boom uses a winch in factory condition, and pulling in the bucket in also uses a winch.

A big corner has been cut to gain strength asymmetrically and reduce complexity: I assumed I’m never going to do a pushing movement with the bucketed arm. So, where old-fashioned cable excavators used a super complicated winch system to extend the arm, I use a boring simple gas spring. Near-zero pushing-out power to gain the absolute maximum pulling-in power.

I would recommend motor silicone, since it’s often rated for 300 C. The surface being sealed should be scratched or sanded for better adhesion. After it has fully cured (several days), one should probably do about ten “test boils” to flush out anything that might seep into water.

Looks very nice and practical. :) Congratulations. :)

I have tried polycarbonate, with miserable results. The clear silicone did not not adhere well, and thermal expansion ratios were in mismatch - the panel destroyed itself soon, interior components separated from the polycarbonate, the panel was mounted vertically and deformation started (tracks started curving downward).

Test thoroughly and if you have doubts about mechanical resilience, maybe use the panel horizontally.

Glass is a silicate, and may have the unique advantage of expansion ratios matching silicon wafers.

Or a solar concentrator and a steam / Stirling motor.

Useful trick, worth knowing. :)

A ram pump is to water what a switching mode power supply is to electricity. You can use inertia (inductivity) to raise pressure (voltage).