In practice that’s a kind of “no true scotsman” argument though. Libertarians who actually believe in libertarian ideas are really pretty scarce (and I’d say they’re closer to anarchists in thought than most people, though potentially the cool kind of anarchist). Most self-described libertarians either want the government to regulate everyone but them, or they cluelessly take for granted the benefits of the way their world is utterly supported by non-market forces (the house cat analogy).

That makes sense, it forms a simple snubber network. A capacitor in series with a low-value resistor might work even better. Did you try a freewheeling diode directly across the valve leads?

I see green roofs on commercial buildings around here sometimes but I don’t think I’ve seen one on a private home. Would you recommend it? Does it help keep the house at an even temperature?

That’s interesting, so you can flip the relays all you like without trouble as long as the 24DC supply isn’t connected? If that’s true then your problem presumably isn’t the typical inductive kick from the relay coil. It looks like your relay board has stuff on it which is presumably drivers and snubbers so let’s assume all of that is adequate to the job.

So, if it’s inductive kick from the valve solenoid it’s being coupled all the way from there, back through the 24DC supply to the outlet, then forward through the USB supply to your shift register, which is impressive! But not implausible.

Anyway, three places I’d add some stuff:

• The main thing you need is a snubber network across the valve solenoid coil itself, ideally physically close to the valve (you want to minimize the area of the loop formed by the valve coil - wiring - snubber). Something as simple as a freewheel/clamping diode would probably help a lot. This will also improve the lifespan of your relay contacts which are probably arcing a little.
• Small decoupling cap on your breadboard, say 0.1µF on the power supply rails, to keep your logic happy.
• Larger decoupling cap on your 24VDC rails (the bus on the left), just to eat any transients the snubber doesn’t deal with. Maybe 1-10µF or so?

It mostly doesn’t matter.

If it’s a high-current, high-frequency, or low-noise circuit then maybe the inductance or resistance of those traces would matter, but they’re very short so probably not.

If you’re mass-producing it, then sometimes the reflow or wave solder process works better if the traces leave the pads in particular ways. You’d talk to your manufacturer about this.

If this is a hobby project, you’re overthinking it; arrange them in a way that pleases you!

Or he’s just getting really into the persona of an 1870s immigrant, who would have been using traditional characters anyway! Such attention to detail :D

Haha same! And shuffling through drifts of leaves in the fall.

I would love to see some legit science pamphlets in the style of Chick tracts…