How about a sealed tube with 2 copper strips down the inside, then measure capacitance?

Kind of like this:
https://www.instructables.com/id/Capacitive-Fluid-Level-Sensor/

Hmmm. Looking up scintillometers, I see they are advertised as "large aperture", so you may need an array of photo[diodes,cells], which adds a lot of complexity, matching, summing etc,but maybe you could get away with a condenser lens.

Wikipedia has some clues. A scintillometer which measures fluctuations in refractive index of air, just add math.

Satellite imagery +math

Lysimeter - measure the weight of a column of soil, im guessing dry soil is lighter.

All of thoose sound like lots of money.

A scintillometer seems doable as diy. For an area like a tree, I'd start with a laser diode ( i dont know which frequency, but as a complete guess id try infrared, possibly red, and stay away from green and blue), the other end would be either a phototransistor or a photocell. A low noise (probably high gain) amplifier and a quality anolog to digital converter (maybe a 24 bit sound card, probably a pi zero attached not an arduine or esp)

This is all very speculative(pun intended) on my part, it could be completely wrong, i am guessing based on the few words in wikipedia.

Wikipedia

I know WAF is not a joking matter, but I immediately heard Greg Kihn sing, " my WAf's in jeopardy, baby".

Mycroft has some of that. www.mycroft.ai

@naty6458 no need to be sorry. I keep hoping there is a better answer than what I found, and each time it is asked I learn something, so there is at least one person that is happy you asked.

My plan is optocouplers, maybe a rechargeable coin cell to help power them. I want to connect to the pins for the rf receiver. I should be able to send the same code the remote uses to turn it on and off. Since I wont be sending codes often the coin cell should be fully charged most of the time, so the low capacity (~23mah) shouldn't cause a problem, unless someone flicks the lights on and off repeatedly.

I'll power the arduino/rs485 module separately.

This is the $64,000 question. I've seen discussions about it, but no solution. You could build a separate power supply that floats on the ac like the built in one, they work by leaking a small amount of current and can cause flickering, especially with LED lights. Two supplies double the chance of flickering.

If your arduino can spend most of its time sleeping, you might be able to charge a battery or supercap to run it.

There is a lot out there on lowering power consumption on arduinos, remove LEDs, lower clock speed, etc. Maybe a bare bones chip, with just the connections you need.

Or

Use optocouplers to connect the arduino to the livolo, and use a normal power supply for the arduino.

If any of my old x10 gear looked that good I would just make new pcbs and relabel the buttons.

https://www.maximintegrated.com/en/app-notes/index.mvp/id/148

Here is maxim's guide on wiring for 1-wire. There are a few things to note, one is the "weight" of each sensor's cable. Read that section closely. Another is hubs. Hubs are basically a 1 wire switch that connects each segement of the network 1 at a time, so you can essentially walk though each ray of your star. The third is the suggestion above to use multiple pins on the arduino and just make several simpler networks.

Is it any 5th temp sensor? In other words could it be a bad temp sensor? Also 1-wire doesnt like 'star' wiring, are all the sensors wired with short connections to the main cable? More like ,, and less |_| and for sure not |/

I may misunderstand how they work, but I've had the idea that (super)caps are better in short term high current situations. Like regenerative brakes for robot lawnmowers, not slow drain low power devices. It sounds to me like the life boat is the lifepo4 batteries. I'm all for experiments, so please dont stop, but unless the environmental conditions are intolerable for the batteries, I'd say you found your answer.

So these radar motion sensors are actually quite impressive, the ones with just analog output only have 1 transistor, the rest of the circuit is formed by the pcb traces. Weird, but it works. They can be hacked (sawtooth wave for power) to give a distance reading instead of doppler. The signal processing is too much for an arduino, but it is doable.

The other ones actually use the same chip as the most common pir devices.

I'm going to go a bit conceptual here, riffing on some ideas that I believe I got from @dbemowsk. A multi-pronged approach may be useful here, maybe bt for the car and bicycle, amount of time since any PIR device triggered, time of day, etc. Then using the "smarts" of a smarthome a reasonable estimate of home/away can be gained.

I dont think an A.I. like the googazon has is required, but something smarter than a single node might be apropriate.

Would somesort of passive rfid tag attached to your keychain work?

Edit - a quick google search for keyfinder came up with a variety of bluetooth/gps tags, some in bulk for under $2 USD. Probably come with an app, but that could likely be subverted into something mysensors compatible.

Is the level shifter closer to the 5v arduino? Or the 3v? Maybe losses in the cable are dropping the voltage below 3v. So maybe level shift after the cable run.

https://github.com/dukelec/cdbus_doc
This one has some is interesting, not sure if it does multi master or not. There are a few projects that seem to do multimaster/collision avoidance, the trick it to find one with low enough overhead and automatically retransmits if there is a failure, and for this project isolates this enough that my sensors doesnt need restructuring.

Good wiring is crucial so you can use higher speeds. The common ground wire in addition to the differential signals seems almost required.

I think you have found most everything that I have. Something akin to csmacd is what I was thinking. Listen, transmit, back off for random time if a collision still happens. Of course full duplex rs485 is another option, hard to find off the shelf modules.

I think this is the library I had found before.
https://github.com/MichaelJonker/HardwareSerialRS485/wiki

@nofox absolutely that is one of the problems. Polling as you describe could be a fix, another is having each node listen before transmitting, there is a (not mysensors) library that does that, CAN bus( a mutli master 485 comaptible bus) is another option. I think that running a common ground to all the rs485 adapters is also wise. This is all in theory as I havent wired up my home yet....

@schlog you might be able to use a modified swr circuit, an arduino could generate a weak forward signal, and then use an analog input to measure the reflected signal ( sort of a TDR) instead of a meter, the impedance match will possibly be bad(maybe even on purpose to enhance the effect), but each type of antenna should be different enough that you can tell both if it is connected, and which antenna it is.

Another thought, if this is permanantly connected, then you should only need to know the positions of the switches for the transmitters and antennas.

Btw My call is:
KC0QWL