So, the answers are:
No audible alarm in the unit itself. Instead, it contacts you via either the phone app, by email, by texting, or by telephone if it detects a fault.
If a fault is detected, it guides you into finding out where it is. If you're not able to locate the fault yourself, then Ting says it will pay up to $1000 for an electrician to find the fault, perhaps depending on what fault it thinks it detects.
At the sensor level, it monitors house voltage in real time, and keeps track of the high and the low for each day. It says that can be relevant if the transformer feeding your house from the utility is near a failure point, in which case it can alert you to contact the utility. It also monitors high frequency activity on the electrical system, which is what it uses to detect arcing.
Honestly, I'm not expecting it will ever actually detect a meaningful problem, but who knows? It was free from my insurance company, and so I presume they did a due-diligence analysis and concluded that the risk reduction justified their cost of buying and distributing it to their customers. If nothing else, the power monitoring might be useful in logging brownouts and over-voltages on the mains: if a server or other device goes wonky, I guess I could see whether it correlates to a voltage fluctuation on the mains. If there is a home assistant interface for it, then perhaps I could log all the real-time data using that and use grafana to graph it. That might be interesting data to review if a fault were ever detected.
@ejlane said in Completely lost about multiple door switches/lights/sensors:
I wouldn't even bother with an Arduino/microcontroller at all for this. Just some diodes on each circuit and maybe some transistors for powering the large LED strips, or could also use tiny relays.
But I don't see where it has anything nearly complicated enough to have code running on a chip to run anything on it. @itjobhunter if this is not helpful and you need more specific details and/or a quick napkin sketch I can throw something together to show what I'm trying to say.
I think you are right. I really was just lost on how/where to start on building my solution, and someone suggest Arduino. I googled it, since I had no idea what it was, and MySensors was one of the search results with the best information and most knowledgeable members. I'll take your advice and work on an electrical solution as opposed to something more complex. I appreciate EVERYONE'S comments, and steering me in the right direction!
Lots of info here: https://forum.mysensors.org/topic/8735/cnc-pcb-milling?_=1624294898545 It's as close as you'll find to a complete walkthru.
Turnaround is faster than JLPCB (an hour vs days). Otherwise, I would agree. TL;DR: for rapid iteration, or you simply want something fast, DIY PCB's are hard to beat.
As to topicality, it's a subject not covered well on most other forums. CNC Zone has some posts, but that's about it.
All in all, the tools keep getting better, and it's easier now than before to find speciallized bits that make the work easier.