Distributed Power vs Centralized Nodes

[brendanl]

I currently have several sensors throughout the house collecting information and controlling various things. All the sensors to date have been independently powered where they are located.

I’m now thinking of dropping some relays in walls and perhaps some low power lighting and am contemplating the following approaches to distribution:

• Nodes continue to be independently powered where they are located. Pro is isolation, con is more 240v to 5v convertors and needing to put these somewhere (in wall etc).
• I run a single 5v or perhaps a 12v wire around the attic and power the distributed nodes from this. Pro is less 240v convertors & safe distributed power levels, con is potential voltage and current supply issues as node numbers increase. Perhaps I distribute 48v to compensate?
• Nodes are centralised somewhere and only the feed to the relays etc are distributed. Pros are easier to scale power requirements (add more transformers in one place) & easier to re-flash arduinos if necessary (I’m not using OTA). Cons is fiddly build to make it look and function nice and more wires being distributed everywhere in the attic. And does centralising nodes complement or contradict the MySensor mesh network approach??

Appreciate people’s thoughts and their own experiences. And if anyone has seen some nice gear that would help with any of the builds, I would be interested. Otherwise it’s cellotape for the wires and pieces of wood to make a box

[mfalkvidd]

If you haven't seen it already, @petewill has a great video in https://forum.mysensors.org/post/46658

[wallyllama]

Use adequately sized wire to make sure you dont have too much voltage drop. There are calculators all over the 'net.

If you have some particularly long runs, consider dividing the nodes between two ( or more) centralized power supplies. It is a compromise, but may be a good one.

[brendanl]

Thanks guys for the info. In addition to distributing the power to the remote nodes, what do people think about centralizing the nodes and only spreading out the wires to the sensors/actuators? Again, voltage drop could be an issue, but I'm more thinking about the 'concept' of centralizing components of the mesh network vs distributing. It sounds contradictory and I fully appreciate different approaches to different needs etc. I guess I'm perhaps after theoretical feedback?

[wallyllama]

TL;DR. To me the history of computing is the story of centralizng vs. decentralizing. As a "peripheral" becomes more powerful it becomes a center, that is then decentralized from....

Centralized

Pros
cheap at the edge, center can more easily share resources (economy of scale), one upgrade can improve the whole system.

Cons
edge is less flexible, sharing resources can lead to contention, center is more complex and possibly harder to troubleshoot. Probably more wires between edge and center.

Decentralized

Pros
nodes are more flexible and easily adapted and customized to the location, smart nodes can respond faster as it doesnt have to travel all the way to the center, wait for attention, then go back (like reflexes, they only have to travel to the spune, not to the brain). A single failure is less likely to take down the whole system. Can probably use radio in place of wires.

Cons
probably more expensive overall, more points of failure, network to center is probably more complicated, required better wiring.

My personal preference is hierarchical. I like nodes that can operate independantly if disconnected, hubs that aggregate and do some processing (like a spine), and a center that has the big view and uses all the inputs to make big decisions. Call me biased if you will, but it is just the way I am made. :c

[petewill]

If you are putting lighting in your house that will replace normal lighting (not accent/supplemental lighting) I highly recommend that you design it so it functions if there is 110/220 going to the switch. If it relies on another power supply to switch it on/off you can have safety issues if your whole house power supply goes out. That being said I have nodes all over my house that are powered from one power supply. These nodes are not critical to my house's function and it really doesn't matter if everything stops working (although it would be inconvenient).

[brendanl]

@wallyllama Nice answer - thanks very much.

I'm going to go with a central power distribution point and send out 12v to any nodes that need powering. Each node will have a buck and drop whatever voltage they receive by that point, down to 5v. This way I avoid any voltage drop issues that could occur.

It also gives me a single & scalable power source location and nodes close to their activity & still fulfilling their mesh roles and responsibilities!

I like the @petewill setup, but will probably establish it using something like these: https://www.aliexpress.com/item/Free-shipping-1pcs-9-road-output-switching-power-supply-wiring-board-current-shunt-board-wit-fuse/693330771.html

I was also thinking of going one step further with something like: https://www.aliexpress.com/item/9CH-DC-12V-15A-Switching-Power-Supply-With-Box-180W-Monitor-Camera-12V-Power-Transformer/32602759262.html but I'm not sure just how much to trust these? At least with just the first distribution board, I can power it with some old wall-worts initially (appreciate less power capacity). If anyone has anything good to say about the aliexpress switching power supplies, I may still consider.

Cheers