In another thread the following was suggested

Posted By: ringiAt least for someone with PV, once local stored energy systems becomes cheaper, the energy should be stored in the home, topped up with PV, and then at time of least demand if not enough PV.

Maybe even sending 12v or 24v direct to all the LED lights without converting to 240v.

So I'm planning a new build, if I had solar panels, just how difficult would it be to have 12 or 24v lighting?

12v lighting is feasible as I did it in my new build, but it was stepped down from 240v rather than battery run.

I did it as I could control the low voltages centrally, and have the 240-12v conversion done in one place which I hoped was more efficient than a large numver of smaller cheaper transformers.

Steve

Yep, most light switches, etc, are likely not rated for DC. Of course, they'll be fine for LED level currents (4 amps+ for 12 V, 50 W halogen might be somewhat different) but as they're not officially rated for DC you might have trouble getting a bright but not quite bright-enough electrician to sign them off.

Aren't there special rules for low voltage lighting making installation (even) more restrictive than for mains? That's on account of the high currents for ELV halogens, etc, but AFAIK not making an exemption for low-current lighting.

Steve, could you tell us more about your 12 V lighting? How it's switched, particularly - e.g., is it 12 V or mains (or something else) at the switches? Does the central 240 V→12 V conversion get switched off when there are no lights on? How?

I would say not worth it unless you were off grid and had batteries anyway.

My lighting is in 2 distinct parts. All are permanently powered so the 240->12v transformers are live all the time , idle power consumption is about 1W for the lot so imperfect but managable.

The control side is all driven by an arduino, so a (5V) digital pin is connected to every lightswitch in the house via normal 1.5mm cable and the arduino senses when the pin is grounded. I used momentary switches to allow for some control options like long presses , short presses, double presses , whatever. Most of this hasn't been implemented yet :)

So the arduino has a memory list of the states of each lighting circuit and adjusts this when switches are pressed. It then has a DMX library and issues DMX commands down a cat5 cable to the "lighting" side

The lighting side is a bunch of DMX 12v 3 channel controllers - permanently powered by the 12V PSUs and connected in daisy chain to the arduino. The arduino, by the magic of DMX can individually turn on or off (or using PWM, dim) any channel on any controller. I have 6 controllers so 18 different lighting circuits on the house, so there is a (1.5mm?) cable from each controller channel to where the lights are.

House is very small footprint and control units are central ,so voltage drop was a concern but not a problem in practice

Will try and draw up a schematic if I get a chance. The arduino runs code I wrote so in theory I can make any button press perform any lighting action - or control remotely over the Internet, etc.

-Steve

Nice system steve - I take it you could write a smartphone app too which would allow you to monitor and control all the lights?

yes, in theory you could control it with a smart phone / web browser. or program a holiday mode that replays the previous week's lighting patterns when you are away. both projects have been on the "to do list" for a couple of years now :) although I have done work on my home energy monitor and heating controller

The only toy I did put in was a "long push" on the main switch in the main bedroom, which turns off all the lights in the house.

Sounds like a nice system. Do you have any backup "dumb" lighting just in case the arduino develops a brain freeze?

Posted By: Ed DaviesA torch?

and candles...

Posted By: SteamyTea

Posted By: snyggapaThe only toy I did put in was a "long push" on the main switch in the main bedroom, which turns off all the lights in the house.

That is a really good feature.
If you extended this concept, you could have a similar system for the ringmain, turns off everything except essentials, such as a fridge.

The problem with this is 240v, which I'm not overly comfortable in dicking about with / creating a solution at this level of bodging.

You can get plug in "remote controllable" plug devices, and control them from an arduino or other device via radio waves, but I suspect these days with modern appliances they use about as much power themselves as the devices that they are designed to turn off..

Doesn't really need to be radio waves, it can work on a line level protocol, even IP which would make it much more flexible. Internet of things anyone? This would really be the killer app for IPv6...

That's neat. So three power supplies each feeding two DMX controllers? I trust you've replaced those CAT5 patch leads between the DMX controllers with ones of more appropriate length. In some ways it might have been more relaxed to make the switch connections be completely separate from the connections for the actual lights - there's only really a single CAT5 between them - but it does give the flexibility to replace it all with a tighter connection in future.

Did you have any problems with noise pick up on the inputs to the Arduino?

Oh how i look back on the old pendant light and switch by the door with fondness

What is the main benefit of low voltage lighting??