DIY LED setup sanity-check

[rusty_roque]

We are in the process of renovating our house, and would like to setup led strip-lighting throughout. of the options, this seems most attractive:

• 12v 120W constant voltage driver powering a bus that routes to each room (optionally 24v 240W, but I think I'll just get two drivers, two busses if 120W isn't enough)
• initially have each led-line be a basic on-off switch
• incrementally add dimming to lines that might benefit by means of a PWM controller
• upgrade the system by signalling the controllers through a smart-home setup (still need to work out the finer details there)

This is the body of my understanding:

• each led has a forward voltage. In a perfect world, a line with a forward voltage that adds to 12, I won't need any current limiting, but if the forward voltage adds to justt 6, I would need something like a resistor to ensure 12v so that the voltage drop across the leds is just 6v.
• I assume constant voltage LED drivers are compatable with pwm-controlled lines. With that said, would it be smart to include some sort of decoupling-capacitor setup so that the PWM controller on one line doesn't introduce too much noise to other lines/driver?
• The ideal voltage is more to do with ensuring that a) all forward-voltage requirements are met so that you don't get dimming/discoloration along your lines and b) you minimise excess gap between forward voltage requirements and provided voltage, so as to minimise current-limiting (which needs extra energy/components) requirements.

Some variables I've considered

• power budget: 100w lines. will get multiple lines if needed
• Type: white strips of varying temp-colors. Will power smart-led projects off of mains.
• no lines pushing the limits of 12v. Will power-inject where needed
• Not so sure about safety requirements. Will be getting a quality driver, will fuses be sensible?
• I'm assuming switch control placement is a minor issue (within reason, of course).

Some other questions:

• what's the limit of DIY work that I can do? Given that I'll be working with just 12v DC (except where hooking up the driver is concerned), does that affect the safety to a significant degree?
• What's an efficient way to drive a short LED strip? using a resistor to limit current seems wasteful, should I instead step-down to 5v on the shorter strips using an efficient buck-converter, for example?
• to what extent can I assume that PWM dimming control on an LED line won't impact other lines/the driver too much? At what pount would I need some sort of decoupling setup?
• I'm struggling to find resources on this approach. It all seems to be "run a constant current driver for each LED-line, and power the driver from mains". It makes sense to have your "lighting mains" just be a clean 12v DC driver-supplied line, rather than having multiple drivers. Am I missing something here?

Thanks in advance

 

[davesparks]

It's a terrible plan, the voltage drop at 12 volts is chronic, you will end up needing massive cables to get 12V over any useful distance.

It's far better to have a driver local to each strip and a short 12V cable.

You don't need to worry about forward voltage etc, that is all dealt with in the design of the 12V LED strip, you just give it a 12V supply and only cut it at the designated points.

 

[rusty_roque]

It's a terrible plan, the voltage drop at 12 volts is chronic, you will end up needing massive cables to get 12V over any useful distance.

It's far better to have a driver local to each strip and a short 12V cable.

You don't need to worry about forward voltage etc, that is all dealt with in the design of the 12V LED strip, you just give it a 12V supply and only cut it at the designated points.

Thanks heaps for that feedback.
So that's probably what I'm missing: 12v is just not enough to be worth distributing. I assumed there would be that trade-off, but if it's really that bad, not worth it...

So that would explain why my idea doesn't have many learning resources online.
Am I on the right track, that If designing a houses electrical system from scratch, the conventional approach is to have a single mains-circuit, intended primarily for lighting? My original thinking was to make this an "LED circuite" Sounds like this should still be the typical mains-line.

With that said, I will probably want more multiple led-lines with separate controls (e.g. two lines of different color-temp right next to each other, and mixing the dimming to get the desired balance). Would parts of my plan still be worth while there? my thinking being is that one CV driver on both a warm and cold-color strip, each in parallel, and each with a pwm controller to mix/dim as desired. no long distances involved. I mean, I could have two CC-drivers, but a single CV driver would be preferable, no?

 

[nicebutdim]

Am I on the right track, that If designing a houses electrical system from scratch, the conventional approach is to have a single mains-circuit, intended primarily for lighting?

I don't know about wiring conventions in France, but modern installations in the UK may have several dedicated lighting circuits. Much would depend on size and layout. A small appartment may have one lighting circuit. A small 3 bedroom house might have two, but equally it might have four. Any of those circuits could have various types of lighting fed from them, (including LED strips most often from dedicated drivers for each area. For example; a kitchen may have some sort of conventional lighting operated from a switch. The next switch might operate under cabinet lighting on two sides of the kitchen, with a separate drivers for each side. The third switch might operate plinth lighting. Maybe a fourth switch operates separate lighting over a dining area.

If this renovation includes rewiring I think the most important issue is ensuring power is brought to every point at which you want it and that due consideration is given to switching and control. The last thing you want after extensive renovations is lighting and controls which appear to have been DIY additions. Get an electrician involved from the outset and explain what you want to achieve. They should be able to accommodate most requirements and should also provide invaluable insight on issues which may not be apparent to you, but will save money and ensure the finished result looks like one might expect.

 

[rusty_roque]

I don't know about wiring conventions in France, but modern installations in the UK may have several dedicated lighting circuits. Much would depend on size and layout. A small appartment may have one lighting circuit. A small 3 bedroom house might have two, but equally it might have four. Any of those circuits could have various LED strips fed from them, most often from dedicated drivers for each area. For example; a kitchen may have some sort of conventional lighting operated from a switch. The next switch might operate under cabinet lighting on two sides of the kitchen, with a separate drivers for each side. The third switch might operate plinth lighting. Maybe a fourth switch operates separate lighting over a dining area.

If this renovation includes rewiring, I think the most important issue is ensuring power is brought to every point at which you want it and that due consideration is given to switching. The last thing you want after extensive renovations is lighting and controls which appear to have been DIY additions. Get an electrician involved from the outset and explain what you want to achieve. They should be able to accommodate most requirements and should also provide invaluable insight on issues which may not be apparent to you, but will save money and ensure the finished result looks like one might expect.

Thanks heaps for the input.

Any of those circuits could have various LED strips fed from them, most often from dedicated drivers for each area.

This seems to be the approach we are gravitating towards.
We've already got a plan for the wiring, and our electrician friend is helping us out. I think the next step is to refine the details of the lighting circuits. I like the idea of a "driver per zone", such as one per (small) room.

The last thing you want after extensive renovations is lighting and controls which appear to have been DIY additions

I'll have to think about that. I'd like to set it up initially so that it's just on-off switches as is tradition, but set up in a way that more complex controlls can be applied behind the panels, for example. I'm a software engineer by trade, and have an interest in developing smart-controls from scratch as a hobby project. I'll have to think carefully on your advice here