Designing Whole house LED night lights.

[Bughunter]

Yup, 48v seems to be am old telecom standard. An electrician friend gave me
his old copy of the NEC code book. I can always dig into that, but I'm sure
you are correct.

 

[JoeSP]

The recent discussion about LED lighting included a couple comments on the
appropriateness of LEDS for night lights. I thought it was an idea worthy
of it's own thread.

My off grid home is in the stage of construction where the interior walls
are still open accessible to add wiring runs. So, now is an opportune time
for me to add wiring to the whole house. So far, I have not installed any
low voltage wiring runs, just the 115vac wring typical of a standard US
home.

I have been casually thinking about adding a dedicated low voltage DC
circuit to support some LED night lights as a simple aid to night
navigation. I have a few ideas, but have not made any decisions yet. Maybe
I can get some ideas here to influence me in one direction or another.

I'm interested in ideas on how I might set up LED night lights throughout
the house.
Right now, I use a few glass enclosed tea candles for night lights which
is romantic, but a little too 19th century. I want something that looks
professional, and not homemade.

My inverter runs in sleep mode at night, so I'd prefer a solution that
does not require 115vac except perhaps for periodic (and hopefully
infrequent) manual battery recharging.

I wonder if it would make sense to power the LED night lights from my main
48v battery bank, or to use a separate dedicated bank, and maybe at a
different voltage?

My main bank runs at 48v. I suppose it would be easy enough to run a
dedicated, fused, 48v wiring run..With a 48v run, I would not have as much
voltage drop across the wire and could use smaller gauge wire. But, would
I be just burning it off in resistors required to drop the voltage to that
required by the LEDs?

Alternatively, I could setup a separate 6v (or 12v) deep cycle golf cart
battery. This would require periodic recharging, probably with an
inexpensive automotive charger plugged into my 110vac. I'd almost prefer
not to go this route, because it adds one more thing separate subsystem to
have to monitor and maintain. On the other hand, if it were 12v, then I
might find it useful for other non-nightlight applications such as
recharging my cell phone where 12v is the more common voltage. DC to DC
converters are somewhat pricey, but I suppose for one or two low draw
outlets it is a possibility.

I am thinking that a single switch per floor would be adequate for my
place. I wonder if I could just use a normal 110vac light switch for
48VDC, or I would need a DC rated switch?

It would be nice if I could use some small gauge wire, like Cat5, or door
bell wire. Each wire run might be in the range of 100 feet per floor.

My place is 2200 square feet, on two floors. I think 6 to 8 night-lights
fixtures per floor would provide adequate night lighting.

Is a single led per fixture adequate? Color?

Are there any off the shelf low voltage DC fixtures that might be
applicable. I don't want to reinvent the wheel if an off the shelf
solution exists, as long as it is no too expensive.

I wonder what kind of fixture could be made that would be simple to
construct, yet
not look homemade. One thought is to use a single outlet type mounting
box, and use a blank switch plate mount a led. Maybe more than one led per
plate?

Ideas? Experiences? Links? Calculations?

LED house lighting is still in its infancy. It may turn out to be a big
mistake to commit to one type of wiring at this stage. We do not know which
formats will emerge as those that stay. I suggest running wires that allow
for flexibility in voltages. The fixtures can be changed over the years, but
the wiring is a different story. Stick to the minimum specs required for a
wide range of options.

By the very nature of white LED lighting, we know that there is much room
for improved efficiency and the ability to tune the wavelengths by altering
the mix of red, blue and green. Tomorrow's dimmer switch may not only allow
us to lower the light level, but to adjust the colors, shades and hues of
the room lighting as well. Stay tuned.

 

[Steve Spence]

Steve Spence wrote:




There are also the cold cathode fluorescent stuff. Widely used for
making your car very flashy and stupid looking. Available in different
colors and forms at Walmart, runs on 12 VDC. I have no idea
how efficient they are.

--Dale

Pretty efficient.

 

[Antipodean Bucket Farmer]

We don't have any night lights and have never felt the need for any.
If the route to the bathroom is perilous, you could add switches near
the bed to turn on a distant light sufficient to show the way. Or put
a small flashlight on a table next to the bed. As for the occasional
roam around the house at night without waking others, I find that the
twinkle of LEDs on miscellaneous appliances provides orientation. ;-)

I use a battery-powered (4 x AA plus an input for 6v
from a wall wart, etc) light with a motion detector.
Switchable to light either a regular torch type bulb,
or a circle of white LEDs. It is in the hallway
between the bedroom and bathroom. Can be turned on at
night and off in the morning.

NZ$25 from The Warehouse (equivalent to Wal-Mart.)
Seems that one might be DIY-built at slightly lower
cost, with one of those motion sensors sold for modular
burglar alarm systems.

Also good in case of a power outage.

Another idea would be wireless remote control next to
the bed, to avoid installation of wired switches (e.g.
in a rented apartment.)

 

[George Ghio]

But, I don't think I'd need 16 LEDs for a single night-light. I'm thinking
that 1-3 might be
enough (light-wise) for each fixture. I don't think that I want to run
series strings in the walls although it would be possible. It feels a little
like those series strings of xmas lights, where you had to search for the
bad bulb to fix a string. With the long life of LEDs, it would much less of
a problem. Maybe it does make more sense to just use 16 leds and get more
light rather than just disipating the power in resistors as heat.

Well I wouldn't do it, but it is a consideration if it might suit the
needs.

Then again, for a whole house night light, one at each end of a hall,
top and bottom of stairs...

I was also thinking that a standard 10A ac switch would do the job.
I doubt that arcing would be a problem.




Not a bad idea. I'd consider it.





I am mainly focused here on night lights, meaning a few low intensity lights
spaced to aid in
navigtation. For my more general lighting needs, I use 115v compact
flourecents, and standard 115vac fixtures.





Agreed. I use no incandecents at all. Typically, I will have no more than 3
CFL's on at a time.





I am planning on a breakfast bar. Several nice looking recessed fixtures
would be cool. That might be a good candidate for some multiple white led
lights instead of CFL's.

The best thing is to try your lights while you can still move them
around. I had lights in a bare frame for months. I would go and try them
at night, walk around, sit in a chair to read, whatever. Moved some of
the lights several times to get the right spot for the fixture.

Tried different types of lights in a number of places to see what worked
or in a number of cases what didn't before running the cable.

 

[Ecnerwal]

They require 120vac. We lost 4 of them before switching to LED nightlights.

I have two dead flat plate lights here. Less than a year of useful life
- I think the material might be "fine" but the contact between the
material and the plug seems to be busted and not fixable - without any
particular abuse at all (ie, plugged in left alone - not repeatedly
plugged and unplugged or beaten on in any way - just stopped lighting
up. I have watches with 5 times that life on them that still light up.)

Don't waste your money on those...

 

[Ecnerwal]

Now I wonder what their salesman will tell me when I ask for 5 of em?

See if either

www.digikey.com

www.mouser.com

stock them - they are both happy to sell you one, 10, 100 or 10000 (at
different prices) of various things, though they might have a minimum
order (but not a large one, and easy enough if you put your shopping hat
on - grab some LEDs and switches, for instance).

OK, I looked - Mouser has them - $0.70 for 1,$0.52/ea for 1000.

Well, actually there seem to be several options among Supertex CL2,
probably related to package (ie, tiny surface mount or more useful to
normal humans leads), and I'm not looking into it in detail as I need to
get to sleep, but somewhere in that ballpark, and I'm not quickly
finding a minimum order amount, but have certainly placed small orders
there in the past, so it can't be too obnoxious.

 

[Bughunter]

See if either

www.digikey.com

www.mouser.com

stock them - they are both happy to sell you one, 10, 100 or 10000 (at
different prices) of various things, though they might have a minimum
order (but not a large one, and easy enough if you put your shopping hat
on - grab some LEDs and switches, for instance).

OK, I looked - Mouser has them - $0.70 for 1,$0.52/ea for 1000.

Well, actually there seem to be several options among Supertex CL2,
probably related to package (ie, tiny surface mount or more useful to
normal humans leads), and I'm not looking into it in detail as I need to
get to sleep, but somewhere in that ballpark, and I'm not quickly
finding a minimum order amount, but have certainly placed small orders
there in the past, so it can't be too obnoxious.

Thanks for the link.

I can handle $.70 a piece for a couple of them. Yes, they do come in several
packaging styles. I didn't see anything about a minimum order either, but
there may be one hidden in the checkout. I'll give them a try.

 

[Steve Spence]

Bughunter wrote:




Do it. Now is the time to install a bundle of LV wiring for whaetevr
future uses come along. Lighting, alt power, zoned temp control,
security, data comms, remote control, and who knows what will become
useful in future. Running cat5 is very cheap, and it would be a lost
oportunity not to run it, even if you dont have a specific use right
now. Its very cheap to run it, and difficult to put in later. You'll
likely regret it if you dont.

2x or 3x Cat5 is good because its the leading standard and its
adaptable. Multicore burglar alarm wiring is also useful.

Cat5 cable can't handle much load at 12vdc. It's 24 gauge, and too light
weight. I wouldn't run more than an amp over a 10' distance, too much
voltage drop.

 

[P. Lyttle]

Cat5 cable can't handle much load at 12vdc. It's 24 gauge, and too light
weight. I wouldn't run more than an amp over a 10' distance, too much
voltage drop.

A white superbright runs at 20 mA max. Three in series (10V) plus 100 Ohm
resistance (some of that may be from the cable) goes quite adequate over cat5.
A superbright is more expensive, but you save on cabling (and battery drain)

In many lighting applications it might be beneficial to remove the lens molded
on the LED either by cutting, grinding or sanding (I use a lathe) with the
front polished to reduce backscatter.
This provides a remarkebly bright ambient light.
One of these illuminates my attic, another the sccond floor and staircase.
the third of the triplet is projected in my living room.
I will probably install a second triplet, but just those 6 leds will provide
all the emergency lighting I will need, using cat5, at a 30 mA drain.

As a fiture I use the standard black plastic mounting rings, which will
push-fit in a 6.5 mm hole, like these:
http://www1.nl2.conrad.com/m/1000_1999/1800/1850/1859/185914_RB_00_FB.EPS.jpg
The wire goes in the back

P. Lyttle

 

[William P.N. Smith]

The recent discussion about LED lighting included a couple comments on the
appropriateness of LEDS for night lights. I thought it was an idea worthy of
it's own thread.

I guess it is! I'd look at boat stores for 12V LED lights in
fixtures, though they may be too expensive and/or too flimsy for what
you are looking for. I wandered around a boat store a number of times
looking for just this kind of thing, and was pretty underimpressed.
Catalogs and WWWebsites can be deceiving, you'll want to see them in
person.

The other option is LumiLeds Star 1W emitters driven at maybe 100 mA
and mounted in a standard electric box in the ceiling.

I just keep an LED flashllight by the bed.

 

[William P.N. Smith]

Well if we say each LED needs 3V then 16 leds in series would use 48V.
No resistors.

Well, George would say that, but as always he'd be wrong. Never drive
an LED without some kind of current limiting.

 

[Bughunter]

I guess it is! I'd look at boat stores for 12V LED lights in
fixtures, though they may be too expensive and/or too flimsy for what
you are looking for. I wandered around a boat store a number of times
looking for just this kind of thing, and was pretty underimpressed.
Catalogs and WWWebsites can be deceiving, you'll want to see them in
person.

The other option is LumiLeds Star 1W emitters driven at maybe 100 mA
and mounted in a standard electric box in the ceiling.

I just keep an LED flashllight by the bed.

I try to keep a hand cranked dynamo led flashlights on each bedstand, but
they have a tendency to wonder off to do other chores.

I guess I am trying to get a little bit of a "gee-wiz effect" as well. I
have a lot of fun explaining to visitors how my off-grid house power system
works, and evangelizing about the benefits of extreme conservation. A string
of led night lights would be one more topic of conversation, as well as
serving a useful purpose.

There have been some great ideas here as I new there would be. I believe
that I'll collect a few components and have an interesting little project to
do on my next prolonged visit to the house.

 

[George Ghio]

Never wrong mate. 16 Leds in series would run off 48 volts. BUT as the
charge voltage could reach 60 volts... Well you can see that there is
more to the problem. The whole idea is though that thinking differently
can, and does, solve many problems.

The main point is that Bughunter is at a point where he can play with
the placement and configuration of his lighting before he locks himself
into the usual "Light in the middle of the room" syndrome. No matter
what voltage he wants to use.

Wiring a bare frame is a lot easier than retro fitting after the dry
wall is up.

It is quite possible to double or triple the number of lights used and
still reduce the energy requirement needed for lighting significantly by
placing lights to their best effect for given lumen output.

 

[Vaughn]

Never wrong mate. 16 Leds in series would run off 48 volts.

No George, I respectfully think you are wrong this time. I would never
connect Leds to any low impedance source without current limiting. A common
failure mode of any solid state device is a short circuit. If you develop a few
shorted Leds in a string, or if you happen to get the wiring wrong...
Well...you get the picture.

A possible exception is certain Leds that I have seen packaged with some
type of internal regulation/current limiting inside the package.

Vaughn

 

[Ecnerwal]

each lighting point uses 20mA. Lets say 4 rooms per floor, thats 160mA
total

If running from 48V with a current-limiting driver such as the Supertex
that was mentioned, 20mA will probably run _all_ the night lights, if
they are put in series. Thus, no trouble at all on Cat 5. With typical
red, green or amber LEDs you should be able to run 20 or so in series
off that supply voltage. Most whites & blues appear to need higher
operating voltage, meaning less LEDs in a single string. Drawing 20mA
per LED is wasteful, especially with 48V available, and simple
regulating parts for it also available.

 

[George Ghio]

The fact that all I proposed was a concept, not a complete circuit, does
not make me wrong. There are several technical issues that would need to
be addressed. Not the least of which is the fact that the battery bank
could reach 60 volts with enough amps to vaporise the wiring. Current
limiting is required, yes. A fuse would be handy as well.

But the concept is a possible one.

 

[George Ghio]

They /can/ be run like that, but no-one that knows anything about them
would recommend it, even as a temporary lash-up.

NT

You are only repeating what I said.

 

[Vaughn]

The fact that all I proposed was a concept, not a complete circuit, does not
make me wrong. There are several technical issues that would need to be
addressed. Not the least of which is the fact that the battery bank could
reach 60 volts with enough amps to vaporise the wiring. Current limiting is
required, yes. A fuse would be handy as well.

But the concept is a possible one.

Of course! Operating LEDs without the slightest current limiting was just
a faulty "concept", not necessarily a complete faulty circuit, so you are not
completly wrong.

Vaughn (why did I bother?)

 

[Ecnerwal]

Vaughn (why did I bother?)

Or more to the point, why isn't GG in your kill filter? He earned a
place in mine...I do wish the rest of you wouldn't feed him, it just
keeps him hanging around.