Off-grid night-light!

[DamonHD]

Hi,

The kids each have a 0.5W (yes 1/2W!) LED mains plug-in night light, but there is nothing on the upstairs landing and no mains socket even for another plug-in one.

So tonight I've experimentally rigged up a 3W (GU10, cool white) light to stay on all night in the corridor to see how well it works.  It's just one of my desk lights on its over-long lead hung up at the office/bedroom door.

I suspect that 3W is a bit too much light and drain on the system for all night, and my aim is an efficient 1W lamp if I can find one.

Rgds

Damon

[rossw]

So tonight I've experimentally rigged up a 3W (GU10, cool white) light to stay on all night in the corridor to see how well it works.  It's just one of my desk lights on its over-long lead hung up at the office/bedroom door.

I suspect that 3W is a bit too much light and drain on the system for all night, and my aim is an efficient 1W lamp if I can find one.

At my old place we used to have a particularly long and dark hallway, with a set of stairs in the middle. Kinda dangerous for the odd guests we had.
I got a cheap pack of white LEDs off ebay (I think they were only 20,000 mcd). I ran a single run of thin figure-8 wire (Bell-wire I think much of the world knows it as, or "mini speaker flex"). Every couple of metres along its length I would cut one conductor and solder a white LED. I ended up with 6 or 8 LEDs along the length of it. With both ends shorted, it was easy to feed it with power part way along the length where there happened to be a convenient access point. I used a very small 24V plugpack, and a single current limiting resistor. I fiddled with the resistance until the string took about 5mA

It made enough light to navigate by, but not enough to ever be annoying. More like moonlight. Worked for several years and drew so little current that the LEDs worked for quite some time after the plugpack was turned off. Might be worth a try?

[Tritium]

I have used "lime-lites" for years (at least 45). Almost no current draw at all. They are electroluminescent panels about 2" by 2" that plug directly into a wall socket. Not off grid though. There are now battery powered electroluminescent ropes and wire available on fee-bay.

Thurmond

[DamonHD]

Good ideas, thanks.  Will bear them in mind when visiting Maplin today!  B^>

Rgds

Damon

[Simen]

I have some red 10mm clear leds embedded in my ceiling as night light. They doesn't use much power, and give me enough light to light up my path to the toilet and doesn't ruin my night vision.

[DamonHD]

Does red work well?

Rgds

Damon

[ruddycrazy]

The led's in my shed that provide night lights are on 24/7 and have been for near 4 years now. All I did was use Amanda's circuit and the power is off my 16 volt nife array, several of them are 550,000 mcd which I got off ebay and put them in old solar reflectors cause if you look at them straight on you'll have a headache for 3 days. Although they don't provide enough for direct lighting they do provide a light to get to the smart relay device I use to turn everything on. All the nife bank has is a 80 watt pv panel to charge off and only several times in the time I've had those free nife batteries have they shown less than 3 volts. That was when I left some 12 volt cfl's on that have since died out. All in all just use Amanda's ciruit for long term use as it works for me and that Master Class on LED's was worth the world to me. Hell why hasn't the mod's on this forum make the full Master Class a sticky in the lighting thread is beyond me.

[DamonHD]

Dig me out that thread and I may just make it a sticky!  Thanks!

Damon

[ruddycrazy]

Damon this might be a job for da local houndog 'da Woofer' that guy can sniff any thread form the old board and I do reckon that 'master class' is worthy of sticky status all 4 or 5 parts of it....

Regards Bryan

[DamonHD]

Thanks for the suggestions everyone.  I took several of them on board...

I had another attempt on 100th the power input using NiMH rechargeables so the nightlight would not need to be wired in (at the suggestion of my SO).

This is using one of the grab-bag that Thurmond sent me for tinkering with (thanks again!) and is simply 4x1.2V NiMH driving the nominal-3.5V LED via a 470R resistor (which would give over a month's use with 2000mAh cells), which I might drop to 100R if we need it brighter.



http://www.earth.org.uk/LED-lighting.html#homebrew-nightlight

Rgds

Damon

[Simen]

Does red work well?

They doesn't make the room bright by any means, and if you come from a brightly lit room into a dark room lit only by these red leds, you wouldn't even notice them. But when your eyes are used to the dark, there's no problem seeing what's in the room. Red light are a normal color in map-lights onboard boats/ships, because it doesn't ruin your night vision.

The leds i'm using are 1,8V, 20mA, 5000mcd, and makes a 75-90cm circle of light at 2m distance.

[ghurd]

The room color will have a great effect on how certain color LEDs work for night lights.
Yellow LEDs in a blue room do not do much good.
G-
(posted with an iPad, just playing)

[DamonHD]

(G! You've come to the dark side: posted from a Mac!)

[zap]

Commanda's "LED Master Class" links

#1
http://www.fieldlines.com/board/index.php/topic,131213.html

#2
http://www.fieldlines.com/board/index.php/topic,131214.html

#3
http://www.fieldlines.com/board/index.php/topic,131215.html

#4
http://www.fieldlines.com/board/index.php/topic,131296.html

#5
http://www.fieldlines.com/board/index.php/topic,131217.html

[ghurd]

(G! You've come to the dark side: posted from a Mac!)

Just visiting!
G-

[wooferhound]

Zap beat me to it . . .
I have been very busy for that last few days so I am just getting around to reading this
Commanda's LED Master Class along with a few more LED lighting articles is in the FAQs area with the title of
How Do I Make My Own LED Lights
http://fieldlines.com/board/index.php/topic,143569.0.html

[DamonHD]

Thanks, I've pinned yours up too for now...

Rgds

Damon

[DamonHD]

With the addition of a SPU30P06P P-channel power MOSFET (that I had to hand), a SFH300-3 phototransistor pull-up gate to source and a 1MΩ pull-down resistor I get a nightlight that goes off automatically in the light!

Have to see if it turns off properly in its gloomy corner in the day...

I've done this mainly to make the batteries last longer between charges, and because I can...  B^>

If this scheme works then I'll repeat it with some amazingly efficient LEDs that ghurd sent me (thanks)!

(Have I said how wonderful it is to work 3 days a week 5 minutes from a bricks-and-mortar electronics retailer, and 10 minutes away from a different branch the rest of the week?)

Rgds

Damon

[ChrisOlson]

The kids each have a 0.5W (yes 1/2W!) LED mains plug-in night light, but there is nothing on the upstairs landing and no mains socket even for

We got some .3 watt LED night lights in a four pack for $4.99 at Menards.  They have light sensors in them so they turn off by themselves during daytime and if the big lights are turned on.  We got one in the garage, one in the hallway, one in the bathroom, and a spare.  We're off-grid and my system can't even tell they're there when they're on because the inverter is in idle mode with the line voltage at only 90 volts and those little LED night lites work fine on that.
--
Chris

[DamonHD]

The children's nightlight have those sensors too, to turn off when the room is light, but I can't actually detect any drop in the power drawn when that happens!

Rgds

Damon

[ghurd]

Related to AA powered:
It has been a while since I went through everything commonly available, or commonly available here.
The only motion sensor night lights I recall that save any noticable power when off are the type with the daytime sensor.

And the best versions had a few primary issues, when related to LEDs.
#1-  The 3-way (On/Off/Auto) switch had a different voltage to the bulb when in Auto than On.  1V is a pretty serious difference when starting with 6V max, and a white 3.2V LED.
#2-  The bulb socket could have been wired either polarity.
#3-  A large percentage did not work from the factory, and that was when I was purchasing them direct in very large quantities.
#4-  The better ones cost a lot more than the cheapies, but its not really possible to tell which expensive one is good until after you bought it.
#5-  The company(s) I delbt with have taken to going with the lowest Chinese based bidder, and the PCBs and circuitry are not the same from one batch to the next.
#6-  The factory made versions are less costly than they used to be, and there is a reason for that.

Wow.
Looks like more than a few reasons.

(back to VISTA)   
G-

[ChrisOlson]

The children's nightlight have those sensors too, to turn off when the room is light, but I can't actually detect any drop in the power drawn when that happens!

Well, I'll put it a different way - my off-grid system is 12 volt and the inverter that powers the house circuits draws .67 amps @ 12 volts nominal in idle mode, or 8 watts.  With all three of those night lights plugged in and glowing, and nothing else running, the inverter runs the night lights and still draws the same .67 amps.  Ultimately, I suppose it's still a .9 watt draw on my system, but I've never been able to detect that it makes any difference in the big picture.

My AIMS off-grid inverters drop their voltage down to 90 volts in idle mode and I suppose part of the 8 watts it draws in idle is used to keep the line alive to detect a load sufficient enough for it to raise the voltage to the rated 120.

Any inverter is zero percent efficient at zero load because they consume power from the battery bank doing nothing but keeping themselve alive waiting for a load.  The dual 3 kW AIMS inverters I have seem to be able to run up to a 5 watt AC load without consuming any extra power above idle consumption.  At 6-7 watts load they detect it, raise the line voltage to 118-120 and then start drawing more power from the battery bank.

So I pretty much consider those little LED night lights to be "free" as far as power consumption.
--
Chris

[DamonHD]

Finally drew up my little NiMH-powered portable night-light circuit diagram:



Rgds

Damon

[DamonHD]

With a 470R resistor in series with the LED and a whopping 12mW of power to the LED, the nightlight has been ruled "too bright" and was being partly covered/shaded!  So I've cranked up the resistor to 4K7, yep, something a little over 1mW into the LED and maybe just maybe as much as 0.5mW out.  Let's see if this is still too bright!

At the 1mW consumption and given the auto-off circuit when there is enough light around, this should in theory last an entire winter (just about) on the battery it's using, but the cells would probably self-discharge faster!

Rgds

Damon

[Fused]

Ive learned from the Guru the importance and usefulness of under powering LED lights.
I also just learned that overpowering a LED lasts only seconds. 

Cool way to devise a night light to run on a battery that should last months at a time.

Do you think a 10mm white LED is too much for this kind of application?


Fused

[DamonHD]

Don't go confusing me with an expert: that would be an error!

The LED in this is ummmmm 10mm I think but I can't even find a ruler...

I suspect that it's very efficient (lm/W) at this very low drive, but might be rather wasting the $$$ spent on the LED if I'd actually paid for it.  But as Thurmond sent it to me gratis, the price is just right as-is.

So really, if you've got a 10mm LED that does the job and hasn't got a better use then it's not too much?

Rgds

Damon

[Fused]

Lol DamonHD, I was referring to the brightness of the 10mm LED vs the 5mm standard LED.
I couldn't figure  what size LED you were using, is all.

Thanks
Fused

[dnix71]

Here's my led night light. I bought it at Home Depot to light the corner of the outside wall. It comes with 3 AA nicads. It failed from corrosion at the battery contacts. The nicads were fine. The small solar cell still works, too, but I disconnected it.

Since it didn't put out much light anyway I brought it indoors and mounted it over my laptop. It provides enough light to avoid tripping over things but not enough to keep me awake at night. It's plugged into the 4.5 volt tap of a Harbor Freight "controller" that comes with the 45 watt kit.

The light sensor can be aimed and is instant on/off. It doesn't pull my batteries down any that I can detect.

[ghurd]

10mm is a marketing ploy!  10mm sounds better than 5mm, so people buy them.
Typical 10mm LEDs from surplus and hobby suppliers are no brighter or more powerful than 3mm or 5mm LEDs.
In fact, most of the 10mm I see for sale in the catalogs are nowhere near as "bright" (meaning the total light they make is less) as a decent regular old 5mm LED.

Damon,
Did you get a chance to play with the ones I sent?
G-

[DamonHD]

G: yes I have had a play, but was diverted for various reasons including revocation of my permit to install an extra night-light downstairs after I found an old plug-in LED nightlight as a temporary test.  Bv<

But I intend to deploy them in some sensible way!  Thanks again for them.

Rgds

Damon

[DamonHD]

Still going strong on its mid-December charge...  Battery voltage 4.86V so still 'nominal' Voc!

We've had plenty of days dark enough for this thing never to auto-off.

Rgds

Damon

[Bruce S]

Still going strong on its mid-December charge...  Battery voltage 4.86V so still 'nominal' Voc!

We've had plenty of days dark enough for this thing never to auto-off.

Rgds

Damon

Damon;
   That's good to see/read. As the impending ice storms looms towards St. Louis,MO. I fear we will get yet another chance to try out the 3 watter Rich & I installed in Philippines.

In our on-grid house I currently have two separate PV setups the bigger ready with coffee pot. The other smaller set for lights on 1st floor is set for CFL and LED lights only so we don't step on the ultra-black door guard  .


Both sets will, depending on outage time will be testing the NiCd banks.
Have fun!
Bruce S
 

[DamonHD]

Well, here's hoping yours works if you need it!

I'm still amazed by how useful milliwatts of light is in practice compared to say the kilowatts needed to do significant heating.

Rgds

Damon