Blue LED night lites from the Dollar Store

[Andy]

Andy writes: I recently bought some blue LED nite lights from our local Dollar Store ( for $1 USD each ) and find that , while they don't give out as much light as the 5 or 7 watt nitelights I have been using, they are perfectly adequate for keeping me from stumping my toe on the dresser on the way to the bathroom at 2 am......

They are advertised to draw only 0.4 watts ... That would mean if plugged in 24 hours a day, they would cost me only

35 cents a year ( 10 cents per kwh ) . I kind of like that...

So I took one apart and made a schematic. The limiting is done by a series capacitor.... I then fed the network into a PSPICE simulator and checked out the claim..... Truly, it uses only 0.4 watts of real power.....

I went back and bought a sackfull..... If anyone else has experience with these items, please post your experience....

Sure, the light is weird ( kind of cool, actually ) and it is only useful if you have been in a dark room for a few minutes, but that is nomally the case for our household.....

Andy in Eureka, P.E.

PS If anyone is interested, I can Email you the schematic.....

[Han]

Andy wrote in news:23d7405e-fe98-48eb-9a60- [e-mail]:

Can't find a link for the darn luminescent night light we have had going for more than 20 years. It is a 2" diameter flat disc in a very thin housing that glows blueish/tealish at night. The info on it is Intermatic Inc, GN GOOD NITE LITE, E 187141, Model GN141, UL listed 8G25 and ML-003, Made in Taiwan.

[Andy]

Andy comments,

Han, I have seen those electroluminscent lights... The blue LED puts out a lot more light.... If you like your electros, you would LOVE the blue LEDs..... I don't know the power your electro uses, but I'm sure it is quite small.... I have used that technology for backlighting displays in the past..... I found that they are great for marking a place on the wall, but don't put a lot of light out into the room to avoid stepping on the grandaughter's roller skate in the middle of the hallway... .... :>)))))

Thanks for the reply.

Andy in Eureka , P.E.

[Tony Hwang]

Hi, Limiting by series capacitor? Prices of those will come down further with time for sure.

[Han]

Andy wrote in news: [e-mail]:

You're welcome, Andy. We just use it to reference the toiletseat ....

[hrhofmann]

A small capacitor will have a very high resistance (Impedance) at 60 Hz, so it is effective. The LED probably only needs about 50 - 100 milliamperes, and no power is lost in the capacitor, so everything works great.

[krw]

I've been using them (well, not from the dollar store) for three years. I like them a lot. I have other colors, too.

Sure.

[krw]

100mA would be about .3-.4W dissipated by the diode (Vf=3-4V @100mA), so you're in the ballpark.

[George]

You had much better luck than me. We had at least 4 different versions of the type of night light you described. All slowly burned out block by block. I replaced them with the LED versions.

[Andy]

Andy comments:

Yeah.. It seems that the power factor shift ( around 80 deg from memory, but don't hold me to it ) means that the power is reactive, and doesn't register on the TXU meter..... That's how I figured it ...

Andy in Eureka, PE

[Andy]

Andy replies: The "reply to author" in my browser gives crap for your Email.... So, I can send it to you in a PSPICE schematics file, or I'll write out a "descriptive" file in .txt for you to use.. But I need to know where to send it ...

Andy in Eureka, P.E.

[Andy]

Andy comments:

A privelege to hear from someone who understands the subject ...

Andy in Eureka, P.E.

[Andy]

Andy comments:

I appreciate the fact that you know what I am talking about, but if you add up the parts in the $1 USD nitelight, I really don't see how it can be manufactured/distributed/retail markup much cheaper....... I don't mind $1 USD ....... :>)))

Andy in Eureka, P.E.

[Andy]

Andy comments:

PSPICE says around 20 ma peak.......(from memory) and the powerfactor around 80% or so ( also from memory)

Run it youownself to check...... regular PSPICE ....

If you can buy one and dismantle it, it is very easy.... Or, send me an email address and I'll send you a schematic file....

Andy in Eureka, P.E.

[Home Guy]

Your typical high-brightness white LED can be powered to full brightness by applying about 3.0 volts and maybe 25 milli-amps max. That works out to 0.075 watts. You can buy high-brightness white LED's from Digikey for anywhere from 10 to 25 cents each.

I don't know why or how your blue LED would draw 400 milliwatts. That's crazy, unless there are 4 or 5 LED's in each unit.

You should just go with the cheap white LED's. They give off a more natural light vs those blue ones.

[G. Morgan]

You don't have to type your own name...

That sounds about right.

Sweet.

Awesome man.

You must be retired, you have w-a-y too much time on your hands.

You want feedback on $1 nightlights?

It sounds like a creepy household!

Which one?

Eureka, California Eureka, Colorado Eureka, Nevada County, California Eureka, Illinois Eureka, Indiana Eureka, Florida Eureka, Kansas Eureka, Louisiana Eureka, Missouri Eureka, Montana Eureka, Nevada Eureka, North Carolina Eureka, South Dakota Eureka, Texas Eureka, Utah Eureka, Polk County, Wisconsin, a town Eureka, Winnebago County, Wisconsin, an unincorporated community Eureka Center, Minnesota, an unincorporated community Eureka Center, Wisconsin, an unincorporated community Eureka County, Nevada Eureka Springs, Arkansas Eureka Township, Adair County, Iowa Eureka Township, Michigan Eureka Township, Dakota County, Minnesota Eureka Township, Valley County, Nebraska Eureka Valley (Inyo County), California Eureka Valley, San Francisco, California, a neighborhood

^^^^^ There we go, a retired engineer with LOTS of time. :^)

For a nightlight? I think I could work that out myself, but what the heck. I bet they are some pretty looking drawings!

[Andy]

Andy comments:

There's other stuff in the blue LED lamp that makes it work only on the half cycle (there's maybe 50%), and a couple current limiting resistors also.... That's why the total power is so high... It is designed with some internal protection against transients that are always active.

Yes, I agree completely that the white versions are preferable from a "light output" standpoint. If they become available, for a buck, I'll buy them instead.... Actually. the next time I'm at TANNER in Dallas, I'll buy a high output white and substitute it and see how it works.... Thanks for the suggestion...

Andy in Eureka, P.E.

[Andy]

**** Betchurass.... LOTS of time... That's why I'm on this newsgroup.....

*** Of course you could. However, my philosophy has been " don't try to re-invent the wheel ".... When I see something that works good, for less than I can build it for in my home workshop, I want to learn about it before starting my own crusade....

I found that there's no way I can do it for a buck, and, whoever made it, did it well..... No reason to get inventive on this.. Been done... works well... sells cheap... available locally....

Nuf Said ??

Andy in Eureka, Texas

PS So did you want a ***.sche file for PSPICE, or not ??

[Andy]

Andy also replies...

Oops, I forgot ..

Eureka, Texas , one of the five Eurekae in Texas

Mine in about 80 miles south of Dallas , in Navarro County, on the banks of Lake Richland-Chambers..... what there is left of it during this drought.....

[Han]

George wrote in news:j556om$vfk$ [e-mail]:

This thing has been in constant use for at least 20 years. LEDs didn't exist,at least not publicly available, when we bought them (another one is still in storage somewhere).