LED Night light

I want to make a LED night light 120VAC with 3or 4 white LEDs what do I need and how do I wire the circuit?

Thanks

http://home.comcast.net/~theledguy/ and select "LED nightlight" in the left frame.

george.

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georges80 said:
http://home.comcast.net/~theledguy/ and select "LED nightlight" in the left frame.

george.


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Interesting circuit, but IMO performance would be about the same with the elimination of all the resistors and the zener diode and putting the LEDs in series. Efficiencies would go up when resistive losses were eliminated and double again when the LEDs went in series rather than parallel.

Removing half the parts (and cost) seems an advantage to me.

A low value fuse might be in order, however, as would serious insulation.

Doug Owen

I have a couple of his nightlight LED around our house. I wish he made them pre-assembled with a wide angle LED (Darell did that for me) and they work great. Very small, very low power consumption.

Wayne's circuit is fantastically small, and isn't anything that I'd call a power hog! The latest design of the board does have an on-board fuse. They are things of beauty, and you can string about nine LEDs in series on them for some pretty serious light. I run one LED on most of mine, but several have two. And for fun I made an 8-LED unit of all white, and that thing is insanely bright!

Hello there,

Here's my circuit:

http://hometown.aol.com/xaxo/index.html
(scroll down to bottom of page)
The zener is a 9 volt model.

The values have been chosen to provide a full 25ma to
the LED.
The total power useage is the lowest possible, about
a quarter of one watt!
Note the input fuse. This is required to stop
overheating or parts explosion if the cap shorts out.
Caps typically fail short, so i included a fuse.

I have an actual working model that's been running for
something like a year now with no problems.

Here's some of the design equations:
Vin=120vac
Vz=9
v=Vin-Vz/1.414
Z = 1/jwC + R1
i = v/Z


Good luck with your LED circuits,
Al

[ QUOTE ]
MrAl said:
Hello there,

Here's my circuit:

http://hometown.aol.com/xaxo/index.html
(scroll down to bottom of page)
The zener is a 9 volt model.

The values have been chosen to provide a full 25ma to
the LED.
The total power useage is the lowest possible, about
a quarter of one watt!
Note the input fuse. This is required to stop
overheating or parts explosion if the cap shorts out.
Caps typically fail short, so i included a fuse.

I have an actual working model that's been running for
something like a year now with no problems.

Here's some of the design equations:
Vin=120vac
Vz=9
v=Vin-Vz
Z = 1/jwC + R1
i = v/Z


Good luck with your LED circuits,
Al



[/ QUOTE ]

I like your circurt but what kind of zenior diode is it and what rating of fuse should I get? and how many volts for the capisator?

Hello there LEDUser,

It's a 9 or 10v zener (or thereabouts).
The fuse is rated 350ma or close to it;
I used a 500ma fuse.
The cap is rated 400v.

Good luck with your LED circuits,
Al

MrAl's circut is pretty nice I think. He sent me a kit to make it. I assembled it but I need to stuff it in something. I did not know it at the time (When I got the kit from MrAl) but I have since learned that I am good at starting projects and only finishing them half way. Some day I'll stuff the whole assembly in something and hope it lights up.

Part of the problem is I'm not very good at assembling electronics, I can do it but I'm not that refined at it...so it turned out much larger than it needed to /ubbthreads/images/graemlins/icon15.gif

I went to both dat2zip and MrAl's sites but found that both circuits have a Vin of 120VAC. Is there any version of LED night light that operates on 240VAC?

Hello reefphil,

To run at 240vac instead of 120vac all you need to do
is change the value of the cap and go up on the voltage
rating.

The cap value should be half, about 0.3uf.
The voltage rating of the cap should be at least
600v, but i'd use a cap with a 700v or 800v rating.
Everything else should remain the same, including the
9v zener diode unless you use more then one LED in series.

Just to note, the values and ratings of all the parts
were chosen very carefully to minimize power dissipation
and to take into account known failure modes of the
various parts. There is an option to use a lower
value cap (for example 0.2uf instead of 0.3uf) with the
only side effect being less current (and therefore less
brightness) for the LED. All the other parts should
stay the same, unless you plan to use more then one LED,
in which case you can increase the zener voltage by 3.3v
for each added LED (white color). This means to run
two LEDs in series you should use a 12v zener; 3 LEDs
use a 15v zener; 4 LEDs use a 19 or 20v zener.

Just to note, the frequency reaching the LED is twice
the line frequency, so it wont blink noticeably.

The other interesting thing about this circuit is it
will still use only 1/4 of a watt (one quarter of one watt)
while maintaining full brightness, when used with
the recommended parts above at 240vac.


Good luck with your LED circuits,
Al

Hello MrAl,

Thanks for the clear and simple explanations. Even a non electrical trained person like me can understand. Will try out the circuit soon.

Hello again reefphil,

Oh ok great. As i was saying, the 120v model has been fully
tested and has been running for about a year now.

One of the great things about this circuit is it only
consumes about 1/4 of a watt, so nothing gets hot. In
fact, nothing even gets warm!
This means it can easily be put inside a plastic case
of some sort. I used one of those little adjustable
night lights from Home Depot after removing the guts.
The warning with these 'standard' night lights is that
they cant be kept near curtains and other things like that.
With the LED night light, it doesnt matter because it doesnt
get warm.

Good luck with your LED circuits,
Al

For those that don't want to build their own...

Costco has a sixpack of LED nightlights for about $9.99.

It uses an interesting reflector at the top to diffuse the
light from a light blue (almost white) LED.

They use 1/4 watt. A photocell turns them off when the ambient light is high. I found that a 100K resister across the light sensor keeps it off till it's a bit darker.

A picture of the light in use is at http://www.tanj.com/lights/nitelite1.jpg

A look at how the light is reflected is at http://www.tanj.com/lights/nitelitedetail.jpg
and a picture of the relector, diffuser and circuit board
are at http://www.tanj.com/lights/niteliteinside.jpg.

The orange wires in the last one are not part of the design. I added them there to confirm the light sensor's response to various resistors.

In all, I like these little units. No disipated heat and plenty bright enough to avoid stepping on cats in the middle of the night.

Daniel

[ QUOTE ]
gadget_lover said:
Costco has a sixpack of LED nightlights for about $9.99.

It uses an interesting reflector at the top to diffuse the
light from a light blue (almost white) LED.

A picture of the light in use is at http://www.tanj.com/lights/nitelite1.jpg


[/ QUOTE ]

Thats funny - that is the same nightlight that our industrial designer gave me to hack open after they bought them. I have this sitting at my desk at work taken apart. I wonder if i can change my job title to flashaholic yet /ubbthreads/images/graemlins/grin.gif

What's wrong with the traditional neon nightlight?

[ QUOTE ]
What's wrong with the traditional neon nightlight?

[/ QUOTE ] Power consumption? Lamp life? Construction cost? I dunno.

Nightshift: Are you one of them Reverse Engineers? /ubbthreads/images/graemlins/smile.gif

Hello All,

I couldnt help notice them lights at Costcos too,
so i picked up a pack

Of course i had to open one up too, and did a full
analysis of the circuit.

I've found the circuit to be WAYYYYY over complicated,
with wayyyy too many parts for what it does, and not
only that, it tries to do too much as well. Do you
really have to turn an LED night light off during the day?

The basic circuit (not the sensor part) is very similar
to my own circuit on my home page. The main difference
is they use a 1/2w flameproof resistor for the input
resistor instead of a fuse. I like the fuse better,
but the flameproof probably isnt too bad either.
The input cap is 0.56uf.

Since they added the CdS sensor they had to provide a
circuit to go with it, which takes two transistors and
some other minor parts. Not only is the circuit overly
complex, a slight change in design would have allowed them
to use a cheaper transistor and also eliminate the 56uf
electrolytic cap they used for filtering the signal
used to turn on/off with the sensor (note the cap ISNT
used to filter the line frequency to provide a more
constant light output! amazing as this sounds).


Ok, now for the good points...

The price is ever so cheap! Six for $10.00 USD.
This probably wasnt the original retail cost i bet.
They put out a nice white light, not tinted.
The case is one of the best i've ever seen. Heavy
1/8 inch plastic with a heavy clear plastic diffuser.
You cant ask for more then this. I bet you could stomp
on it with your foot and not crush the body where the
electronics is located! The price is worth getting
the case alone if you wanted to build your own.

Since the price is so good it doesnt matter about the
complex circuit, but i wonder if this product will
always be found for this price?

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paulr said:
What's wrong with the traditional neon nightlight?

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Now you are being way too practical. For driving from AC power, a neon is hard to beat. Just one resistor.

Hello eliminator & paulr,

I used to like neon night lights myself, until LED's
came along

The only problem i find with neons is that they tend to
burn out or something. When they get older, they
start to blink on and off strangely.

They also dont throw much light at all.
What light they do throw is an orangie color too, which
isnt as nice as the pure white light from the LED's.

Match, anyone?

Take care,
Al