Author Topic: LED Lighting - 120/220 volts AC and 12/24 volts DC  (Read 12140 times)

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Offline WooferHound

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LED Lighting - 120/220 volts AC and 12/24 volts DC
« on: January 31, 2012, 05:27:32 pm »
-- 120/220 volts AC --

I have always had Nightlights in my 2 bathrooms since they don't have windows. I've been using the standard Christmas Light style of Nightlight until last month. I was changing the burned out Christmas lights about 3 times a year, and they are fairly expensive so I decided to go to LEDs. I looked at several ways of powering the LEDs straight off the 120vac line and didn't really like the methods very much and decided to make the nightlights out of Wallwart transformers. I have a huge box full of these, a wide variety.

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I'm using 2 tricks with the LEDs, flatten or cut the tops off so they throw a wider beam, then use White & Red LEDs together to improve the light color. I like twice as many White as Red and love the pleasant color output. There are red LEDs in the picture but the whites overpower them.

I tried to select small sized wallwarts for use as a nightlight, and 12vdc power supplies so I could string several LEDs together. I then measured the actual voltage that it put out since wallwart voltages vary wildly from their labeled ratings. I then went to this LED Array Wizard page and calculated my dropping resister sizes.

http://led.linear1.org/led.wiz

- Don't overpower your LEDs on a nightlight or they won't last a long time. -

It was a little difficult to tack all the small bits together with a soldering iron. I soldered 3 or 4 LEDs into a string with a 1/4watt dropping resister. Using 3 to 5 LED strings on each nightlight. I cut the wire cumming out of the wallwart to about 1.5 inches and stripped the wires down to within a 1/4 inch of the strain relief then Tinned each wire thoroughly. The wires can then be bent into a "U" shape that you can solder the premade LED strings between. I got some black paint and painted any exposed wiring so you can't see it against the black plastic housing. The LED array can be bent around a little bit so you can aim them in most any direction.

If anyone messes around with a Wallwart be careful not to short the output wires, there can often be an internal fuse that once blown, it is almost impossible to change.

I used my Kill-a-Watt meter and measured my Christmas lights at 4 watts. The LED nightlights showed 1 watt. The unloaded wallwarts measured Zero watt. The best looking one is 12 white and 6 red. Plus the best part, I never need to change the bulb anymore.

You can scale this up to much larger lighting than a small nightlight. The wallwart should be able to power hundreds of LEDs.


-- 12/24 volts DC --

 I have been working on more lighting to use with my 12vdc system. up until now I have been using the 12v lights that came with my 2 sets of Harbor Freight solar panels. They lasted more than a year used almost every night. The tubes started turning black, but I think they quit because of a burned up resistor on the circuit board.


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 In the beginning I started replacing the HF lights with the 12 volt DC lights that you can get at WalMart-HomeDepot-Lowes for about $10. These lights can be found near the area with the fluorescent replacement bulbs and come in 6v and 12v versions. They run on batteries, the package says that it has a jack for external power but I couldn't find one. So I hacksawed an opening in the bottom of the fixture and soldered wires directly to the battery terminals. They put out about the same color and brightness as a HF bulb plus you can replace the bulb with a warmer color for about $7.


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 The old burned out HF bulbs were not really repairable but I realized that they make a perfect fixture to build LED lights out of. I also realized that I had all the parts onhand to build 2 of them rightaway. They are made with white 3v LEDs in strings of 3 with a 1 ohm leveling resister on each string. I am also using red LEDs in these lights to keep the light from looking too blue, these strings are 4 red 2v LEDs with a 2 ohm leveling resister. All the strings are paralleled and fed through an LM317t being used as a current regulator as described in this link...

http://www.reuk.co.uk/Using-The-LM317T-With-LED-Lighting.htm


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 The first LED light I made is 9 strings of white and 2 strings of red LEDs. This makes 27 white and 8 red. I have the Current regulator set to 220 milliamps cause, 11 LED strings times 20 milliamps equals 220ma. All the white LEDs are mounted on perfboard with hole-spacing perfect for an LED. The red LEDs have the clear round caps cut off to make them a wider beam and they are taped with red tape to the exterior if the fixture. This light works great and the LM317t with small heatsink was hardly getting warm to the touch. I tried to bend the LEDs outward on the perfboard to help to spread out the light but I had mounted the LEDs to close and I wasn't very successful.


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 After experimenting on the first light I made the second light with as many LEDs that would fit. It is 13 strings of white and 2 strings of red LEDs. This makes 39 white and 8 red. The current regulator is set to 300 milliamps since, 15 LED strings times 20 milliamps equals 300ma. The red LEDs are mounted on the perfboard along with the white ones. This light works a bit hotter though. With the higher current, the LM317t with small heatsink was running rather warm, almost hot to the touch. I was careful not to mount the LEDs down so close this time and was able to bend the LEDs outward so the light would cover a wider area.


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 The clear covers for the HF lights have some diffusion built into them but not enough at the bottom to spread out the beams coming from the LEDs. I cut out some circles from some clear perforated Freezer Bags and put them into the bottom of the covers and it smoothed out the beams really well. I also drilled some holes in the clear covers to help them get some air for cooling. Here is a picture of my computer area lit up by my LED lights. There is a light from a scanner that is out-of-sight at the top of the computer desk under the lip. You can see what nice color I get with some red LEDs in the mix.


 These lights were easy to make but tedious and time consuming. The bigger light has 47 LEDs and 15 resisters, each with 2 leads, so there are over 100 solder connections on he backside of that perfboard. It took about 5 hours to build each light. I am very happy with the results, they will start at 11.8 volts and should be able to work all the way up to 40 volts. The addition of the red LEDs really improves the quality of the color and it's not a harsh blue anymore. one of them runs at about 3 watts and the other one runs at 4 watts.


W o o f -={(
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Offline ghurd

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Re: LED Lighting - 120/220 volts AC and 12 volts DC
« Reply #1 on: January 31, 2012, 07:12:38 pm »
Very nice.

I often wondered if covering the white painted inside of lamp with AL tape would help if there was red LEDs in the mix.
Cheap to try.
G-

Offline RichHagen

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Re: LED Lighting - 120/220 volts AC and 12 volts DC
« Reply #2 on: January 31, 2012, 08:35:24 pm »
Hi Woof,

I was going to suggest trying out a switching power supplies instead of transformer based power adapters for the night lights as many pull almost no power when off when compared to wall warts, but if you are measuring zero Watts, that is kind of hard to beat anyway. 

Ghurd, Depending upon the white, white coverings are often much more reflective across a wider region of the spectrum than a mirror finish or silver color, although actual silver coated mirrors are pretty good, but most now days are coated with aluminum with reflects only about 90% of incident light in the visible region.  Titanium Oxide is one of the most reflective pigments and will beat out most mirror finishes for reflecting a larger percentage of the light, many paints are well in the nineties for percent of reflected light in the visible sprectum.  The light is diffused however, not focused once reflected from these white surfaces.  For red light specifically, a gold coated mirror is about the best (think of the Webb Telescopes gold coated berylium reflector for the infrared spectrum) as I think it reflects about 99% of red light in that region, although not so well towards the bluer end of the spectrum, which is why it appears, well, gold. 
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Offline WooferHound

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Re: LED Lighting - 120/220 volts AC and 12/24 volts DC
« Reply #3 on: January 31, 2012, 09:38:02 pm »
The LEDs in that lamp are really directional and not much light is hitting the bell of the reflector. They are so directional that I had to put wadded up baggies in there to get the light to spread out enough to be useful.
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Offline jlt

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Re: LED Lighting - 120/220 volts AC and 12/24 volts DC
« Reply #4 on: March 03, 2012, 04:03:28 pm »
 
  Thanks for the tip.

    I used a 9 led  flash light from harbor ft. It had a bad switch.A wall wort From an old cell phone

    I added a couple of resistors in the circuit so it pulls about 129ma . A bit less than the battery's
put out.
     
       It made a good nite light.     jlt