12V LED Accent Floor Lamp.




Introduction: 12V LED Accent Floor Lamp.

Let's convert a dangerous halogen floor lamp into a safer 12V LED accent lamp that can be run from a battery charged by solar cells, or however you want to run it. That should make it environmentally green, less power consumed, recycled material and can be powered by a solar / wind charged battery.

You can even take this camping and run it from the car battery. Really shock people to see someone in a dinner jacket reading a book by the light a floor lamp in the middle of the woods.

Someone coerced me into making this instructable, Well actually they've threatened me after the last two times I made conversions like this, without documenting it. And already another friend is asking me to convert his desk lamp to LEDs. My friends kept after me to take pictures and document the conversions for a web page.

So since I have another lamp, and a digital camera handy, I will try to document as much as I can for you.

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Step 1: Getting a Floor Lamp

Step One:

First go out and buy yourself one of those trendy expensive halogen floor lamps...

Hold on there, that's not right. Give me a minute while I go gargle with Ivory soap...

OK, first start watching on trash days for something interesting. Doesn't have to be a floor lamp, the basic instructions here will work just as well with a desk lamp or even a metal mint case (if you want a really small light).

On our last trash day Here I found a nice brass floor lamp with a movable arm so I could use it over my desk with out taking up desk space, that is needed for all my other clutter. Or I could use it behind my chair as I read a nice relaxing book.

But that halogen 100 watt bulb has to go. I've heard them called a dorm torch. If this falls over when it's on, it can easily set loose paper or carpeting on fire.

So let's get right on with the build, with the next step...

Step 2: Gutting the Lamp

Grab any tools you will need, a screwdriver or two (philips, slotted, or OJ with Vodka), adjustable wrench, coffee, soldering iron, hammer, drill, grinder, files... well you get the point. Take everything apart carefully at this stage, you might want to keep some parts like I did here, to put the lamp back together. The aluminum reflector I'm going to use again to mount the LED insert on to.

Step 3: THE PLAN!

Every good construct requires a good plan. So here I'll discuss The Plan.

I'm using 12V for my power source, it's easy to find world wide, and as such it's easy to find things to customize to it.

I'm using 3 LEDs in series for each segment, saves on resistors. And a quick word on these resistors, if you don't use them, you will burn out the LEDs.

There are two switches in this project, you may only want to use one, but I'm gonna use two different LEDs, narrow beam high intensity LEDs in the center for a spot light effect, and a ring of lower intensity LEDs for a soft glow.

The soft glowing LEDs only use 10mA of current, while the narrow beam are brighter and draw 20mA. So I had to figure out the needed balancing resistors. I found on line, and so could you by looking for "LED Serial Calculator", a calc that would tell me what resistor to use for three LEDs in series.

To make it simple, if you are using similar LEDs, here are the required values:

120 Ohm for 3 X 20mA LEDs that have a forward voltage of 3.3V
220 Ohm for 3 X 10mA LEDs that have a forward voltage of 3.3V

I'm using 5mm LEDs, and they are round with a ridge that has one side flattened. The lead on that side of the LED is ground, or if you are using new LEDs, the longer lead is positive. With that in mind let's get on with the next step.

Step 4: Making the LED Faceplate

Here we are going to start positioning your LEDs into a plastic insert for your lamp.

But first a word about the plastic you want to use.

Having a ready supply of sheet plastic is good to have on hand. Personally I find vinyl siding easy to use. It's easy to shape with a pair of scissors, easy to drill holes into, and can be glue gunned into almost anything.

If you know of a construction site that is doing siding, maybe you can get some scrap ends that would normally just be chucked out. But for those of us who live in a more built up area and don't see the construction till after its finished I have a word of advice. Next time you you go shopping at your local hardware store, checkout the colour samples they give out for siding. 'Nuff said, I have a small pile that I was taking home to the wife for her approval.

In this project I'm using two samples with the same colour vinyl back. Normally I'd just use one and shape the corners to fit inside of the lamp's cone, but here I have a ring that can be re-inserted once the vinyl is glued in from the back.

As you can see in the pictures, I drew a couple boxes on the vinyl for where I want to put the LEDs, and I cut the scrap reflector part of the aluminum insert. You don't have to use square boxes, you could make a star pattern, circles, spirals, or even random positioning. But try to remember the more complex you make your pattern, the more difficult it will be to wire up the right LEDs in the right polarity.

I drilled holes for all 36 LEDs, an inside square of 4 segments of 3 LEDs that will be the narrow bright beam. Around the outside square I have 24 LEDs, six per side, or two segments of 3 LEDs per side.

To drill the holes I should have used a 5mm drill bit, but I don't have a metric drill set, so I used a 7/32" bit which is very close. Just a touch loose, so I glue gunned the LEDs into the holes.

Starting from the center I positioned the LEDs so that all the positive leads are facing the same way. I also soldered the required resistor on the positive side of each LED segment. Once the 4 segments were done on the inside, I soldered the ends together so I had just one point to put wires for both positive and negative wires.

On the outside square of LEDs I wanted to make it easier to identify the wires, so I made each corner positive, and the middle of each side the ground points.

Once all the wires are connected, you should only have three wires to connect to the lamp. Unless you are using one switch, then you only need 2 wires. My lamp will have two switches, so I need two positive leads but only one ground. As following The Plan, all segments come together for a single ground lead.

As you can see from the pictures, I cut out the reflector part of the aluminum ring. This has to be done carefully as this was a very soft aluminum, but I went over it with a file till smooth, then hammered it gently flat again.

The vinyl with all the LEDs and wires can now be glue gunned into place, going over the whole outside edge for strength.

You might be wondering about glue gunning everything to a light source. Don't worry, these LEDs don't generate the kind of heat that the original halogen bulb did. Or for that matter, they won't generate enough heat to melt the hot melt glue.

Step 5: Putting LED Panel Into the Lamp

Now that we have the lamp head made with all the wires needed, we can add it to the lamp body itself.

Here I have to apologize I didn't take any pictures of mounting the switches to the lamp body. I'll leave it to your imagination to drill / file / or however you want to make, or enlarge, the holes in the lamp. Just don't use C4 to enlarge the holes, it will leave the edges too ragged.

Here I'm using a special three connector switch that is supposed to light up the duck billed plastic switch on the outside when the switch is turned on. As such there is a third connector for ground. On a normal switch you don't connect ground to the switch.

If you are using a normal switch then just follow the plan in step three for wiring.

At this point I should mention something important. Safety and testing.

During this construction I have been soldering as I went along, and only managed to burn myself twice. In using a regular soldering iron I picked it up by mistake as you would a pen or pencil. And in this step you can see a lighter, it's actually a micro butane torch that I do soldering on wires away from the normal soldering iron. Well that and I use it when I have to solder a large area that the small iron takes forever to heat up. It takes a number of seconds for a large area of metal to cool down once heated to the point of melting solder. I forgot and went to move the wire out of the way so I could do the next.

Also in the line of safety, once all the wiring is done, I put the aluminum ring back onto the lamp body. But before I did that, I taped off any protruding metal wire ends that could ground out against the LEDs. I mean the wires that go to the switch in this case, I wasn't sure if the switches would have enough clearance not to be pressing against the backs of the LEDs.

For those modifying a normal desk lamp with a kind of funnel head, you can just glue gun the vinyl inside making sure to center the vinyl so the LEDs shine straight out of the lamp.

Anyone looking at the photos will notice that I haven't done something yet, attached a 12V power accessory adapter to the end of the wires yet. You will however notice that I have a red tag on one of the wires. That's so I'll know which wire is to be the positive. Through out the build something I did, but didn't document was the constant testing I'd been doing. Checking individual segments with 12V on a couple of alligator clips to make sure I don't have any bad LEDs, or even worse, if I wired one in backwards. With testing I could make changes before the next step. The red tag I put on once I tested the wiring to determine which wire was the positive wire inside the lamp head.

So next, I add the power adapter end, but wait look at that...

Step 6: Midnight...

It's midnight so I'm taking a hot chocolate break...

Step 7: Finishing Up.

Once the plug has been soldered on, and shrink wrapped for protection, I'm done except for micro adjustments, and taking pictures.

I have this nice portable battery that I can plug into my 12V devices. Here I have finished testing the lamp, taken pictures. Now time to think about additions.

There is a number of instructables out there that deal with steampunk, and as this is a brass lamp, it could take some mods, some wood accents, and black painted designs to qualify it as steampunk.

I could add a carved wooden crest to the front of the lamp, maybe add a meter to make it look better, skin the meter in wood. Ow that idea hurt, I could have used a sheet of thin plywood instead of the vinyl. Damn, Damn, Damn.

Final note, before someone asks, I did meter the lamp out and determined that it draws 0.3A at 12V that is 3.4 watts. YES! I replaced the 100 watt fire starter with a 3.4 watt LED lamp. That's gonna save on power. Even more if like me, you use solar cells to charge up a deep cycle battery to run lights like this.

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    8 Discussions


    10 years ago on Step 3

    On your resistor values.. say for the 20mA LEDs.. I assume the LEDs are effectively 0 Ohms, right? Then don't 4 120 Ohm resistors in parallel give you 30 Ohm, and 400 mA from a 12v supply? I'm a Chem E., but that's what I remember..unless the LEDs aren't 0 Ohm, it's too much current....?


    Reply 10 years ago on Step 3

    Hi There, There is a slight resistance in LEDs, but we don't have to worry about it's internal resistance so much as we do with supplying the correct milli amps to the LED. Too much current and the LED blows.

    I think I see the problem you've made a basic error in looking at my plans. The plans aren't using four parallel resistors to supply one LED. There are four parallel circuits supplying three LEDs each.

    Essentially each circuit of three LEDs is equivalent to a single 9.9V LED that needs 20mA. So the resistor added in series also must be 20mA at the voltage needed to bring the circuit up to 12V. In this case 2.1V . Divide 2.1V with 20mA and you get your resistance value of 105Ohms. The next common resistance value is 120Ohms, cheaper than getting pots for every circuit or trying to special order 105ohm resistors. And if you do the math yourself, don't be fooled when you see 0.105 We are working with mA, so there is a three decimal place shift.

    The math can be hard to figure out without having charts on hand, so I cheat and look up LED Series Calc on Google to find places like http://led.linear1.org/led.wiz that can give me the schematic and values to the LED array I need.


    Reply 10 years ago on Step 3

    Great! Thanks. That's a better way of thinking about it. I guess that means that the LEDs can't be considered 0 Ohm devices, as I thought, then? With regard to the supply, can you just leave it as the AC output of a stepdown transformer, and have the LED emit only on a 50% duty cycle, or would you recommend diode rectification? If yes, how would this change the resistor values?


    Reply 10 years ago on Step 3

    Ouch, this opens a whole new can of worms. Very similar to what is done with XMas tree string LEDs. They have about thirty-five LEDs in series with no resistor. But if you watch them, they tend to flicker, if you want to see it, wobble the string while watching it in a dark room. I suppose that if you had a high speed camera you would also see that they are only on about a quarter of the time, not a 50% duty cycle. After all it's only at the far end of the sine wave that it turns on when it hits max voltages. Myself, I'd add a bridge rectifier, and a capacitor to smooth out the waveform for a nice steady DC. Once that is done, whatever stepdown you've used, you can then measure to determine your final voltage. One word of advice though, those stepdown transformers or "bricks" that get left plugged into the AC mains constantly draw power even when the device is turned off. I started doing 12V LED's because I worked out that a 20 watt florescent tube drew enough over a 24 hour period equal to 480A/H, almost half a killowatt hour of power. And here where I live that meant a nickle a day of wasted power, and we had three of these used as nightlights in the basement. And when I got down to it, my bedside clock was drawing 8 watts of power, with or without the radio on. So now I'm working on transferring as much as I can to a 12V solar rechargeable battery system. Do a walk through of your house and see how many of these sneak thief's there are, chargers for your cell phone, MP3 players, portable drill chargers. It all adds up rather quickly... Hmm, bit of a rant going there. What I meant to suggest is to put the switch between the AC and the transformer, it'll save you some power (and cash) in the long run.


    10 years ago on Introduction

    That looks like a very nice lamp; even before your mod. I love LED mods like this. I must admit; I've got some pretty nice stuff on trash day in my neighborhood. I even sold a dressor for eighty bucks once that someone was throwing away.


    10 years ago on Introduction

    Great idea! Good instructions! I have a halogen floor lamp that has stopped working. I didn't want to buy a new one, or try to have it repaired. I wasn't pleased with the heat that lamp threw out, anyway, so this will be a great way to re-purpose it.


    Reply 10 years ago on Introduction

    Thank you, it was fun to make, and a conversation piece that leads me to discuss solar power and the environment with visitors.