High-efficiency LED Reading Lamp





Introduction: High-efficiency LED Reading Lamp

Have you ever wanted to read at night but are frustrated by wasting energy with those 50 or 60 watt lamp light bulbs. If you are like me, you bought a few dozen CFL's. But when you realized that the light given off by those bulbs is too harsh and unnatural (even the so-called 'Sunlight Simulator' bulbs), you decided they had to go. So you decided to try a clip on LED book light. But like me, you were probably frustrated with the thin, dim glow and having to move it every time you turned a page. For years I put up with this. Until I found a website called Instructables. Instructables gave me the inspiration to build my own LED lamp. Sure, you could buy an LED bulb. But the el-cheapo bulbs flicker and the ones that don't are too expensive (they start at 30 US dollars). I set out to build one for less than 10 dollars. Sadly, thanks to expensive shipping rates (and I live in the U.S. too!), it ended up being a little more. But in the end, it was worth it. The entire array, including all 8 (yes, 8) LEDs and 4 resistors draws a grand total of 1 watt per hour! That's a savings of 59 watts over the incandescent lamps I used to use and 29 watts over the CFL that replaced the incandescent bulb! And the light is bright but not too bright and is easy on the eyes. So, on to how I built it.

Step 1: Materials

From allelectronics.com (www.allelectronics.com)

White Ultra Bright 5mm LEDs x 8 (I went ahead and ordered 100 for other projects around the house since they were so cheap) Category # LED-121

270 ohm, 1/4 watt resistor (I ordered 1,000 to use when I build the LED lights for my house to run off of; no really I ordered that many!) Category # 291-270

From Radioshack

10 packs of 75 foot long rolls of 22 gauge solid core wire (no really, I did buy that much).

On to tools.

Note: you can buy however many LEDs, resistors, and wire you want. I bought so much because it was on sale for really cheap. In the end, I'll save money.

Step 2: Tools, Tools, and More Tools

Actually, you don't need that many tools. All you need is:
1. Needle nose pliers
2. Regular wire pliers
3. Electrical tape (I strongly recommend that you use electrical tape and not duct tape, It's much safer and worth the extra coinage)
And that's all! Next step please.

Step 3: Array Design

I used the LED series/parallel array wizard available at http://led.linear1.org/led.wiz
The source voltage is 12 volts. The diode forward voltage is 3.5 volts. The diode forward current is 20 milliAmperes (mA). The wizard spit out two possible configurations. I used the second configuration (the one with the 4 parallel arrays of 2 LEDs and one resistor each). I chose this array because it meant that I wouldn't have to buy 2 different types of resistors. On to the next step, if your brave enough! (evil laugh)!

Note: sorry, couldn't get a picture of the schematic.

Step 4: The Beginning

The first item on the list is to tie the positive lead of one LED to the negative of another. Twist the two legs together. If you want, mark the positive wire in some way so that you won't lose which one it is. I used 2 LEDs in series, but you can use other configurations if you want, it depends on your tastes and, possibly, budget. My lamp originally used a 100 watt incandescent bulb. It got very hot so the makers drilled eight 5mm holes in the back. I just got lucky. Some of you may have to drill the holes yourself. Just make sure they are 5mm. And be very careful, a friend of mine got hurt drilling a hole in metal. Once you twist the LEDs together, put them in the two holes that are close together. Repeat until you fill up all possible holes or run out of LEDs, whichever comes first. On to the next step.

Note: if you're having trouble keeping the wires together, use the needle nose pliers to make a loop in the wire and crunch it together. It should keep everything together nicely. I was lucky enough not the have to do this, but the needle nose pliers are just in case.

Step 5: Resistors

I strongly recommend you use a resistor. Most people would just use 4 of these LEDs in series, but the resistor is also a current limiter. Without it, the current will run rampant through the LED (LEDs have the amazing ability to draw as much current as you can provide, even if it means their death). The LED will eventually burn out, although not as fast as if you just hooked one up to the power source. The resistor was chosen for me by the array wizard and using it allows me to use the LEDs to their full brightness without shortening their life span. Run 1 resistor to each of the LED arrays. You could run 1 resistor to to 2 arrays or all 4 (or more) of them. But compared side by side, they are not as bright. After you have the resistors, use electrical tape to keep the arrays from shorting out. Next step, if you feel up to the challenge.

Step 6: A Lot of Wiring

Using some scrap wire to wire the resistors together. Do the same with the negative side of the LEDs. Leave only one lead exposed. This is just a simple step. Once you're finished, on to the next step.

Step 7: The Power Source and Its Wiring

I am using a temporary 12 volt 3 amp power source. My lamp just uses the center of the pole to run the wire. I used a coat hanger to pull two new wires through this same location. Every lamp is different. A simple solution would be to tape the wires to the outside. While that would be more noticeable, it works in a pinch and is very easy to set up. I did this step before I thought about writing this Instructable, so I have no pictures of me working on this step, only the final product. Sorry. One final step, and we should be finished, hopefully.

Step 8: The Final Wiring Step

Once you have found a way to run the wiring to the power source, strip the end near the LED and wire the positive to the positive side of the diodes (the part connected to the resistors) and the negative to the negative side of the diodes. Tape it all up and test it out. If everything is working correctly, CONGRATULATIONS! If not, then you will have to go back and recheck all of the wiring. Once every thing is working correctly, tape it all up. Put the wires wherever you want. Just be creative! That's all. Thanks for listening to my rant...uh, I mean Instructions! Happy sailing!

Step 9: Total Cost and Other Possible Edits

Upon review of my Instructable, I realized that I forgot to include the costs. As a weak defense, I wrote this Instructable at 11 pm and my normal bedtime is 9 pm. Anyway, here's the costs.

Ultra-bright white 5mm LED x 10; $.65 each or $6.50 for all ten (I personally recommend buying 100 because the price goes down to $.50 each)

1/4 watt 270 ohm resistor x 10; $.05 each, unfortunately all electronics requires you to buy a minimum of 10 so the price is $.50

Shipping from All Electronics is usually $7.00 for addresses in the 48 contiguous United States.

I believe one pack of wire at radioshack is $10.00.

All totaled, the cost is $24.00

Happy Sailing and please vote for me!


DISCLAIMER! PLEASE READ!: I am in no way responsible for any injuries you may obtain from this project. This includes poking a hole in you finger with the LEDs, burning yourself if you do decide to solder, blinding yourself by looking directly into the LEDs, or any other injuries that might result. Please be careful and follow standard safety procedures. These include being very careful around hot solder and soldering irons, regardless of whether they are on or off. Never look directly into any light source, no matter how dim you think it might be. Always use insulated pliers when working around any voltage source, regardless of how low it might be. And always use common sense when undertaking projects like this. Failure to do so could result in serious injury.



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    21 Discussions


    2 years ago

    Hi. I think I can add your schematic for the interested:

    12V 8-LED Array.png

    Try Parts-express dot com. Their price is so much better than what you quoted. They also include the resistor with the LEDs.

    Nice job, by the way.

    Hello Friends, I want to know information about Industrial LED lamp means street light or more illuminated LED lamp. if any body have this info then please share with me my personal email id is vipulprajapati84@yahoo.com

    1 reply

    First: don't post your email address on a public place like this. Spambots can grab it and flood your inbox. Second: LEDs are used industrially. Im my area, they've switched the traffic lights to LED bulbs. However, they are not quite bright enough for street lights. The LEDs would need to be diffused and diffusing them changes the brightness. Some companies do make LEDs bright enough for street lights, but they are very expensive (>100 dollars per bulb). And they would still need several bulbs to make the light bright enough. To shorten the above, LEDs are not economical yet because of price. But in the future, as the price comes down, they will likely be used because of the energy savings they provide.

    No. I plan on converting my parents house to all LED lighting and when I get my own built, I'll do the same. I couldn't help it. I like to build stuff and eventually all of the resistors will have a home somewhere where they are useful.

    It does need a diffuser. The LEDs reside just behind the original bulb holder so even if you look directly at the lamp, it's not too bright. The first picture in step 8 is about as bright as it gets. The main problem is the uneven light patter it spreads on the wall. Look at the second picture in step 8 and you'll see what I mean.

    you could always find an ac adapter from something small such as a cellphone charger, radio, battery charger (ironic stuff)... just a note.. make sure you take a small lesson on voltage (if newbie) so you don't burn your electronics...

    2 replies

    Oh, and I do plan on using a small 12V 500mA AC adapter for the small stuff like this lamp. A simple 12V 500mA adapter would power 40 or so of the LEDs in my configuration.

    Using resistors is quite a lossy process. Did you consider using some form of regulation and a single, efficient 1w LED at all? I love the way you crammed it all into a standard angle-poise form factor. It's really practical!

    4 replies

    I did but resistors were the cheapest. Each resistor was only $.05 US dollars. Plus the only 1 watt LEDs I could find were 12+ US dollars.

    In the end, it would have cost about the same. Do you know anywhere I might could get some cheap 1 watt LEDs?

    Hi tech101 Thanks for your reply and the info. I've been inspired by this instructable and want to try similar! You can get a bunch of amazing and cheap (free postage worldwide) LED stuff at these sites: www.dealextreme.com www.kaidomain,com Takes about 2 weeks for delivery. You can get 1w LEDs from around $2ish and they also sell constant current sources which operate in various voltages from 3.7.-4.2 DC (for lithium batteries), 12-16 volts DC and even from 120-240 vac. They're really jolly cheap. Both CREE and SSC LEDs are very good, and efficient and quite cheap at those sites. Check out the CREE P7 LEDs which are quad core LEDs, running at 3.7v and 2,8 amps. They're putting out in the region of 500-700 lumens! Anyway - great instructable makes me want to do something similar, thanks!

    Your welcome. The lamp was a lot of fun to make and well worth it. Have you read the last step (I just added another one)? I'll be updating it soon with payback time for the project. I didn't say this above, but the light is concentrated enough that, if you looked directly into the diodes, is just as bright. Lumen-wise, they put out less. Those quad core LEDs sound a bit to bright for a reading lamp. But I do plan on making outdoor spotlights and might use those. But that's a few months off.

    To diffuse, I 'file' the LEDs down a bit. That leaves a nice, rough surface that gives good diffusion. I use like a 220 or higher 'grit' sandpaper, or a emoryboard (nail-file).