How to Make Cheap But Very Powerful LED Bulbs

It's been almost a year since I started to "LEDify" my home, with results more or less encouraging, but only an accident made ​​me find the best solution so far.

Step 1: Motivation

How often happened that you or someone in your family, by mistake, to overthrow the desk lamp? If you are like me, this has happened many times...  For this reason, the last time my offspring slammed my desk lamp one more time, with an innocent "UUPS!", I exclaimed Enough!

Warning! CFL bulbs contains a small quantity of mercury and this is a very toxic substance.
If by accident or intentional, you have broken an CFL bulb, it is advised to ventilate the room as good as possible, in order to dissipate the toxic vapours.

I decided that I have to replace the CFL bulb from the desk lamp, with something more shock resistant...

But that could withstand the treatment of a 10 years child and at the same time to make enough light to work at desk in good condition, to be reliable in operation and decently priced? If only a few years ago, there was no a solution to this question, the answer is now clear: a power LED.

Step 2: Materials

As I already had some Cree MX6 Q5 LEDs with 3W power and maximum light output of 278 lumens used in some older projects, I decided to use them for this project too. The LED will be placed on a 5cm x 5cm heat sink recovered from the chipset of an old computer motherboard.

For simplicity, I decided to use a switching power supply of a mobile phone, perhaps together with an electronic adapter that would give me the necessary voltage and current to power the LED. For this purpose I have chosen the power supply of a defective mobile phone Siemens A52 having, according to the manufacturer, an output voltage of 5V and a current of 420mA.

An socket from am old CFL bulb should protect all the electronics.

Step 3: EVRIKA Moment

According to manufacturer specifications, Cree MX6 Q5 LED can be powered at maximum current of 1A at a voltage of 4.1V, and I expected I'll need a 1 ohm resistor to lower the voltage by about 1V from the 5V (given by the power supply) to the 4.1V accepted by the LED, and that only if the power supply would handle the maximum current of 1A.

In order to check the maximum current supported by the power supply I connected to his terminals various resistors, measuring in each case the voltage and then calculating the current. Here are the obtained values:

Load            Voltage          Current
-NA-                5.8V            0A
8.2 ohm         4.9V            0.6A
5.1 ohm         3.1V            0.6A
3.3 ohm         1.75V          0.53A

EVRIKA!

To my surprise, the power supply seemed to have by construction the current limited to about 0.6A, value he looks like it stand without problems. Testing in the same way other mobile phones switching power supplies, I found that absolutely all of them are limited by construction to a current from 20% to 50% higher than the one specified by the manufacturer, which now I find it makes perfect sense: any manufacturer will design the power supply so that it will not overheat even if the powered device would be damaged, even in short circuit ... and the easiest way to do this is by... current limiting!

I had therefore, a constant current generator limited to 0.6A, very effective (a power adapter cell phone heats up only slightly during operation), powered directly from 230V AC, ready-made by the factory, with very small size. And this is simply GREAT.

Step 4: Construction

For the beginning I made "the autopsy" of the power supply in order to extract the "organs" to be inserted in the body of the new bulb. As most power supplies are assembled by soldering, extracting consists of cutting with a saw blade... So pay attention to bruises for those less skilful...

In order to fit inside the body of the lamp, it was necessary to make some adjustments.

To fix the board inside the bulb, I used sanitary silicone, taking advantage of its resistance at high temperatures. Before closing the bulb, I attached to the cover (I used a screw) the heatsink on which is located the power LED.

Step 5: Results: Desk Lamp

And here's the bulb assembled. The power consumption is just under 2.5 W and the luminous flux is about 190 lumens, perfect for a economical, durable and resistant desk lamp. And all this for up to one hour of work, except of course the time for drying the silicone and heat-conductive adhesive used to fasten LED on the heatsink.

I was so excited about the success and ease of implementation of this project that after a few hours I had finished another LED bulb.

Step 6: Results: Hallway

Thrilled with the result, I continued to replace some of the CFL bulbs in my apartment with LED bulbs constructed in the same way. I will present these in "fast forward"...

For the entrance hall I used two Cree MX6 Q5 LEDs each having maximum power of 3W and maximum light output of 278 lumens, each powered by a power supply from old Samsung mobile phones. Although the current specified by the manufacturer is 0.7A for each power supply, after measurements I found that it is limited to the value of 0.75A.

Everything was assembled with velcro tape, adhesive and plastic spacers from PC motherboards.

Total consumption of the assembly is this time around 6W for a luminous flux of 460 lumens.

Step 7: Results: Bathroom

For bathroom I used an Cree XM-L T6 power LED, powered by using two switching power supplies from LG mobile phones. Each power supply unit can generate according to the manufacturer, a current of 0.9A, but I found the current practically limited to the value of 1A. The two power supplies are connected in parallel for a total current of 2A.

Under these conditions the LED will produce a luminous flux of about 700 lumens for a power consumption of 6W.

Step 8: Results: Kitchen

If for the hallway and bathroom was not essential to ensure a certain minimum illumination, for the kitchen is a different story. I do not want that my wife or someone else to cut a finger while preparing meal and blame me for this, or worse, blame my precious LED bulb...

To make sure that this will not happen, I decided to use for my kitchen, not one, but two power LED Cree XM-L T6 each having maximum power of 9W and maximum luminous flux of 910 lumens, connected in series. For efficient cooling I used a heatsink recovered from a Pentium 3 Slot 1 CPU, which I attached the two LEDs using Arctic Alumina thermal adhesive.

Although Cree XM-L T6 LEDs can handle a maximum current of 3A, the manufacturer recommends for reliability a current of 2 A, for which they produce a luminous flux of about 700 lumens. After testing several power supplies that proved not to be current limited or limited to a current well above the necessary 2A, I managed to find a power supply which, according to the manufacturer, generates 12V at a current of 1.5A. After testing it using power resistors, I found the current limited to the value of 1.8A, quite close to the planned value of 2A. Perfect!

To secure the heat sink and the two LEDs I used two plastic spacers from a PC motherboard and two neodymium magnets recovered from a damaged DVD drive, all glued with superglue and also a velcro tape.

Although I expected this LED bulb to produce 1300 lumens, a light similar to the old 23W CFL bulb it replaces, I had the pleasant surprise to see that in reality the light produced is visible more intense, all for a power consumption of about 12W, almost half compared to the old bulb.

Step 9: Conclusion

The coolest part of this project is that you can use commonly available components, the only expense is for purchasing power LEDs.

In this way, you can get LED bulbs at a cost of half or even quarter compared to the price of an LED bulb purchased from a store.

I hope that in this way many power supplies from mobile phones will be useful again instead reaching the trash can.

This project is extracted from a series of articles published on a DIY web site I own http://www.schematics.ro/ where you are more than welcome.


Thanks for reading :)

Comments

[sanjay117]

In electronics instructable,what is most important is circuit diagram.
Hereafter please keep in mind.
Thanks

[yardleydobon]

This instructable is terribly, terribly unsafe (i.e. death by electrocution)! No name chargers can be very dangerous, and removing one from its case and putting in a light bulb shell makes it even more dangerous. These chargers are often unfused and have terrible creepage. The large screw base and heatsink are large metal parts that could become electrically hot and touched. The openings in the bulb package could let in debris (like a solder ball) and short hot to Vout or ground. See this video to see an analysis of one of these cheap chargers.

[wexler]

no action man stay at home and do not read instructables anymore

[The Freak]

Siemens, Samsung, I see names everywhere. No name you say? Though you are right, some of those dirt cheap brandless chargers are a no go. Nonetheless I see insulation tape or shrink tube on every single picture, I'd say he did a good and safe job. The wall socket part is the hot zone, the secondary is not that much of a big hazard if you ask me.

[terezkaterka]

yardleydobon , I had a lot of phones in my life, and none of my sources died. It is true, however, that many of China's main sources are very dangerous.

[cozysmartlights]

Hi Tudurache, thanks a lot for this tutorial, it is really helpful. But I'm a little bit confused about the voltage required by the LEDs you used in the kitchen. Can you kindly specify on that? Also, I can see you made these bulbs about 6 years ago, are they still working?

Thanks

[DanielZ101]

Salut explica si in romaneste te rog

[NarsinghB]

Hai

[RincewindT]

Great one, thanks!

[MusacC]

se cunoaste ca esti roman.....dupa explicatii

[AhmedI52]

i want to start led bulb business on my own name in india..

can anybody tell me about cheap and powerful led bulbs manufacturers/ supplers in india so that i can start the business.

my contact detail is aiftikhar21@@gmail.com

cell No. 923335255121

[NegiJ]

i want to start led bulb business on my own name in india..

can anybody tell me about cheap and powerful led bulbs manufacturers/ supplers in india so that i can start the business.

my contact detail is [e-mail]

cell No. 710009876

[Mani Kurian]

Where can you get the replacement LED light ?

[tudurache]

Yes, the heat sink is required... without it, the LED will have a very short life span... The heat sink is not required when the power of each LED is very small... let's say 0.25W (like in LED strings)...

[HamedH]

hi

you say about heating problem but i give my another product such this to my friends for long time may be 4 years ago and he was use it in bedroom in room temperature for long time approximate all along nights and he wont told any problem for its performance and yet it work fun and just led chip show a little decrease in brightness that every one cant not be recognized it with his eyes however experts may found it but it work.

[tudurache]

Great! It is sturdier than I thought :)

[tudurache]

Ah... the lamp shape is great, because of the cover it won't hurt your eyes if you look directly to it. However you have in the same closed enclosure, both the LED which produce a lot of heat and the power supply which is affected by the heat (it contains sensitive electronics). If you only use this bulb for short periods of time (in the fridge) it should be ok. Otherwise you might have an overheating problem.

[HamedH]

hi

excuse me tudurache i want you just to say about my lamp bulb shape because i create it with my own idea!

[hamedshh]

hi

how many concession you give me for for my innovation while you see my hand made products for it size and shape in pecent?

[tudurache]

I didn't really understand your question... sorry