How to make cheap but very powerful LED bulbs

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!

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 heat sink 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.

LED TORCH from discarded mobile BATTERY

INTRO

Here I have used a discarded Li-Ion Battery which is no more working in a mobile handset.
This Battery may not work in a mobile set but it has got a lot of juce left in it to run a small poket size rechargeable TORCH with 5 LED's. It gives a very bright light and does not need a recharge for quite a long time.

Step 1

List of Parts.

1.- One PVC flat Box of size 2 x 3 x 1/2 Inches.
2.- One Single pole single throw switch.
3.- Five Very bright White LED's of 5mm size.
4.- One Discarded 3.6v Li-Ion Battery. (Lithium Battery)

Step 2

In this step follow the Circuit diagram and assemble the parts.
The 5 LED's are fixed to the PVC Box.
The Switch is fixed to the Cover of the Box.

All the 5 LED's are connected in parellel with a switch to the Battery.
LED's are connected PARALLEL because the output voltage of the
battery is 3.6 volts and the White LED runs on 3.3vots.

The longer leg of the LED is the positive pole and the shorter leg is the Negitive pole.
The positive pole should be connected through the SPST Switch, to the (+) side of the Battery.
The Negitive pole can be directly connected to the (-) side of the Battery.

Put some foam pieces around the Battery to keep it steady inside the box from any movement.
Put on the COVER and all is done....
Happy Lighting.

Step 3

 There is nothing special in this step but to see the Photograph and follow the the circuit.


NOTE
To recharge the battery put it in your Mobile Handset and CHARGE.
OR
Buy a Lithium Battery Charger which charges many types of lithium batteries.

How to Charge a Li-Ion Battery.

 How to Charge a Li-Ion Battery Most dedicated Li-Ion-charge integrated circuits (ICs) are designed to charge the battery in this manner. The charging of a Li-Ion battery consists of three phases: pre-charge; fast-charge constant current (CC); and constant voltage (CV) termination. In the pre-charge phase, the battery is charged at a low-rate (typical of 1/10 the fast charge rate) when the battery cell voltage is below 3.0 V. This provides recovery of the passivating layer which might be dissolved after prolonged storage in deep discharge state. It also prevents overheating at 1C charge when partial copper decomposition appears on anode-shorted cells on over-discharge. When the battery cell voltage reaches 3.0 V, the charger enters to the CC phase. Fast-charge current should be limited to 1C rate (0.7°C rate) to prevent overheating and resulting accelerated degradation. However, cells designed for high power capability can allow higher charge rates. Rates should be selected so that the battery temperature does not exceed 50°C at the end of charge. The battery is charged at the fast-charge rate until the battery reaches a voltage regulation limit (typical of 4.2 V/cell, but 4.1 V for coke-based anodes Li-Ion battery). The charger starts to regulate the battery voltage and enters CV phase while the charge current exponentially drops to a defined termination level. However, the output voltage regulation accuracy is critical to maximizing battery capacity and improving its service life. Less battery voltage regulation accuracy means to undercharge the battery, which results in a large decrease in battery capacity. The battery loses about eight percent capacity if it is undercharged by one percent voltage. On the other hand, less battery voltage regulation accuracy also means the battery is overcharged, which reduces the battery service life-cycle. To safely charge the Li-Ion battery, it only allows initiating to charge the battery when the ambient temperature is between 0°C to 45°C. Charging the battery at lower temperatures promotes formation of metallic Lithium, which increases the battery impedance and causes cell degradation. On the other hand, charging the battery at higher temperatures causes accelerated degradation because of promoting Li-electrolyte reaction. This presents a market need for more accurate, efficient and safe battery charge for portable devices. By Jinrong Qian, Senior Member of Technical Staff, Texas Instruments

 

Super simple high power LED driver

Super simple high power LED driver (LM317)

 

 

 

This Instructable will show you how to built a Constant Current for high power LEDs, using only two components.

High power LEDs are getting cheaper and cheaper, however the constant current drivers, to drive them are pretty expensive.

Here, I'll show you how to built a simple and cheap, yet very effective constant current source.

The image shows the constant current driver hooked up to a 1W white Luxeon LED.

EDIT: This LED driver supports PWM, which means that you can control the brightness of the LED(s). Those fancy and expensive drivers doesn't support that. I'll post some schematics and applications as soon as i have time.

Step 1Get the Parts.

 

Here is a list of the the things you'll need.

a LM317 Regulator.
a Resistor (see next step).
a Heatsink for the LM317 (you don't need one as big as mine, I just took one i had laying around).
some Luxeon, or other brands of high power LEDs (see next step too).
some Wire to hook it up.
it will be a good idea to use a heatsink for the LED as well.

Step 2 How it works

The LM317 regulator gives out a constant voltage of 1,25 volts between ADJ and Vout, so by adding a resistor between these two outputs, you'll get a constant current.

Ohm's law says that U/I=R, which means that Voltage divided by Ampere makes resistance.

so if you want to connect one or more luxeon 1W LEDs, which has a power consumption of 350mA, the calculation should look like this: 1,25 (the constant reference voltage of the LM317) divided by 0,350 (the LEDs power consumption) makes 3,57. So if the resistor is 3,57, constant current will be 350mA. The closest E12 value is 3,9 ohms, it will give you a constant current of 321mA. However you can't see any difference in the light output.

If you use 3W LEDs, which has a current consumption of 700mA, the calculation should be: 1,25 divided by 0,7 makes 1,78. The closest E12 value is 1,8 ohms, the output will be 694mA

the resistor must be at least 1W in both calculations.

Although the LM317 is rated for 1,5 Ampere, I wouldn't recommend it for applications that need more than 1 Amperes, because it gets very, VERY hot. the LM350 is equal to the LM317, but it's rated for 3 Amps.

Step 3Assemble it

 

 

 

I couldn't get my schematic drawing program to work, so here is a hand drawn.

The constant current source has a drop voltage of 3 V, so the supply voltage should always be 3 V higher than the LED voltage and can be up to 37V which is the maximum input voltage of the LM317.

Example: You are going to connect two white Luxeon LEDs with 3,42 forward voltage each (mostly mentioned as Vf in common datasheets). The input voltage can change from 9,84V (3,42 + 3,42 + 3) till 37V (3,42 + 3,42 + 30,6).

You can connect up to ten high power LEDs to this circuit.

The higher voltage you supply the LM317 with, the hotter it gets. so it wont be a good idea to supply it with unnecessary high voltage.

Choosing The Resistor To Use With LED

Choosing The Resistor To Use With LEDs

This question gets asked every day in Answers and the Forums: What resistor do I use with my LEDs? So I've put together several different ways to figure it out.

Lets get right to it:
Each of the steps do the same thing. Step 1 is the simplest and we go downhill from there.

No mater what way you choose you must first know these three things:

• Supply voltage This is how much power you're putting into the circuit. Batteries and wall warts will have the output voltage printed on them somewhere. If you're using multiple batteries^*, add the voltage together.
• LED Voltage Sometimes "Forward Voltage" but usually just abbreviated "V".
• LED Current Sometimes "Forward Current". This is listed in milliamps or "mA".

Both of these last two can be found on the packaging for your LEDs or on your supplier's web site. If they list a range ("20-30mA") pick a value in the middle (25 in this case). Here are some typical values, but use your own values to be sure you don't burn out your LEDs!:

Red LED: 2V 15mA
Green LED: 2.1V 20mA
Blue LED: 3.2V 25mA
While LED: 3.2V 25mA

Okay, lets get started!

^* Batteries in series.

Step 1The Web Way

 

The easiest way is to use one of the online calculators provided below.

Just click on one and enter the info from the previous step and you're set! You only need to go to one.

The LED Center (For single LEDs)

The LED Center (For arrays of LEDs)

LED Calculator.net (For single or arrays of LEDs)

LED Calculator.com (For single or arrays of LEDs)

Step 2The Retro Way

 

Go to Evil Mad Scientist Labs web page at this link and print and make your own slide rule-like calculator.

PDF, assembly and usage instructions are all on the page linked above.

It's pretty nifty and ends up being about business card size so you can keep one in that box with the rest of your LEDs.

Step 3The Hard Way (Math!)

All the calculators in step 2 are just doing some simple math that you can do at home:

The formula to calculate resistance in a circuit is: R=V/I or, more relevant to what we're doing:

(Source Volts - LED Volts) / (Current / 1000) = Resistance^*

So if we have a 12v battery powering a 3.5V 25mA LED our formula becomes:

(12 - 3.5) / (25 / 1000) = 340ohms.

But wait! (you might say) When I use one of the other calculators I get 390 ohms! And indeed you do. That's because its hard to buy a 340 ohm resistor and easy to buy a 390 ohm one. Just use the nearest one you can easily find.

To learn more about this magic formula read about Ohms Law.

^* We're dividing the current by 1000 because our listing in in miliaps, or 1/1000^th of an amp.