Super simple high power LED driver

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 1 Get 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.

Comments

[panchavanparivendhan]

but.......u still did'nt say the value of resistance needed for this project.

[ptacnik]

I Have a 90W LED that works at 21V and consumes 700mA, if i have lots of 3.7 Li-Po 5000 ( 1 Cell ) how many would i need to power this baby, i know i can use a Voltage doubler with capacitors and diodes so Voltage is not my main concern. How can I know the amperage on my custom battery pack ? just by measuring the Resistance and multiplying by voltage ? if this is too high how can i regulate it :(
I'll install a micro piezo blower to cool it down ;-)

[bjcryss]

Can i put the LED with the LM317 on the same heatsink? Won't it shortcut or something ?

[PedroDaGr8]

Both should be electrically isolated from the heatsink (the 317 by a silpad or similar and the LED by the star). That being said, putting both on one heatsink is asking for trouble.

[aleixoar]

Excellent but if power source has highest voltage you can't regulate with a solid resistence, i suggest a LA7812 it's cheaper and will work in a range between 13 and 16v with a good heat sink.

[PedroDaGr8]

I assume you mean LM7812. It isn't much different than the LM317. LM317 has a dropout voltage of around 2.5V and the LM7812 has a dropout voltage of around 2V. That being said, its 6 of one half dozen of the other. Both will dissipate the same amount as heat because dropout voltage only matters when Vout is getting close to Vin-Vdo.

[hamtons]

Hi, I was trying to design a driver with LM1084IT-ADJ.

I noted that the reference voltage is 1.5V, I need 3 Amps so 1.5/3 = 0.5 ohms for the resistor value right?

Then another thing is how do I know what watts the resistor should be?

I'm running 3 LEDs 3.2V each at 3Amp in series, for a total of 9.6V.

Is it 1.5V*3amps = 4.5W or is it 9.6V*3amps for nearly 30W?

Thanks (:

[PedroDaGr8]

the first one. You are measuring the voltage drop across the resistor.

[hamtons]

4.5W it is. ok thanks (:

[PedroDaGr8]

Don't forget to give yourself some headroom on the W. I wouldn't use a 5W resistor. Its going to get quite hot and there just isn't much headroom should things go haywire. 7.5W or 10W resistor would be better.

[TheGreatS]

Ohm never forgot his dying uncles advice.

"Remember: with great power comes great current squared times resistance"

Excellent instructable by the way, bravo.

[PedroDaGr8]

Instead of the LM317, I like to use the Sharp PQ12RD21. It is a four pin voltage regulator, similar in nature to this one but the fourth pin is an on/off pin which can be connected to a PWM for easy dimming. Additionally, because there is a separate pin for PWM dimming, the PWM doesn't need to handle large amounts of current. A simple 555 PWM circuit can do it.

[zami]

Thnx for the gr8 article.It really helps.I have a question.
I m making a 90W Led panel,Using 1W led(rating 350mA,3.2V)
In which design shud i make it??

And for Led lights panel,Constant current source is better or Constant Voltage source??????
n do the series or parallel combinations of LEDs affect the efficency or temperature of the panel....


Please Email me the design at
[e-mail]

[PedroDaGr8]

For high wattage LEDs, ONLY use Constant current. Additionally, series is better if you have the voltage overhead. You will need a constant current driver for every string of LEDs you make. so for example
          |--CCDriver--LED-LED-LED-|
          |--CCDriver--LED-LED-LED-|
12V--|--CCDriver--LED-LED-LED-|--Ground
          |--CCDriver--LED-LED-LED-|
          |--CCDriver--LED-LED-LED-|

[enLighten]

I am looking for a low cost method to adjust the intensity of a single 3W Cree LED using a 12 VDC or 24 VDC input power. It appears that the LM317 design would require an expensive 2 Ohm Rheostat to make the adjustment. I need the light from the LED to be fairly stable (i.e. not fluctuating). Any idea's that can be tested?

[PedroDaGr8]

Use a PWM for dimming. Voltage dimming is spotty at best on LEDs; additionally it tends to be non-linear and causes color shift. Personally, instead of the LM317 I would use the Sharp PQ12RD21. It's a 2A 12V reg like the 317 but it has a fourth pin dedicated to PWM. So you can use a simple 555 based PWM circuit.

[nigel cox]

What input voltage are you using in this circuit please, thank you Doc Cox

[chse720]

i am wanting to power an LED that requires 16.2V and between 1.5-2.5A. I would like to use a current of 2A for this project, how would i go about doing this and power source would you suggest? i would like to use a dewalt rechargeable 18V battery

[ironsmiter]

So, when it comes to circuit design, I can be a bit addlebrained.

What's the advantage(besides power savings) of the modded PWM version ov, say, using a variable resistor in THIS circuit.

To control brightness.

Or am i confusing voltage and amperage yet again?
(sorry, bast my normal bedtime)

[markee2]

Nice instructables. No doubt this is one of the simplest LED driver. Its only limitation is current is limited only up to 1.5A. 
I found a  very cheap LED driver that claims can drive up to 10A current
I dont know know and never tried building it building it, here is the circuit
copied from a site
http://www.simple-electronics.com/2011/09/cheap-power-led-driver-circuit.html

here is the sites circuit

[PabloMDP]

Hi, i have 4 leds 10w (9 - 11v 1amp) and i have a 12v 10amp power supply. Can i make a driver only with one LM1084IT-ADJ? I want to dimmer the leds with one control. Thanks!!!

[Avaruushirvi]

From datasheet ==> "The LM1084 is a series of low dropout voltage positive regulators with a maximum dropout of 1.5V at 5A of load current. It has the same pin-out as National Semiconductor's industry standard LM317."

So you cannot use full bright!

[PabloMDP]

Sorry, i have another question. What happend if i put 4 leds in parallel, 1 amp each led, all with only 1 regulator LM1084IT-ADJ, (0.3 ohm resistor) and 1 led is damaged. In this case, the other leds work at 1.33 amps? Thanks, and sorry for my english.

[Avaruushirvi]

IF that one led shorts, then 4 apms go through it... And If it open then it's go just as you suspected!

[burton2663]

im looking for a 1 watt luxeon led driver to maximize brightness when connected to the outputs of the vu meter lm3915, an actual schem would be nice tnx

[eugenehaller]

 AI, I am amazed that you are still diligently answering comments two years after you you made your instructable.

I am trying to build this, but I am using two 10w LEDs with a Vf of 3.6 and a current consumption of 2800 mA. For the life of me I can't figure out what regulator to use. Any ideas? 

[yugang]

Hi Eugenehaller,

could you help me in designing a circuit for lighting 10 w power LED or 1*10 watt leds..

Thanks,

Yugang

[valveman]

Use an LM338 it is rated to 5A.

[seethasub]

you have to add a PNP power transistor with IC to incease its current rating.

(Transistor 2N6111 On Heat Sink with LM317 ) 

 

 

 

 

 

 

 

 

 

 

 

[Artificial Intelligence]

Hi, sorry for not replying. I must have missed your comment. I have not tried using 10W LEDs with the LM350, but I don't think it's a very good idea, because when I use the LM317 (1500mA max) to drive a LED that just uses 700mA, it gets very hot and needs a pretty big heatsink. This happens because both the LM350 and LM317 are pretty inefficient, so they "burn off" the power as heat. For very high power LEDs, you might be better off with a more efficient regulator. Try the LM1084IT-ADJ. It costs more than the LM350, but it's more efficient and can handle up to 5 Amps. It has the same reference voltage and pinout as the LM350/317, so you can use my instructable with it.

[doransignal]

try using a LM350 it is rated at 3 amps or 3000 ma

Lee

[aekara]

i need help of powering a 30w high power led



 THE LEDhttp://cgi.ebay.com/30W-White-High-Power-2100LM-LED-Light-Lamp-Bulb-A_W0QQitemZ220708010099QQcategoryZ163866QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D10%26pmod%3D220693236934%26ps%3D63%26clkid%3D5621333683761900258

CAN I USE THE LM317 OR I NEED A DIFIRENT VOLTAGE REGULATOR

THE INPUT POWER WILL BE 16V

[yugang]

Hi,

could you please help me in designing to light 10w power led or 1w * 10 led?

I appreciate your help!

Yugang

[macnomad84]

DATA SHEET
http://www.national.com/ds/LM/LM117.pdf

"The LM117 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 1.5A over a
1.2V to 37V output range."

P = V * I = 16 Volts * 1.5 Amp = 40 W

I think you can. Go for it. Someone correct me if I'm wrong. Gonna keep reading this DS...

[ngwanhoe]

I anyone could show me a simple circuit for :-

Input voltage : DC 4.8V - 5.6V
Led : 3 X 3w Leds, working voltage 4v - 5v each led, so had to wire in parellel.
Prefered current : 0.8A - 0.9A

Now I am just using resistor to do the job.

Please email to [e-mail]

Thanks a million.

[Jayvis Vineet Gonsalves]

You can wire the LEDs in Series and for the resistor, you can use a 1.56 ohm resistor if you desire 0.8A of current. Use the schematic given in the instructable.

[ngwanhoe]

Thanks Vinet,

If wire the Leds in series then I would have to put in 8v - 15v power supply. Don't have space for so many batteries.

[pandyaketan]

My projects might provide simple answers to your complex issues...

reg
ketan
--------------------------------------------------------
"May the good belong to all the people in the world.
May the rulers go by the path of justice.
May the best of men and their source always prove to be a blessing.
May all the world rejoice in happiness.
May rain come in time and plentifulness be on Earth.
May this world be free from suffering and the noble ones be free from fears"
---- Vedic blessing

[broxlin]

Hi!
I have 50 blue and 50 white leds, here are the spec:
" http://i1104.photobucket.com/albums/h329/broxlin/Proiect%20Diamant/Blue.jpg " and " http://i1104.photobucket.com/albums/h329/broxlin/Proiect%20Diamant/White.jpg ".
This will be the light for my reef tank.
I want to make 2 or max 4 lamps, if it's possible, so one circuit for 25 / 50 leds.
If I put less leds, the number of sources will be higher and the cost the same.
How can i make it better?
Thanks!

[Jkirk3279]

Hi.

I've been studying this subject.

This regulator seems just what I'm looking for. Not tuned in yet on the "constant current" concept though.

I want to drive twenty 1 watt LED's in series. Each uses 2.79 volts and 350 mA.

So if I drove them in parallel I'd need 2.79v but a staggering 7 amps !

I asked an electronics teacher and he said "run them in series".

So then you need 28 volts but only 350 mA for 20 watts, plus a balancing resistor.

Very little power wasted.

As I understand it each LED sees 350mA, but the voltage pressure drops progressively until finally it hits the resistor.