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

[source LED]

It is a great article! We are a US based company in China, Jiangsu Allray inc. I am specialized in 1W high power LED. Any questions on 1W LED, please ask me, I will reply you all the time. :)
Chips of LED are from bridgelux and epistar. Luminous is 130lm/w(avg.), forward current 350mA, voltage 3.0-3.3V, the price with Star MCPCB is $0.4/pcs.
My email: [e-mail], call me Richard.

[gizmo13]

I tried to use this for a 3w led and the only thing that happened was the regulator
got hot.
I first tried to hook it up to 2 3w led's in series then I removed one of them.
Neither time did any of them light up.
I think I need a different regulator. Which one should I use?????
Great aritcle in any case!!!!!!!!!!

[gizmo13]

Forgot to mention the specs of the led's.
forward voltage: 2.9v-3.3v
forward current: 750 mA
hope that helps.

[petebarchetta]

I'm building a bike light version of this running 3 Cree MC-E LEDs, I'm curious if this circuit would run them, also would it interface with a pwm 555 chip if so what would the correct component values be?

[santmich]

another question excuse me for using that resistor 1W LED

[santmich]

hello I congratulate you for what you share only one question in your experience that other component or components you can include it stays cool for both thanks

[arashagha]

hi, if i wanna use 3, 1W leds in series and waNNA connect them to 12-14 volts in my car, what would be the correct R with what Watt??

thx for article

[tdool]

Have a few questions on setting this up for my reff tank and possibly simple Dimming ability

OK I want to do a string of 9x 3w LEDs with fv of 3.6v and run them at 700ma.

So if I am understanding I would run them in series add a Power Supply that delivers 35.5volts { (9x3.6)+3 for LM317 }

For R1 I would use a 1.8ohm resister that can take 1amp. is that correct or do I need 5-10amp?

Now if I want to dim it without any fancy PWM circuit can I just add a Pot after R1 to increase resistance which will lower the current in effect dimming the LED's. will this work?? if so what size Pot will I need?

Thanks

[tdool]

I meant 1w or 5-10w resistor not amp sorry

[svb93]

hi
i have mobile battery (3.7 volt , 900ma)
Can I plug my battery directly to the 1 watt or 3 watt power led ?
please help me
thanks

[spanda5]

http://sevenpanda.com/100w-warm-white-high-power-led-light-lamp-100-watt-p-1415.html#.UFq6bFFfb9Y

[spanda5]

I don't know much about of electronics, But I want to recommend you guys some low price LEDs.
http://sevenpanda.com/100w-warm-white-high-power-led-light-lamp-100-watt-p-1415.html#.UFq6bFFfb9Y

http://toyswill.com

[vallka]

Hi all, Just leaning about this stuff and want to try to buld up a nice headlamp or two.
Will this driver work for 3 of this Cree XLamp XR-E Q5 White 3W LED Light Emitter, or should I build one for each like?
http://www.ebay.ca/itm/5PCS-Cree-XLamp-XR-E-Q5-White-3W-LED-Light-Emitter-mounted-20mm-Star-PCB-/320941810262?pt=LH_DefaultDomain_0&hash=item4ab99f6256

I would like to power the 3 with a Ryobi 18V drill battery, I also want to build a couple and power them with 3.7V li-ion (I work with computers and have a pile of 18650 batteries from laptops) so i can put together a few battery sizes.
This is the light design.
http://www.instructables.com/id/Improved-high-power-LED-bike-head-light-with-integ/

[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.

[Maragnus]

It looks like the PQ12RD21 doesn't have an ADJ pin, and is available as separate models of four voltages. Is that still usable in this application?

[jaki001002]

I think thats On/Off control terminal , pin 4. When you put a PWM signal in that pin , the output signal (V) response will be almost the same as input , about frequency . So , you'll get PWM signal with high current for dimming LED brightness . If you want to gain more brighness with the same power , this is good way to do.

[placidus_69]

HI Team,
Can i use a 12V DC running 3x1w led ?

[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.

[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!