High Power LED Tutorial #1 – How to Drive 1W and 3W LEDs from 12 Volts


High power LEDs differ from regular LEDs in a number of respects. Firstly, current regulation using resistors is impractical so it’s necessary to use a switched mode voltage and current regulator. Secondly, they generate heat which must be drawn away from the LED to prevent damage by overheating.

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  1. The accurate power supply control to the led is interesting and the problems caused by the alternator kicking in on a car to charge the battery. In car specific led exchange bulbs do they have any sort of regulation or resistance on board and are they doomed to failure more rapidly than the incandescent filament?

  2. Hello Julian

    i've purchased the same voltage and current regulator to drive 3w leds , i' ve set the voltage to 3.3 v and the current to 700 mA as instructed on the data sheet however the led only drew 200 mA am i doing something wrong or it's just the quality of the leds . it's mounted on an aluminum heat sink and i got an additional heat sink but it did not heat up can you kindly advise ?

  3. can't you just stick a coil in series? any sudden change in current like a massive spike would cause a voltage drop across it and save the leds? 😀

  4. Went through full loud shooting apes in the internet jungle, started being desperately entangled in inextricable intellectual porridge, then sinking stuck in quicksand thought when i saw the regulated Led light….Tarzan julian saved me…
    Thank you a lot! that's one good tutorial.

  5. Awesome information! In the process of designing custom shaped turn signals and brake light for my motorcycle. So this helps immensely with the wiring issue.

  6. Great video! I like that screwdriver cover for those annoying screw slots. I think I'll start using small alligator clip covers like that.

  7. Very surprised you don't have an Amazone link in the description as you'd earn money just from people browsing there, as long as the cookie stayed ni their cache for 24 hours.

  8. At 06:47 where the matrix led are powered that way, will both string of 3 series leds get 300mA each equally ? Or will one series led draw a different amount of current ?

  9. A few words of caution, I have recently bought a current and voltage controlled circuit off E-bay, I wanted to push a constant 150 mA of current through 6 luxeon LEDs from a 12 volt DC battery supply, underdriving them by a long way and cooling them with oversized Aluminium heat sinks because I want them to last virtually forever.
    I carefully set up the circuit to limit current to 150 mA and the voltage was set well within limits.
    However, I made the fatal mistake of hooking up the power to the circuit and then connecting the LEDs to the circuit.
    This created a sudden surge and pop went one of the Red Luxeons, not much of a problem normally just replace it, except the LEDs were carefully installed on heat sinks behind tongue and groove wood panelling, the whole episode cost me a days work.
    Finally, I decided to use a voltage boosting circuit only and run it through an LM317 circuit I built a while back to limit the current, again a big word of WARNING here, avoid the simple ONE resistor only LM317 current limiting circuits, build one with a potential divider as I did.
    Because I bench tested on breadboard a simple LM317 circuit with a single power resistor and the damn thing allowed an initial surge of around 2 AMPs before settling down to the required current flow.
    In summing up the whole experience was dreadful and I hope I can save someone similar problems, always hook up the LED side first before powering up, check and check again on a bench test first before you even get to that stage, one more thing I did after this incident is I installed a 100uf 25-volt Tantalum Capacitor across the plus and minus rails to the LEDs, on powering up this effectively causes a momentary short circuit across the LEDs, forming a shock absorber to buffer any current surges.
    Bear in mind a capacitor across the LED supply rails could make things worse if you were to power up and then connect the LEDs up downstream of the Capacitor.
    I hope I have helped people avoid the problems I have just had to solve.

  10. Hi, could i add a mosfet to the wires going to the 1 watt led as i need to feed the owtput from a pwm
    Board to make the led 1.5 kz with a duty cycle of on 7 off 1 , this is for a 1970's british army infrared
    Intrusion alarm set called IRIS i was given which only had 1 ir transmitter , i have made the system work with the pwm board and a 10 mm 850 nm led
    With resistor but will use 1 watt 940 nm led's
    To make 4 ir transmitters which need more current than the pwm board's can take.

  11. Hi Julian,

    Firstly, may I compliment you on your videos. Of all the electronics videos I have watched to date on YouTube yours are by far the best. Not only are you extremely clear and concise in you explanation of everything, but equally you ensure that what is important is shown on camera. I am slowly working my way through all you videos as they are a wonderful resource for so many, at all abilities.

    I am now unfortunately disabled and have been looking for a hobby I can manage from my wheelchair, electronics appears to be the ideal thing but I am very much a beginner. I’m sorry to be cheeky but I wondered if I could ask you for some advice please…my little grandson has a 12v battery powered “sit on” car and although I will not be able to fit everything myself I want to build a LED lighting project that my son in law can fit.

    I saw a video a while ago that shows the functionality that I would love to achieve and tried contacting the author. Unfortunately he is probably a very busy man and failed to respond. The video link is here: https://m.youtube.com/watch?v=pD-InblYDlk

    He mentions buck converters which I have investigated, but based on the type of small battery installed in these toys my research thus far seems to indicate think maybe buck/boost (or is it boost/buck) would be more suitable. With my very limited knowledge I have looked everywhere I can think of but cannot find one suitable so was therefore wondering if you could please possibly advise me accordingly as clearly you know this stuff inside out?

    The criteria that I am aware of appears to show the following considerations…

    1. 12v battery Vin (I would guess this would vary as the battery is run down by use)
    2. be as efficient as possible to minimise drain on the battery
    3. have the ability to set both output voltage and amperage
    4. be Arduino controlled so needs some form of “enable” or “switch” control
    5. due to possible issues with heat I am guessing that 1w LEDs will be the brightest type I can use, and as his car only has 2 lenses on the front I’m envisaging that the largest circuit will consist of just 2 of these 1W LEDS.

    I’m guessing you’re a busy man too and although it’s going to take me a long time to figure all this out, simply by knowing which buck/boost converter to use will help more than you know., and based on some of the comments on the video previously mentioned, plus all the other online videos showing similar projects I think you could make a fortune if you designed and sold a schematic and/or circuit diagram for such a project.

    Sorry to bore you with all this but I’ll keep my fingers crossed you kindly reply. Thanks.

    Kind regards,


    PS. Could you also please possibly list the 3 boards shown in this particular video? Thank you again

  12. Excellent video and explanation, but could anyone tell me, if you were to use a CONSTANT VOLTAGE supply adjusted in such a way that a fixed amount string of Luxeon LEDs or indeed a COB type LED is passing much less than its rated current, let's say 200mA through a string of 1 watt Luxeons, which is well below the 350mA rating. Is there a problem with doing things this way? providing the voltage is adjusted low enough to prevent excess current flow.
    Baring in mind that even temperature variations in the LEDs probably would not be enough to push the current much past the 200mA that is flowing, and certainly nowhere near 350mA.

  13. Thanks for the video, I am making a UV resin curing lamp. How come you did not try 4 LED 3 watt lamps in series from the 12v battery? Did you give it a try? The bulbs I got were 3.2 to 3.4 volts

  14. So if I wanted to drive 16: 1 watt leds with an arduino, I would need 4 constant current drivers and a transistor to switch each one on from the arduino pins?

  15. Your tutorial is awesome! Does this mean If I use 4 LED with 3V each on a 12 V Battery, I don´t need some resistors?

  16. But how can i dim it with a MCU? I don't think a mosfet on the output or input would work or be a good idea.

  17. You skipped the part where you say you set the voltage to 3.3V for the single led setup.
    Other than that truly great video and explanation. Cheers!

  18. Ok……I bought some drivers on Ebay and they work good for 3w led's, which it says they are rated for. I think that the specs they give are wrong? Here is copy and paste from listing Also, these are NOT adjustable. ……Input Voltage: DC/AC 12
    Rated voltage: 6-12VDC
    Frequency: 47HZ-63HZ
    Output Current: 300mA±5%
    Efficiency: ≥92%
    PCBA(L*W*H): 18*12*13mm
    Drive power: 1*3W…….
    I'm seeing more like 800ma current draw. So, these specs are wrong, correct?

    Next question…I ordered some other ones that say good for 1 to 5 1w led's. Do these possibly have some built in feedback to adjust voltage? I have not received them yet but they look the same. These drivers are driving me nuts!!!!!! : )

  19. Hi Julian.
    I got chinese 3W beads from aliexpress.
    using small buck-conv. with one trimmer on it:
    I set it to 3.4V, than measure Current to be 50mA (0.05A) , R = 3.4/0.05=68ohm.
    To list :
    2.4V/0A=99k dark led;
    3V/0.025=120 ;
    3.2V untested ;
    3.4V/0.05=68 (if 48.5mA R=70. 3% delta);
    3.6/0.6=60 ;
    3.8/0.075=50 ;
    3.9/0.087=45 (if 97mA R=40. 11.5% delta ).
    1. unsmooth form of R line
    2. NOWHERE NEAR 300mA in your Ohm Law calc.
    could you enlighten US ?


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