12v LED Lights for Car, Home, Boat......




About: Fast, Good, Cheap..... I CHOOSE ALL!!

Hi this is a way to make 12v led lights that can be used on any standard 2 pin 12 volt light for example your cars lights, inside your motorhome, boat or 12v home lights(like those for your desk or to light up your paintings or photos).. these are very common so you can replace them almost anywhere and are also very very cheap easy to make and you will be saving lots of electricity since they bearly consume any electricity..

you can make these of 4 or 2 leds or more if conecting them in parallel depending on size and how much light you will need

it pretty much ends up beeng the size of a small 12v car bulb

Step 1: Parts!!!

the parts for this project are as following

you will need (in picture)
1---- 100nf capasitor
1---- ln4007 diod
1---- 150ohm resistor **
4---- super bright white leds (i will be using some bright orange LEDs)  *

soldering iron

   * this is to make the 4 led version... if you want the 2 leds you will need a 348 ohm resistor instead

  ** the value of the resistor will also very with the input Voltage, the type of LED you buy and the Diod...
      my led has a Forward Voltage of 2V (the white ones are 3.5V or somthing like that) and a max of 20 miliAmpers and my diod of 1.1V and i think a max of 1amp
      so if you would like to calculate the exact value for your components you will need this information..

     In the images i leave you a formula to calculate the resistor depending on your components..

     in this formula (in the image)
     V--------- is the voltage you will use to power the led
     Vfled---- is the forward voltage of your led
    Vfd------- is the forward voltage of your diod
     Imax---- is the maximum voltage that your circuit can take so that would be your LEDs operation current
     nºleds-- is the number of leds you will be conecting(if the resistor gives a negative number you passed the limit of leds)

Step 2: Circuit

the circuit is very simple just a bunch of leds in series with a diod to protect from any reverse voltages and a capasitor to filtrer any large spikes that can burn out the leds (Cars have many) and a resistor to limit the current .. the capasitor is optional but i recomend it specialy if its going on a car...

in the image you can see the circuit for a 4 led light with all the calculations..

((typo the image has to say 100nf capasitor not 1nf))

Step 3: Puting It All Together Step1

now for the fun part!!!!!

first some things you have to know... the short pin of the led is the negative (anode) end it also has a mark on the outside of the led..
on the diod the side without a shaded line is the negative (anode) side....

Start by soldering the resistor and the led as shown in image
the resistor is soldered to the catode(long pin) of the led

Step 4: Put It Together Step2

now we have to bend the catode of the new led and the anode of the one we just soldered and solder them together..
and remove the exces metal (dont cut the anode of the other led!!!) do this with all three.. and ditribute them in a squre...

Step 5: Put It Together Step 3

now you will have to bend the resistor to the other side so it takes up less space and solde the diod in series with the resistor...

after that you will have to solder the capasitor to the resistor (where the diod is conected) and the anode of the last led... (if you are lost just follow the schematics) (WARNING!!! dont hold the soldering iron to long or everything will fall apart!!!) and remove al extra metal


Step 6: Finish and Enjoy!!!

you are done.. now just stick them wherever you have 12V (or wahtever voltage you calculated)

note: if it does not light up you might of conected it backwords ( dont worry the diod protects it from burning if conected backwords, just dont leave it to long backwords it may get damaged)

-change those always burning out lights from your car  (LEDS HAVE A VERY VERY VERY LONG LIFESPAN)
-light up your car interioir
-make your car into a Fast and Furious neon(LED) light tunner AWSOMNESS!!..
-light up your gaden!!  (insulate the leds first!!)
-light up your pool!!  (at own risk)
-tranasform your motorhome or boat into low consumption LED ilumination...

controll them with a microcontroller
(these orange ones on the video are the ones i made and calculated for this instructable the white leds from the photos had 4.5V forward voltage so a diferent resistor was used and they were very bright!!!!!...)

any thing that can plug in a 2 pin 12v bulbs will work.. almost all car headlights and interior lights can use this and those 12v home interior lights..

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29 Discussions


2 years ago

Just made this on some breadboard to try out a new power supply. Used 1W LEDs(2) works great now going to prepare another one to replace bulbs on my caravan!!!

Brill and thanks for the solution I've been looking for all day..


8 years ago on Introduction

I didn't rate it yet, but it is very nice, good luck in the contest, Have a look at my entry Star-Wars X-Wing 2 for the contest.
Well done again on making it!!!

1 reply

Reply 2 years ago

use one resistor and a varistor to limit on 12 Volt.


5 years ago

crap i forgot the charging system puts out 14.4v good to know. but once I'm done with my math how do i get the resistor value

1 reply

Reply 3 years ago

Ajensen27, did you get the info you asked for? I am also building a fixture fir 14.4 and would like the same info.


3 years ago

100uf capicitor burned up after 1 minute. Could i have installed backwards?? Or did i use wrong capacitor. Nf vs Uf??? Please help!


3 years ago

Hi there i m unable to get the correct value of ohms can you help me out. The stuff i am using is.
12 V current.
8mm 3.4 to 3.7 volt leds
Please tell me which diode, resistor and capasitor should i connect with it. I want to use this in my car fog lights.


3 years ago

How can i download ???????????


7 years ago on Step 2

Nice project. I use on my car only 1 rezistor with 3 leds / module and i calculated for 14.4V. (I put them in serial.)
Your ideea with diode and a capacitor is great but how do i calculate or what models can i use?

1 reply

3 years ago on Introduction

It would be better if you gave the circuit diagram of the same. I can be wonderfully used for emergency lighting.


4 years ago on Introduction

Are you sure about anode & catode? Usualy long is anode, short is catode(and marked outside)


4 years ago on Introduction

You mean connect the LEDs in series, not parallel.


4 years ago on Introduction

Great stuff. I made a LED light for a licence plate illuminator a while back but soon got burned. Now I see that adding a diode and a capacitor solves that problem in long term. However I have a question regarding cap value. Must it be exactly 100pF or can I use something larger, say .1uF? It's because I normally don't buy electronic parts, I salvage them mostly from old electronics and from what I currently have on my hands, I'm unable to find a 100pF cap.


4 years ago on Introduction

I made two lamps with this instructable.

It works fine !

To replace a T10 5w lamp, i connected to a piece of test board (3 lines width) cutted with dremel tool.

(sorry for my bad english...) ;-)


5 years ago on Step 2

Is this image correct and helpful?


7 years ago on Step 2

why is the diode neccesary? the LED's are diodes, surely they will only allow current to flow one way, or am I missing something?


7 years ago on Step 6

I had a question what is the purpose of the Diode since the LED are also diodes they wont let you hook them up backwards anyways. Are you using the diode to cut the voltage down along with the resistor?

1 reply

Reply 7 years ago on Introduction

LEDs typically have very low reverse breakdown, on the order of 18-20 volts. If one is using, say, a 24VDC supply and were to hook the LED up in reverse, it would surely destroy the LED. When using an AC supply, this can be somewhat mitigated by using two LEDs in anti-parallel so that one of them is conducting on each half-cycle, and the reverse voltage that the "off" LED sees is never greater than the forward voltage of the "on" LED, about 0.6V to 2V, depending on LED type. Vehicle charging systems are prone to "load dump", where the reverse voltage can briefly spike to 50 volts, or more, as when the engine stalls or is turned off. Having a 100V to 200V diode in series with the LED will prevent the LED from being destroyed by a reverse current spike.