120V LED Bulb on 12VDC, 190MA. the Hack

I wanted a 12 volt lightbulb For my home RE system that looked and functioned like a normal light, brightness etc. But one that didnt use a lot of power. I found these at LOWES for under $10 and decided it was time to hack:)

Step 1: The Guts of the Typical LED Lightbulb

Well here it is, bunches of LED's.  First thing you probably want to do is measure where the power is being delivered to the board. In my case it was 30VDC.  BE CAREFUL not to look at the lights when lit.  Also take a voltage reading across ONE LED while its powered on. 

Step 2: Preparing the LED Board for Conversion:)

This bulb ran on 30 volts, so with a little math: 30 divided by 3.25v (single led) you get 9 ish. since we have 18 led's in this light, it means theres 2 strings of series wired groups.  This can help in isolating the proper LED's for groups of 4 each.  Since one series of 9 LED's is already wired together, you can divide it in half. Running on 12vdc, each single LED will be at 3volts.  Run your groups of 4 led's in parallel to eachother (in this case that gives us 4 groups) What to do with the remaining 2 led's? Isolate them and either wire in resistance to run 2 led's on 12vdc and wire them parallel to the other groups, or do what i did and wire it seperate for a night light:)  Also since the math tells me that there are already 2 strings on this board, there is a common point between them.  Look for that and build from there.  Trust me, find this first, it makes figuring trace cuts etc MUCH easier lol  Start at V +

Next is the pain in the azz part. Carefully cutting the right traces and soldering everything up:)  Ill assume you have these skills already so i wont bore you with the details of that task. Plenty of instructables here to teach you if you dont:)

Step 3: Finger Power!

To test each group when you have the proper traces cut and soldered, use your finger. Hook your body in series with your test string and use a small screw driver or probe to apply power. You wont run the risk of frying your LED's if you made a mistake (trust me you will, i fried 2 legs on my first light before i got my technique right lol)  They dont light up bright obviously, but you can see if there are any problems.

Step 4: Now Apply Power

There ya go, first string dont, pretty

Step 5: Now Finish Up the Soldering/wiring

now its time to wire up the rest. I chose to keep all the strings seperate to make them easy to dim. Just switch on 1 2 3 or 4 strings and you get dimming without need for a dimming circuit. 

Step 6:

There ya go.  A 12vdc 40W light bulb that only uses 190ma.  The possibilities for this bulb are endless.  Hope i at least gave you some ideas:)

Comments

[nicksrandomlogin]

Nice hack. I just took one apart before I read this. Mine uses 94V for 8 LEDS. One LED in my single chain had broken. Using a Voltmeter across the LEDs I found the dead one, the Voltmeter current was enough to illuminate the 7 remaining good ones slightly and the open circuit voltage was 120V DC.. Using the current meter across the dead one I got 140 mA and the 7 were nice and bright. After further destruction, I got the circuit board out and that was labelled 94V. So we are talking each LED taking 11.75V (12V nominal) and ~ 120 mA.

The tip - is not to forget about the power dissipation. The LEDS are mounted on a metal plate which is screwed onto a heat sink (with some thermal compound between) that goes inside the lamp conical back shell. It gets HOT!!!
Don't operate them without this except for very short times for testing.

[PhilS.]

if you have a Dollar Tree store nearby, they have LED bulbs for a dollar, 9wats for 60 watt output.. OK go play lol

[CoolWaysToSaveThePlanet]

It's near 2016. Any changes in LED AC bulbs that might modify this procedure? I've heard "we're now in third or fourth generation" LED bulbs for household use.

[52193]

the only bulbs i can find deliver 65V through a single series of LEDs and incorporates a very small SMD thermistor on the thin double sided copper heatsink(pcb epoxy type material between both sides) to regulate the current. Does anybody have any idea how to re-arrange the LEDs to be on one side or how to arrange them on a different board without them shorting on a new aluminum heat sink. the bulb type is philips 800 lumen dimmable 10.5W 95mA bulb with 9290002709(serial no.?). This instructible is great. It is nice to finally find some useable information. It has 20 LEDs. Thanks.

[mrx23dot]

Are there any 12V LEDs avalabile with passive heatsink? If I don't want to do any work, only connect my constant current PSU?

[dabaddon]

U r amazing sir, just what ive been looking for. Since i just purchased some 5730 panels, wondering how the hell. Im suppose to powerup with

[azmanyaacob1]

I'm in the making of 12Vdc lighting system at home - friendly reminder if battery is a power source (in my case - I use seal lead acid) , please consider to put a low voltage disconnect circuit between 12vdc source & load. Frequent discharge down below 10V will eventually damage the battery.

[liquidhandwash]

good job on the instuctable, I don't mean to be picky but, if the light consumes 190ma @ 12volts then it would be a 2.28 watt light bulb, as watts is a measure of the power consumption not light output.
Thats not a bad thing, I think you mean it has the same light output as a 40watt incandescent light bulb.

[HawaiianGuy]

You are correct:) Thats the beauty of LED vs. incandescent bulbs. Its light output is like that of a 40w bulb, but consumes only 2.3ish watts. And i can attest to the brightness, next to a regular 40w bulb, its pretty close. Its light output seems a little "whiter" but its plenty bright.