Introduction: DIY LED Dome Light (updated 9-15-09)

My little Honda Del Sol was in need of a brighter dome light. I went from regular bulb to a manufactured LED replacement to finally one high brightness one that I can even read with.

Step 1: Bit of Caution

These LEDs do get HOT. Normal opening and closing the doors do not allow the LEDs to get very hot. Just do not do what I did and leave the car door open for several hours. The hot glue and epoxy melted into the lense of the dome light and the LEDs got heat damaged. They still are bright, but not as strong as they where.

Step 2: Tools/ Items Needed

Tools

  • solderering iron
  • solder
  • Helping Hands would call it a must have for this
  • hot glue gun (extra stick)

Items
  • 9x white special square type multi chip LEDs Very High Brightness ( I used 50,000 MCD 140* 100mA) I recommend these. They are what I used. $18 for 30.
  • 3x 22 ohms (red red black) 1/2 watt resisters.

Step 3: Soldering LEDS

Solder LEDs in rows of 3. The Idea is to curve the LEDs joining the legs together wile the side of the LEDs are touching.

On these LEDs the positive anode is the strait leg. The negative cathode is the blade/heat sink fin thingy.

Step 4: Solder the Rows Together

Line them up so that they are side by side and solder the inner negatives together at the end.

This might take a few tries to do.

Step 5: Attach Ground

Solder a piece of wire for the ground connecting all of the negatives of the LEDs

Step 6: Adding Power

Bend the end of the resister like as show in the picture and clip a part of the end leaving a little.

Clip off every other power connector on the first LED in each row.

Solder the bend end of the resister to the led keeping the resister as close to the LED as possible.

Twist the ends of the resister together with a piece of wire and solder together.

Step 7: Adding Hot Glue for Preventing Shorts

Apply hot glue to the bottom of the LEDs covering all of the pins.and exposed wires of the resisters.

Step 8: Testing

12 volts is what a car uses if you have a 12v wall wart use that for testing. If you don't have a spare or a available 12v DC power supply. A simple 9 volt battery will provide enough to power the light, but it will be dim.

Step 9: Comparison to Other LED Car Light

This is the LED car light that I bought compared to the LED light that I made.

So far size wise it is bigger.

I need to get a better picture from inside the car, The digital camera does not snow much in the dark even with how bright this light is.

I did try using it as a headlight on a 4 wheeler. It worked better then I thought it would.

Step 10: Afterthought

After looking at this light I have thought of a few more ideas for using it.

  • desk light replacement
  • trunk/ boot light
  • flashlight
  • reading light

Comments

author
opliko (author)2009-05-19

I would like to add that most modern cars use 13.4 volts, not 12, so make your own calculations accordingly. That is of course from a fresh battery. I find it easier to over estimate the cars' power than under, it makes it a little safer and your light will last longer!

author
indivara (author)2009-01-13

I tried replacing the dome light in my car (also a Honda) with LEDs, but instead of making it myself, I bought a ready-made one (3 x 3 grid, same as yours). Unfortunately, it refused to light up in the winter, probably couldn't stand the low temperature.

You should probably consider including the schematic diagram, will make it easier to understand the wiring. The one below, I created using the freeware version of Eagle (use it if you like...)
http://www.cadsoft.de/index.htm

How did you calculate the resistor values? What is the forward voltage drop of the LEDs you've recommended? The seller on ebay doesn't say.
Since you've used a 22 ohm resistor with three 100mA LEDs in series, that would make 2.2V across the resistor, leaving 9.8V (12 - 2.2) across all 3 LEDs, making it around 3.25V (9.8 / 3) for each LED.

How good was the heat dissipation once you hot-glued all the components? Wasn't there any overheating of the LEDs?

LED dome light schematic.png
author
Rob K (author)indivara2009-01-13

Thanks for the advice. I will put the schematic up.

The 22 ohm value I got from http://led.linear1.org/led.wiz using 3 LEDs at 3.4fV,100mA at 12v. Using 3.6fV the resister value was at 12 ohms. For some reason I had a few left over 22 ohm resisters from another project. I used them for this project.

As for the the LEDs over heating. I had used a 14vDC wall wart. This made the hot glue over the pins start to melt and get squishy almost instantly within 2-3 seconds. Using the right voltage 12v and the cars 12v makes the LEDs warm but not too warm to cause a problem. The regular filament bulb was warmer then the LEDs.

author
indivara (author)Rob K2009-01-13

Cool site! Even gives the schematic!

author
JakeTobak (author)2009-01-12

You might want to do the testing before you put on the hot glue.

author
blakkat (author)JakeTobak2009-01-12

You're right Jake Tobak. Nice instructable.

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