How I Added a Glove Box Light to My Truck

Intro:

This is my first Instructable. Forgive the lack of images at the beginning because I was not originally going to do this, but a classmate suggested that I start making these. This instructible will not be a one-fix, no-brainer solution for all; you will need some creativity if you want to duplicate my results for yourself

The need:

My car came without a glove box light but had a hole for one. I looked around the web and couldn't find any place that sold the assembly, so I figured I'd just make one with one of the 10W LEDs I had laying around. The result was pretty satisfactory and the total cost is around $3 (more if you have to buy a heatsink).

Parts:

Desired LED(s) - I used a 10W (because of the 12V drop), I recommend at least 3W (you'll need in series or a resistor) or a small LED bar equivalent of at least 400-500 lumens. Ebay pricing:: Bought in bulk: ~$0.80each | individually: ~$1.30
Compatible Heatsink - "Compatible" in this case means both with your LED and with the room you have above your glove box. You can salvage these from scores of electronics. Otherwise these are typically $5-10 online or at RadioShack.
Thermal Paste - If you work with computers, you should have this laying around. Otherwise, it's $5-10 for a tube.
"Normally-On" Push-Button Switch - got mine at RadioShack (yes, they're still around) for ~$1.00 (way too much, but it's of decent quality). "Normally-on" means it will conduct when depressed and, in this case, turn off your LED when the glove box door is closed.
Screws - Both for mounting your LED on the heatsink and mounting your heatsink on the glove box. I will assume most people have a decent collection of these. Otherwise, take your parts to a hardware store until you find something that matches the holes in the LED and the spacing of the fins on your heatsink (or smaller).
Smallish Wire - You can use large gauge wire if you want I guess, but it's completely unnecessary. I used small-gauge speaker wire, but anything flexible (and solderable) will work.
Optional Wire Nuts - I used just one (small gauge).
Optional Electrical Tape - Helps keep contacts away from heatsink and can be used in place of solder

Equipment:

Drill - Necessary.
Bits - Necessary. Sized slightly larger than your selected mounting screws
Table saw - Optional. Needed in conjunction with a metal cutting blade if you need to trim your heatsink (like I did)
Screwdriver - Necessary. Used to install your screws and take your glove box apart.
Allen Wrench Set - Almost undoubtedly needed to take your glove compartment apart.
Soldering Iron + Rosin-Core Solder - Highly Recommended. (To secure your wire to the switch and LED)

Step 1: Drilling Holes + Attaching LED to Heatsink

Begin.

Drill holes in your heatsink to correspond to where you want holes in the top of your glove box (Image 1, 2)
Place LED and drill holes for mounting screws of LED (Image 1)
Screw in the LED via mounting holes you just drilled and apply electrical tape under each contact (oh, I forgot you might need scissors) (Image 1)
Cut off a few inches of speaker wire and peel the two sides of it apart. (Image 3, 4)
Tin your wire BEFORE trying to attach them to the LED (Image 4)
Apply a small amount of solder to both terminals of the LED (Image 5)
Solder the wire to the LED and test the connection by holding the whole thing by it's newly attached wires (Image 6)

Step 2: Install the Switch + Prep for Heatsink

Starting the Install.

Install your switch.

This is the hardest part because it is mandatory that the door closes on it hard enough to activate the light, but not too hard as to not be able to close. Pick a balanced point on the lip, line up your door to make sure it reaches, and drill your hole sized to the threaded part of the switch. I had to use a couple nuts to make the distance perfect. See the images.

This again is very important that you do right the first time and is vehicle independent so I cannot be of more help; the rest is up to you. Quadruple check yourself before making the hole, and start with the smaller bit first if two look like they are big enough to fit the threads through.

2. Once the switch is installed, check and see if your heatsink makes the clearance for your LED to poke through. [My truck already had a spot for a light {if you skipped the into}. If it doesn't, you will need to cut a hole for it. A Dremel would be best for this.] My heatsink did not, it was too big, so I had to cut it. (Image 3) I'm going to assume the audience knows how to use a table saw to cut metal and move on.

Step 3: Install the Heatsink

HeAtSHYNCs arRR CeWel.

Recap: Assuming you've done the previous steps correctly, you now have a heatsink that fits, your LED showing through a hole (Image 3), and overall something like Image 2. This step is for you to take a breath and make adjustments if needed.
As you can see in Image 1, my original holes drilled were not going to work, so I drilled another set, that allowed for better attachment to the glove box chassis.
Drill through glove box chassis with your appropriate holes, and secure it by screwing the screws from the bottom. If you do it through the top, don't blame me if you cut yourself on the tip of a screw in the near future.
Attach one of the leads from your LED to a lead of the switch. Optional: Solder the leads for permanent hold. I highly recommend doing this, despite the nuisance of hauling a soldering iron to the garage and finding an extension cord. Don't burn your seats.
Solder a long wire to the other end of the switch and one to the other lead from the LED. Pay attention to which wire is positive and which is negative. (I always make the wire with the stripe negative). These will be the wires you use to power it, so leave plenty of slack.

Step 4: Test It + Finish It!

ERMYGEERD ISSOBEUUTIIFERL.

Run your "power" wires through somewhere where they won't get kicked and chose a power location. Choosing your battery itself is probably not the best choice. I just used an amp I had pre-wired under my passenger seat.
Put everything back together (Image 1)
Test your circuit by opening the glove box and attaching your "power" wires to their power source. If it doesn't work, be sure to switch the orientation of the wires before deciding you did something wrong. Leave a comment if it still doesn't work, and I'll do my best to help out.
If all is well, hide your power wires under the carpet or however you feel. I take my car apart quite often, so I will hide mine in the sideguard later (Image 4)
Rejoice!(Image 3)

Final Note: This write-up took longer than the actual project.

EDIT 1 [ 5/6/2014]: Shortly after writing this, I realized the 10W LED was getting hotter than expected, even at car off 12.7V. Since I've seen as high as 14.8V on mine while it's on, I decided something needed to be done to drop the voltage. I made a discovery. My LED is still surprisingly bright (probably about 60%, ~550 lumens) at a mere 9V, drawing a mere 0.060A of it's rated 1.050A. It also became extremely cool to the touch and at this point probably wouldn't even need a heatsink. To achieve this, I wired two 1/4W 330ohm resistors in parallel and then those in series with the LED. Voltage of the LED is now 8.7V achieving a mere 25mA draw terminal voltage and keeping (what I would guess to be) a 400-500 lumen output (which I actually like better). This kinda defeats the purpose of using a high power LED in the first place, but now there is the option of choosing how bright of a source you want - all that needs to be cared for is the wattage of the resistors. For instance, if you simply wanted to drive the 10W at 12V max assuming a 14.8V max, 14.8V-12V=2.8V. 2.8V/1050mA = 2.67 ohms. P = (2.8V^2)/2.67ohms = ~3W, so you would need a 3ohm, 5W resistor (which are about $1 each on eBay). There are, of course, many more efficient ways of driving such an LED, but this project was focused on simplicity and was time and money restrained.