Introduction: Hack an Expensive LED Bulb to Fit (nearly) Anywhere!
LED lights are modern marvels but are fitted into antiquated packages meant to be retrofitted into stone-age fixtures. Whose idea was it anyway to cram space age technology into a bulb invented 100 years ago?! My problem was replacing a dim, halogen bulb illuminating a ceiling fan. The new light had to be:
- Much brighter than the existing 100W halogen bulb
- Low profile to fit in the limited space behind the cover
Nothing was available off the shelf though Amazon once had a light kit that included LEDs fitted to a large thin disc made to be retrofitted into ceiling fans, though, even that was undimmable, and not likely to have been bright enough anyway.
So, I did what any unsatisfied consumer does when confronted with inferior solutions: I hacked it! Here's how and why I did what I did....
Step 1: Find and Break a Bulb... Option #1
For this option, I used a 240 watt equivalent LED bulb. It's a hefty, solidly built, and expensive bulb made for outdoor use. Big box stores have them for about $40. Let's get to the four main components of (any) pre-packaged LED lamp:
- Heat Sink: All LEDs generate heat and this light generates quite a bit of it that has to be dissipated. In this case, the white aluminum housing acts as a heat sink, though a passive one.
- Lens: The clear faceted plastic lens acts to focus the emitted light into a useful beam. I won't need it here, but you may wish to use yours, so, be careful when dismantling your lamp as this soft plastic scratches easily.
- Driver: The real meat of an LED lamp is the sophisticated electronics that supplies clean, regulated power to the diode. In this case case, the driver has been potted with a soft, white, easily removable silicone epoxy.
- LED: The small yellow circular film embedded in the center of the heat sink is the LED. Thermally conductive paste keeps it loosely glued to the head sink. This is the same kind of paste that help draw heat out of a computer's CPU and into it's surrounding heat sink.
Let's take this thing apart!
- Use a thin flat screwdriver to release the concealer ring and reveal the holding screws behind it.
- Remove the lens and set aside for re-use, if necessary.
- Remove the next concealer plate around the LED.
- Cut the supply wires to the LED leaving a bit of insulation on so that you can easily maintain polarity when re-wiring later
- Unscrew the driver from the back of the heat sink/housing.
Step 2: Find and Break a Bulb... Option #2
In this option, I took a "wet location" 120W equivalent outdoor bulb apart. Unlike the bulb in option #1, prior, this bulb is glass enclosed, and about half the price.
- The front face of the bulb has been glued to the glass housing and can't be removed without breaking it. Crack it carefully, then remove pieces with pliers. Wear gloves and eye protection!
- Remove the rest of the housing. In this bulb, heat conducting paste lines the contact between the reflector and the glass housing, turning the housing itself into a heat sink, albeit a pretty ineffective one.
- Unscrew the driver, cut the LED supply wires, and set the reflector aside.
Step 3: Unpot the Driver (Option #1)
I needed the driver to fit into a pretty tight space. You might not have the same limitation, in which case, you might not need to unpot the driver. You will, however, need to remove the screw base to access the line voltage supply wires.
- The plastic lamp base needs to be scored so that it can be easily removed. I used a Dremel with a cut-off wheel and scored the plastic just deep enough to penetrate the plastic without damaging the underlying electronics.
- Use a flat screwdriver to pry apart the plastic halves, then peel 'em apart like a banana!
- Some part of the potting compound may be easily removed, like this one was; simply remove it gently....
- The top part of the driver will require careful epoxy removal. Give this job to someone who likes to pick scabs. Use fine tweezers, or nut picks to gently remove the epoxy. Be patient and plan on 15-30 minutes for this job.
- Once done, carefully inspect your work for any damage. Did you remember the polarity of the wiring at the line supply end?
Step 4: Unpot the Driver (Option #2)
The process for unpotting this driver isn't very different than that on the previous page:
- Carefully score the plastic housing with a Dremel and cut-off wheel.
- Gently peel off the housing material.
- Carefully pry out the soft epoxy.
- Check for damage.
Step 5: Modify Your Heat Sink
The heat sink is very important as it lengthens the lifetime of the LED by carrying heat away from the back of the diode. In many cases, the bulb housing does double duty as heat sink. If you remove it, you'll have to replace it with some other way to get heat off the back of the diode. Some high quality, small-profile bulbs come with an integrated cooling fan that blows heat off the diode. Again, the Dremel comes to the rescue:
- Remove the LED from the heat sink.
- Figure out some way to efficiently re-use whatever part of the existing heat sink you want. I tried a couple of different ways to modify the existing sink for my application until I finally decided that I really only wanted to use the LED holder without the surrounding materials.
- The holder/sink must make intimate contact with the rest of your sink. I used an ordinary belt sander with 120 grit belt to remove excess aluminum from the back of this heat sink. Then, I polished it smooth with 400 grit waterproof sandpaper.
- Once it has been polished smooth, coat it with thermal paste. It is now ready for installation of the other part of the heat sink.
A note about heat...
This light gets pretty hot. The housing does a good job of conducting heat away from the back of the LED, but that's as far as it goes: now that the housing is toasty hot, it counts on the surrounding air to move heat off of itself through convection and conduction, and, if there's a breeze or rain, advection. It's not a very efficient system as the housing also acts to heat up the driver, insulated snugly in its silicone cocoon. Now that you have liberated and separated all of these components, you should think about getting that heat off of the LED and keeping it away from the driver! Perhaps your new configuration will be more efficient than the original!
Step 6: Custom Re-Assembly
For this project, I retrofitted the LED and driver to an old halogen light fixture on the bottom of a ceiling fan. I didn't have to worry about heating this thing up any more than the old halogen bulb did. Importantly, the integrated dimmer switch worked perfectly with this new LED retrofit.
Click on each of the photos for better detail.
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