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Following the foot steps of the CFL, we are starting to see LED lamps showing up at the landfills because they didn't live up to the claimed 25 years of life. Typically these LED lamps died because of the failure in the power supply circuit, while the LED modules are still fine. I recently had two LED flood lamps died with only 3 years of use. Rather than throwing them into the electronics recycling bin, I decided to upcycle them into something useful. My eventual goal is to couple these lamps to the pattern generator section of the MSO-19 to create a variable delay strobe for high speed photography. Although they are not as efficient as the modern 100 lumens per Watt LED bulb, these lamps still pack quite a bit of light. Stuffed with 39 LEDs per module, it takes quite a bit of voltage to drive these lamps. Fortunately I had a -48V DC telcom power supply sitting on my shelf for the past decade begging for a project. For those of you that don't hoard used electronics. A quick search on the Amazon showed that a 48V DC power supply can be had for less than $20.

I recently use this lamp to demonstrate the concept of PWM in this MSO-19 pattern generator instructional video.

To harvest the LEDs you'll need the following:

  • A dead LED lamp.
  • Simple hand tools to open the lamps.
  • Soldering Iron.
  • Wires.

Additionally to create a digitally controlled LED lamp, you'll need the following:

  • A 48V power supply.
  • Vishay VOM1271T Opto isolated MOSFET driver. Optically isolate the 48V drive voltage from my delicate low voltage electronics. Besides, it comes with a nice turn off circuit to make my life easy.
  • ST STD5NM50, N-channel power MOSFET. I harvested this from a dead laptop power adapter. You can use anything as long as the Vds, Drain-Source Voltage, is higher than 48V.
  • CR2032 Coin cell battery and holder.
  • Push button switch.
  • two 220 ohm resistors.
  • Header pins.
  • A perf board to mount everything.

Step 1: Harvesting the LED Lamps

Depending if you have a flood or a spot lamp the steps are similar.

For flood lamps

  1. Gently slice and pry off the front diffuser.
  2. Mark the + and - side of the LED module, black is -, the other is +.
  3. Desolder the wires.
  4. Unscrew the two mounting screws and remove the lamp base.
  5. Find a suitable fastener and re-attach the reflector. Don't forget to re-apply the thermal paste between the LED module and the aluminium lamp housing.
  6. Solder the power leads to the LED module and pass them through the heat sink.

For Spot lamps

  1. Gently pry off the concentrator lens with a jeweler screwdriver.
  2. Mark the + and - side of the LED module, black is -, the other is +.
  3. Desolder the wires.
  4. Unscrew the two mounting screws and remove the lamp base.
  5. Drill out the two small holes on the plastic cage, indicated by the picture.
  6. Remount everything with 4-40 or 3mm screws and nuts.
  7. Solder the power leads to the LED module and pass them through the heat sink. Don't forget to re-apply the thermal paste between the LED module and the aluminium lamp housing.

Step 2: Building the Control Circuit

Follow the attached schematic to wire up the LED control circuit. It's an easy circuit, there aren't that many connections. Just double check all the connections and polarities before you power the lamp up. The CR2032 battery and the push button switch are there so you can manually trigger LED Lamp without an external voltage source.

Step 3: What's Next

The opto isolated MOSFET driver is basically an IR LED. Any voltage that turns on a LED will turn the MOSFET driver on. Subsequently, the Power MOSFET will also turn on and power up the LED lamp.

You can easily control the LED lamp with an Arduino, it will behave like any LED, just insanely BRIGHT!!! I'll be using this LED lamp as the basis for other instructable projects in the future.

<p>I like the idea of re-cycling dead lamps with a new power supply, but really don't understand the utility of a CR2032 battery... a resistor from the 48V would be more (eco)logical, if really a control mosfet is needed. Another thing to keep in mind for the lifetime of a power LED is the cooling. A not well cooled LED will see it's lifetime dramatically shortened.</p>
<p>The CR2032 and the push button switch are there to provide manual triggering of the LED Lamp. In order to maintain isolation between the low voltage side and the high voltage side, i decided not to draw any juice from the high voltage side to trigger the MOSFET driver. It is also possible to strap a few of these lamps in series and use a MOSFET with a higher Vds to drive these lamps directly from rectified line voltage and skip 48V power supply altogether. One can probably harvest all the rectification circuitry from a PC power supply, two diodes and a cap. Caveat is the potential safety issue playing with line voltage. The massive aluminium housing originally engineered with the lamp should provide all the cooling the lamp needs. If it gets too hot, one can always attach a heatsink fan to the fins.</p>

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Bio: Lifelong tinkerer.
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