Salvaging Working LEDs From “Dead” Light Bulbs

Sure the box said they would last for years or even decades, but anyone who’s picked up some bargain LED bulbs knows the reality is a bit more complicated. Sometimes a few LEDs in the array pop, reducing the overall light output. More commonly, the power supply starts to fail and the bulb begins to flicker or hum. In either event, you end up pulling the bulb and replacing it.

But [Bifferos] thinks we can do a bit better than that. Rather than just chalking it up to poor QA and tossing the bulb, why not do a little exploratory surgery to identify salvageable LEDs in an otherwise “dead” bulb? After pulling apart a couple of burned out bulbs (name brand and otherwise), he was able to pull out an impressive number of handy LED panels that could be easily repurposed. Naturally, with a little more coaxing, the individual SMD LEDs could be liberated and pushed into service as well.

Separate PCBs with banks of LEDs are ideal for reuse.

As you might expect, there are far too many different LED bulbs out there to create a comprehensive teardown guide, but [Bifferos] does provide some tricks to help get the bulb open without hurting yourself or destroying the thing in the process. Once inside, the design of the bulb will dictate what happens next. Bulbs with multiple arrays of LEDs on their own PCBs can be easily broken down, but if there’s just the single board, you may want to pull the LEDs off individually. To that end, the write-up demonstrates efficient methods of stripping the LEDs using either hot air or a pair of soldering irons.

We’ve talked previously about the rather underwhelming performance of modern LED bulbs compared to the manufacturer’s lofty claims. We’d rather see these bulbs designed well enough that they actually live up to their full potential, but the ability to salvage useful components from the failed luminaries at least softens the blow of having to toss them early. Though that’s not the only reason you should disassemble your LED bulbs before you put them in the trash.

Small sensor built into audio jack, held in tweezers

Measuring LED Flicker, With Phototransistor And Audio App

No one likes a flickering light source, but lighting is often dependent on the quality of a building’s main AC power. Light intensity has a close relation to the supply voltage, but bulb type plays a role as well. Incandescent and fluorescent bulbs do not instantly cease emitting the instant power is removed, allowing their output to “coast” somewhat to mask power supply inconsistencies, but LED bulbs can be a different story. LED light output has very little inertia to it, and the quality of both the main AC supply and the bulb’s AC rectifier and filtering will play a big role in the stability of an LED bulb’s output.

Mobile phone spectrum analyzer pointed at light source
The DIY photosensor takes the place of the microphone input.

[Tweepy] wanted to measure and quantify this effect, and found a way to do so with an NPN phototransistor, a resistor, and a 3.5 mm audio plug. The phototransistor and resistor take the place of a microphone plugged into the audio jack of an Android mobile phone, which is running an audio oscilloscope and spectrum analyzer app. The app is meant to work with an audio signal, but it works just as well with [Tweepy]’s DIY photosensor.

Results are simple to interpret; the smoother and fewer the peaks, the better. [Tweepy] did some testing with different lighting solutions and found that the best performer was, perhaps unsurprisingly, a lighting panel intended for photography. The worst performer was an ultra-cheap LED bulb. Not bad for a simple DIY sensor and an existing mobile phone app intended for audio.

Want a closer look at what goes into different LED bulbs and how they tick? We have you covered. Not all LED bulbs are the same, either. Some are stripped to the bone and others are stuffed with unexpected goodness.

Teardown: Bug Zapper Bulb

Up here in the Northern Hemisphere, mosquitoes and other flying pests are the last thing on anyone’s mind right now. The only bug that’s hindering gatherings at the moment goes by the name of COVID-19, but even if we weren’t social distancing, insects simply aren’t a concern at this time of year. So it’s little surprise that these months are often the best time to find a great deal on gadgets designed to deter or outright obliterate airborne insects.

Whatever PIC stands for…it’s not that.

Case in point, I was able to pick up this “Bug Zapper LED Bulb” at the big-box hardware store for just a few bucks. This one is sold by PIC Corporation, though some press release surfing shows the company merely took over distribution of the device in 2017. Before then it was known as the Zapplight, and was the sort of thing you might see advertised on TV if you were still awake at 3 AM. It appears there are several exceptionally similar products on the market as well, which are likely to be the same internally.

In all fairness, it’s a pretty clever idea. Traditional zappers are fairly large, and need to be hoisted up somewhere next to an electrical outlet. But if you could shrink one down to the size of a light bulb, you could easily dot them around the porch using the existing sockets and wiring. Extra points if you can also figure out a way to make it work as a real bulb when the bugs aren’t out. Obviously the resulting chimera won’t excel at either task, but there’s certainly something to be said for the convenience of it.

Let’s take a look inside one of these electrifying illuminators and see how they’ve managed to squeeze two very different devices into one socket-friendly package.

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Replacement LED Light Build Uses A Few Tricks

Microscopes have become essential work bench tools for hackers, allowing them to work with tiny SMD parts for PCB assembly and inspection. Couple of years back, mad scientist [smellsofbikes] picked up a stereo microscope from eBay. But its odd-sized, 12 volt Edison-style screw base lamp, connected to a 17 volt AC supply, burned off after a while. He swapped the burnt lamp with the spare, which too blew up after some time. Dumb lamps. Maybe the original spec called for 24 volt lamps, which were unobtanium due to the odd Edison screw base, but those would throw out a pretty yellow-orange glow. Anyhow, for some time, he worked with a jury-rigged goose neck lamp, but frequently moving the microscope and the lamp was becoming a chore. When he got fed up enough about it, he decided to Build a Replacement LED Microscope Light.

Usually, such builds are plain vanilla and not much to write in about, but [smellsofbikes] has a few tricks worth taking note of. He found a couple of high power, SMD LEDs in his parts bin. They were just slightly wider than 1.6 mm across the terminals. So he took a piece of double sided, copper clad FR4, and edge mounted the LED against one side of the PCB piece, twisting it slightly so he could solder both terminals. This works as a great heat sink for the LED while still having a very narrow profile. This was important as the replacement LED board had to fit the cylinder in which the original lamp was fitted.

The LED is driven by a constant current buck regulator, powered by the original 17 volt transformer. A bridge rectifier and several filter capacitors result in a low ripple DC supply, for which he used the KiCad spice functionality to work out the values. The LM3414 driver he used is a bit off the beaten track. It can run LEDs up to 60 watts at 1 amps and does not require an external current sense resistor. This was overkill since he planned to run the LED at just 150 mA, which would result in a very robust, long lasting solution. He designed the driver PCB in KiCad, and milled it on his LPKF circuit board plotter. The nice thing with CNC milled PCBs is that you can add custom copper floods and extend footprint pads. This trick lets you solder either a 0805 or a 1206 part to the same footprint – depending on what you can dig up from your parts bin.

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Fake That Fireplace Flicker With Flame Bulbs

Ask anyone who’s ever tuned into Fireplace TV on a cold winter’s night — even though you can’t feel the heat or roast a marshmallow with it, fake fire is almost as soothing as the real thing. And if you have kids or pets, it’s a whole lot safer. But why go to the expense of buying a lighted insert when you could just make your own?

You don’t even need to get fancy with a microcontroller and RGB LEDs, either — just do what [Ham-made] did and dismantle some LED flame bulbs. They already have everything you need, and the flex PCB makes them easy to work with.

[Ham-made] adhered three bulbs’ worth to a piece of foam board with double-stick tape, soldered all the leads together, and wired in a toggle switch and a 2xAA battery pack. The bulbs each had a tilt switch so that the “flames” flow upward regardless of orientation, but [Ham-made] removed those to avoid flickering connectivity and fights with the toggle switch.

Once it was all wired up, [Ham-made] hot-glued some magnets to the foam board and attached it to the underside of the grate to keep it safe from the logs and the ash pit, while still allowing the glow to emanate from the right spot for realism. The only thing missing are the crackles and pops, and [Ham-made] is burning to hear your implementation ideas.

[Ham-made] wasn’t using his fireplace in the traditional way because the house is smallish and centrally heated. But if you rely on yours to keep you warm and cozy, why not make it voice-activated?

2019: As The Hardware World Turns

Well, this is it. The end of the decade. In a few days the 2010s will be behind us, and a lot of very smug people will start making jokes on social media about how we’re back in the “Roaring 20s” again. Only this time around there’s a lot more plastic, and drastically less bathtub gin. It’s still unclear as to how much jazz will be involved.

Around this time we always say the same thing, but once again it bears repeating: it’s been a fantastic year for Hackaday. Of course, we had our usual honor of featuring literally thousands of incredible creations from the hacking and making community. But beyond that, we also bore witness to some fascinating tech trends, moments that could legitimately be called historic, and a fair number of blunders which won’t soon be forgotten. In fact, this year we’ve covered a wider breadth of topics than ever before, and judging by the record setting numbers we’ve seen in response, it seems you’ve been just as excited to read it as we were to write it.

To close out the year, let’s take a look at a few of the most popular and interesting stories of 2019. It’s been a wild ride, and we can’t wait to do it all over again in 2020.

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What Happened To The 100,000-Hour LED Bulbs?

Early adopters of LED lighting will remember 50,000 hour or even 100,000 hour lifetime ratings printed on the box. But during a recent trip to the hardware store the longest advertised lifetime I found was 25,000 hours. Others claimed only 7,500 or 15,000 hours. And yes, these are brand-name bulbs from Cree and GE.

So, what happened to those 100,000 hour residential LED bulbs? Were the initial estimates just over-optimistic? Was it all marketing hype? Or, did we not know enough about LED aging to predict the true useful life of a bulb?

I put these questions to the test. Join me after the break for some background on the light bulb cartel from the days of incandescent bulbs (not a joke, a cartel controlled the life of your bulbs), and for the destruction of some modern LED bulbs to see why the lifetimes are clocking in a lot lower than the original wave of LED replacements.

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