FoTW: LED Strips Make Awful Servo Drivers

We must all have at some time or another spotted a hack that seems like an incredible idea and which just has to be tried, but turns out to have been stretching the bounds of what is possible just a little too far. A chunk of our time has disappeared without trace, and we sheepishly end up buying the proper part for the job in hand.

[Orionrobots] had a conversation with a YouTube follower about LED strips. An LED strip contains a length of ready-made PWM drivers, they mused. Wouldn’t it be great then, if each of the drivers on a strip could be connected to a servo, making the strip a ready-made single-stop SPI servo driver. With a large multi-servo robot to build, he set to work on a strip of WS2801s.

If you are in the Soldering Zone and have elite skills at the iron, then soldering a wire to a surface mount driver chip is something entirely possible. For mere mortals though it’s a bit of a challenge, and he notes just how much extra time it’s added to the project. The fun starts though when the servo is hooked up, the best that can be said is that it vibrates a bit. On paper, the LED drivers should be able to drive a servo, because they can create the correct waveform. But in practice the servo is designed to accept a logic level input while the driver is designed to sit in series with an LED and control its current. In practice therefore the voltages required for a logic transition can’t quite be achieved.

He concludes by recommending that viewers splash out on a servo driver board rather than trying an LED strip. We applaud him for the effort, after all it’s a hack any of us might have thought of trying for ourselves.

Continue reading “FoTW: LED Strips Make Awful Servo Drivers”

Dollar Tree LED Bulb Tear Down

It is hard to remember now, but there was a time when electronics were expensive. [Adrian Black] found some 9W (60W equivalent) LED light bulbs at the Dollar Tree (a U.S. store where everything costs a dollar). Naturally, they cost a dollar, and he wanted to see what was inside of them. You can see the resulting video, below.

Apparently where [Adrian] lives there is a subsidy paid to retailers for selling LED lighting, so you may not be able to get the same bulbs at that price. Still, the price of these bulbs has dropped like a rock over the last few years.

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The Art of Blinky Business Cards

Business cards are stuck somewhere between antiquity and convenience. On one hand, we have very convenient paperless solutions for contact swapping including Bluetooth, NFC, and just saying, “Hey, put your number into my phone, please.” On the other hand, holding something from another person is a more personal and memorable exchange. I would liken this to the difference between an eBook and a paperback. One is supremely convenient while the other is tactile. There’s a reason business cards have survived longer than the Rolodex.

Protocols and culture surrounding the exchange of cards are meant to make yourself memorable and a card which is easy to associate with you can work long after you’ve given your card away. This may seem moot if you are assigned cards when you start a new job, but personal business cards are invaluable for meeting people outside of work and you are the one to decide how wild or creative to make them.

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World’s Largest Telescope Stopped by LED

Earlier this year a simple indicator LED brought the Keck 1 telescope, a 370 tons mass, to a halting stop. How exactly did an LED do this? Simple: it did nothing.

As it so happens, [Andrew Cooper] was just about the leave the summit of Mauna Kea (in Hawaii) when his radio instructed him otherwise: there was an issue. Upon returning, [Andrew] was met by a room of scientists and summit supervisors. “Yeah, this was not good, why are they all looking at me? Oh, h%#*!” The rotor wasn’t moving the telescope, and “no rotator equals no science data.” After being briefed on the problem, [Andrew] got to work. Was it a mechanical issue? No: manual mode worked quite fine, also indicating that the amplifiers and limit switches are functional as well.

Jumping from chip to chip, [Andrew] came across an odd voltage: 9.36V. In the CMOS [Andrew] was investigating, this voltage should have High (15V) or Low (0v) and nowhere in between. Judging by the 9.36V [Andrew] decided to replace the driving IC. One DS3632 later, nothing had changed. Well, maybe is one of the loads pulling the line low? With only two choices, [Andrew] eliminated that possibility quickly. Likely feeling as if he was running out of proverbial rope, [Andrew] remembered something important: “the DS3236 driving this circuit is an open collector output, it needs a pull-up to go high.”

Reviewing the schematic, [Andrew] identified the DS3236’s pull-up: an LED and its current limiting resistor. While the carbon composition resistor was “armageddon proof,” [Andrew] was suspicious of the LED. “Nick, can you get me a 5k resistor from the lab?” Hold the resistor on the pins of the chip and the amplifiers immediately enabled.

[Andrew] summarizes things quite well: “yes… One of the world’s largest telescopes, 370 tons of steel and glass, was brought to a halt because of a bad indicator LED”. It stopped things by doing nothing, or rather, by not turning on.

We love it when we get troubleshooting stories, and if you share our interest in problem-solving, check out this broken power supply troubleshooting or learn what could go wrong with I2C.

Edit: Keck 1 is one of the largest optical telescopes in the world. Thanks to [Josh] for noticing our error.

FM Snake Feeds Off Radio Waves

[Eric Brasseur] built a radio-detecting snake that consists of a LED that lights up when around reasonably strong radio waves. Near an FM radio mast you’ll find a huge amount of waste energy being dumped out in the 88 to 108 MHz range.

[Eric]’s rig consists of a pair of 1N6263 Schottky diodes, flip-flopped with one set of ends soldered to the antenna and the other ends soldered to the leads of the LED with about a foot of wire in between. The antenna can be a single wire as the diodes are soldered together. This one is around 4 feet in length for a total length of around 160 cm or a little over 5 feet. He went with a red LED just to give it a greater chance of being seen when illuminated by a distant or weak source of radio waves.

Hackaday loves its radio hacks; check out our posts on improving WiFi throughput with FM radio and building a modern DIY FM radio.

[Thanks, Alain!]

Friday Hack Chat: All About LED Design

There are three great enabling technologies of the last twenty years. The first is lithium batteries that hold a lot of juice. Quadcopters wouldn’t exist without them, and the Tesla Model S wouldn’t either. The second is crazy powerful brushless motors. Here, again, quads wouldn’t exist without them, but we’re also getting smaller, torquier, and more powerful motion platforms.

The third great enabling technology in recent memory is LEDs. Remember when the PlayStation 2 came out, and everyone was amazed by the blue LED? That blue LED won a Nobel Prize. Now, we have LED light bulbs, LEDs in any color of the rainbow, powerful UV LEDs, and bazillion candela flashlights. LEDs are awesome.

For this week’s Hack Chat, we’re going to be talking all about LEDs. Everything from strips to rings, discrete to waterproof, COBs, weird colors, and everything in between. If you’re looking to replace your workshop lighting with LEDs, this is the Hack Chat for you. If you’ve ever wondered about the quality of LEDs, and the price-performance ratio, this is for you. This is all about blinky bling.

Our guest for this week’s Hack Chat will be [Metalnat], founder of the Burbank MakerSpace, a recent resident of the Supplyframe DesignLab where he designed a VR controller, and worked on Crane, a flapping automaton that glided over the playa at this year’s Burning Man. During this Hack Chat, we’ll be talking about LEDs, including installation methods, types of LEDs, suppliers, and LED manufacturing methods.

This is a Hack Chat, so we’re taking questions from the audience. Here’s a spreadsheet we’ll be using to guide the discussion.

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hack Chat group messaging. This Hack Chat will be going down noon, Pacific time on Friday, September 29th. Sidereal and solar getting you down? Wondering when noon is this month? Not a problem: here’s a handy countdown timer!

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

Need a Night-Light?

[Scott] created an LED candle in preparation for the big mac daddy storm (storms?) coming through.  Like millions of other people in Florida, he was stuck at home with his roommates when an oncoming hurricane headed their way.  Worrying about blundering about in the dark when the power inevitably went out, they set off to gather up all of the candles they had lying around.  Realizing the monstrous pile of candles and matches looked more and more like a death wish, the decision was made to create a makeshift light out of what components they had on hand.  Now, not having access to any outside sources for parts means that you are going to have a bare bones model.

That being said, this straightforward light only takes a couple of seconds to put together.  Jury rig a couple of AA or AAA batteries up, then slap on a resistor, LED, and jumper to get that sucker running.  Wrap electrical tape around the whole thing, or even try duct tape, whatever gets the job done.  A little paper hat on top of it will diffuse the light and bada bing, bada boom, you’re all done.  Generally though, soldering directly onto a battery is not a wise idea.  So, if you want to get fancy, perhaps a better alternative is to have a battery casing as shown below.

This LED candle is a clear option if your home isn’t a micro warehouse for electronic components (apparently it is frowned upon to clog up your garage for projects), and you have limited time.  However, if you have a number of extra minutes lying around before your windows blow in, see if you can top the brightest flashlight ever made (thus far).  Continue reading “Need a Night-Light?”