Hackaday Prize Entry: Characterizing LED and Laser Diodes

Needless to say, we’re fascinated by LEDs, laser diodes, and other blinkies. Although we can get just about any light emitting thing, the data sheets aren’t always accurate or available. For his Hackaday Prize entry, [Ted] is building a device to characterize the efficiency, I/V curve, and optical properties of all the blinkies. It’s a project to make glowy stuff better, and a great entry for the Hackaday Prize.

The inspiration for this project came from two of [Ted]’s projects, one requiring response curves for LEDs, and laser diodes for another. This would give him a graph of optical output vs. current, angular light output distribution, and the lasing threshold for laser diodes. This data isn’t always available in the datasheet, so a homebrew tool is the only option.

The high-level design of this tool is basically a voltmeter and ammeter measuring a glowy diode, producing IV curves and measuring optical output. That takes care of all the measurements except for the purely optical properties of a LED. This is measured by a goniometer, or basically putting the device under test on a carriage attached to a stepper motor and moving it past a fixed optical detector.

If you’re wondering why this device is needed and a simple datasheet is insufficient, check this out. [Ted] measured the efficiency of a Luxeon Z LED, and found the maximum efficiency is right around 10mA. The datasheet for this LED shows a nominal forward current of 500mA, and a maximum of 1000mA. If you just looked at the datasheet, you could easily assume a device powered for years by a coin cell would be impossible. It’s not, and [Ted]’s device gave us this information.

Water-Cooled LED Light

[Matt] wanted to drive a Yuji LED array. The LED requires 30 V and at 100 watts, it generates a lot of heat. He used a Corsair water cooling system made for a CPU cooler to carry away the heat. The parts list includes a microphone gooseneck, a boost converter, a buck converter (for the water cooler) and custom-made brackets (made from MDF). There’s also a lens and reflector that is made to go with the LED array.

This single LED probably doesn’t require water cooling. On the other hand, adding a fan would increase the bulk of the lighted part and the gooseneck along with the water cooling tubes looks pretty cool. This project is a good reminder that if you need to carry heat away from something with no fans, self-contained water cooling systems are fairly inexpensive now, thanks to the PC market.

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A Helmet to Make Daft Punk Jealous

If you’ve been paying even a little bit of attention to popular music over the past couple of decades, then you’re surely aware of the electronic music duo Daft Punk. Of course, their success isn’t just a result of their music – a big part of it is also their iconic costumes and persona. What makes those costumes iconic is the robot helmets that the musicians wear. What initially began as a desire to hide their faces ended up becoming their most distinctive trait.

The helmets that the duo wears have changed over the years, but an homage helmet created by [Mike Michelena] puts them all to shame. It maintains the aesthetic elements of Daft Punk’s helmets, while improving on the tech aspects in every way. 210 RGB LEDs, a microprocessor, and 14 amp hours worth of battery give it complete customizability and 5 hours of use.

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Rita’s Dolls Probably Live Better Than You Do

If it wasn’t for the weird Dutch-Norwegian techno you’d presumably have to listen to forever, [Gianni B.]’s doll house for his daughter, [Rita] makes living in a Barbie World seem like a worthwhile endeavor. True to modern form, it’s got LED lighting. It’s got IoT. It’s got an app and an elevator. It even has a tiny, working, miniature television.

It all started with a Christmas wish. [Rita] could no longer stand to bear the thought of her Barbie dolls living a homeless lifestyle on her floor, begging passing toys for enough monopoly money to buy a sock to sleep under. However, when [Gianni] visited the usual suspects to purchase a dollhouse he found them disappointing and expensive.

So, going with the traditional collaborating-with-Santa ruse, he and his family had the pleasure of collaborating on a dollhouse development project. Each room is lit by four ultra bright LEDs. There is an elevator that’s controlled by an H-bridge module, modified to have electronic braking. [Rita] doesn’t own a Dr. Barbie yet, so safety is paramount.

The brain of the home automation is a PIC micro with a Bluetooth module. He wrote some code for it, available here. He also went an extra step and used MIT’s scratch to make an app interface for the dollhouse. You can see it work in the video after the break. The last little hack was the TV. An old arduino, an SD Card shield, and a tiny 2.4 inch TFT combine to make what’s essentially a tiny digital picture frame.

His daughter’s are overjoyed with the elevation of their doll’s economic class and a proud father even got to show it off at a Maker Faire. Very nice!

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Quick Hack Creates A Visual Beep Alarm

Sometimes a simple modification is all it takes to get something just the way you want it. The Ikea LÖTTORP clock/thermometer/timer caught [Mansour Behabadi’s] eye. The LÖTTORP  has four functions based on its orientation. [Mansour] loved the orientation feature, but hated the clock’s shrill beeping alert. Visual beeps or alarms can be handy when working with headphones or in a loud environment. With this in mind [Mansour] decided to crack his LÖTTORP open and rewire it to produce a visual beep for the timer function.

The clock is backlit, so [Behabadi] decided to use the backlight for his visual beep. Once the inside was exposed, [Behabadi] noticed that the buzzer’s positive terminal was wired to the red LED anode — a clever design choice, since the red LED is only used with the clock function. Simply removing the buzzer and soldering its terminal to the noticeable green LED provided the desired effect.

We meant it when we said he cracked it open. The screws were hidden behind the front plate, so the handyman’s secret weapon helped in reassembling the clock after this quick hack.

We’ve featured plenty of classy, unique, and ingenious clocks on Hackaday, so this modification is in good company.

Hackaday Prize Entry: Cheap Visible Light Communication

[Jovan] is very excited about the possibilities presented by Visible Light Communication, or VLC. It’s exciting and new. His opening paragraphs is filled with so many networking acronyms that VLC could be used for, our browser search history now looks like we’re trying to learn english without any vowels.

In lots of ways he has good reason to be excited. We all know that IR can communicate quite a bit, but when you’re clever about frequency and color and throw in some polarizers with a mix of clever algorithms for good measure you can get some very high bandwidth communication with anything in line of site. You can do it for low power, and best of all, there are no pesky regulations to stand in your way.

He wants to build a system that could be used for a PAN (Personal Area Network). To do this he’ll have to figure out a way to build the system inexpensively and using less than a watt of power. The project page is full of interesting experiments and quite a few thesis on the subject of LEDs.

For example, he’s done work on how LEDs respond to polarization. He’s tested how fast an LED can actually turn on and off while still being able to detect the change. He’s also done a lot of work characterizing the kind of light that an LED emits. We don’t know if he’ll succeed yet, but we like the interesting work he’s doing to get there.

Altitude Controlled LED Jacket Changes Color as You Climb

When your climbing gym throws a “glow in the dark” party, how can you stand out? For [Martijn], the answer was obvious. He made a jacket adorned with 32 WS2812 addressable LEDs whose color is addressable depending on the altitude to which he has climbed.
The build is centered on an Arduino Pro Mini with a barometric sensor and an NRF24L01 for radio comms. A pair of pockets contain AA batteries for power, and he’s all set to climb.
A base station Arduino with the same set-up transmits an up-to-the-minute reading for ground level temperature, which is compared to the local reading from the barometric sensor and used to calculate a new color for the LEDs. A Kalman filter deals with noise on the pressure reading to assure a stable result. Arduino sketches for both ends are provided on the Hackaday.io page linked above.
The LEDs are mounted on the jacket’s stretch fabric with an excess of  wire behind the scenes to cater for the stretch. You can see the resulting garment in the short YouTube video below the break.

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