New Power Factor-Corrected AC-DC Drivers for LED Lighting Apps

ON Semiconductor has announced two new series of power factor corrected (PFC) offline AC-DC drivers for high performance LED lighting applications. Extending the NCL3008x family of products, the NCL30085, NCL30086, and NCL30088 address single-stage design implementations up to 60 W that require high power factor. The NCL30030 broadens the existing solutions which support higher power (up to 150 W) two-stage topologies that require low optical ripple and wide LED forward voltage variation.

 

Source: ON Semiconductor

Source: ON Semiconductor

The NCL30085, NCL30086, and NCL30088 use a PFC current control algorithm that makes them suitable for flyback buck-boost and SEPIC topologies. By operating in quasi-resonant mode, they can deliver optimum efficiency across wide line and load levels. The innovative control methodology enables strict current regulation to be achieved (within 2% typically) solely from the primary side.

 

The non-dimmable NCL30088 is complemented by the “smart-dimmable” NCL30086, supporting analog and pulse-width modulation (PWM) dimming with a single input that controls the average LED current. Completing the series is the NCL30085, which supports three levels of log step dimming: 70%, 25%, and 5%. As a result, it permits light output reduction by toggling the AC switch on/off to signal the controller to lower the LED current point. All three devices feature user-configurable current thermal fold-back mechanisms that help prevent overheating and enable manufacturers to support longer lifetime warranties.

 

The NCL30085 and NCL30088 are available in SOIC-8 packages. The NCL30086 is offered in an SOIC-10 package with pricing of the series starting at $0.35 per unit in 10,000-piece quantities.

 

The NCL30030 is a two-stage PFC controller plus quasi-resonant flyback controller optimized for medium and high power LED lighting applications up to 150 W. This device is best suited for commercial lighting such as lowbay, highbay, and streetlighting. The NCL30030 makes use of a proprietary multiplier architecture to achieve low harmonic distortion and near-unity power factor while operating in critical conduction mode (CrM).

The NCL30030 is in an SOIC−16 package with one pin removed for high-voltage spacing. Pricing starts at $0.65 per unit in 10,000-piece quantities.

 

Source: ON Semiconductor

LED Light Engines Deliver Up to 4,000 Lumens

Innovations in Optics has announced  high-power white LED light engines for OEM fiberoptic illumination. LumiBright Light Engines couple directly to liquid light guides and fiber bundles with no additional optics. They deliver up to 4,000 lumens into the light guide.

The 2400-W (Source:

The 2400-W (Source: Innovations in Optics)

Offering substantial cost and operational advantages, white LEDs are becoming popular light guide illumination sources for many technical applications that were historically dominated by tungsten halogen and HID lamps. LumiBright light engines feature patented technologies that encompass non-imaging optics with chip-on-board (COB) LED arrays on metal core circuit boards to provide both optimum luminous efficacy and ideal thermal management. Unlike the so called “big chip” LEDs used in many light guide illuminators, LumiBright light engines feature large source size and emit into a numerical aperture that matches the acceptance cone angle and diameter of light guide systems. The unique design results in many more lumens emitted from light guides relative to the big chip Lambertian emitters.

The LumiBright 2400B-400-W has a 0.66 numerical aperture (NA) and illuminates fiber bundles and light guides sized from 6.0 to 8.0 mm in diameter. Well suited for applications in machine vision and remote source illumination, the light engine generates up to 4,000 lumens. The 2400B-500-W is ideally suited for endoscope and microscope illuminator applications with a 0.60 NA for light guides that are 3.0 to 5.0 mm in diameter. The 2400B-500-W produces up to 1,500 lumens. Available light engine system accessories include thermal management devices, wire harnesses, and driver/controllers.

Source: Innovations in Optics

Data Communication Between “Smart” Pendants

As head of the Computer Science and Software  Engineering department at Penn State Erie, The Behrend College, Chris Coulston is busy.

But not too busy to surf the ‘Net for design inspiration.

And one of his latest projects may earn him the title of “social jewelry designer,” along with college professor and department chair.

In the June issue of Circuit Cellar, Coulston writes about his design and construction of an RGB LED pendant that “cycles through a color sequence, detects when another pendant is brought into its proximity, and communicates color sequence information to the other pendant through its LED.” The heart of the design is a Seoul Semiconductor SFT722 RGB LED.

Coulston was online a few years ago when he ran across the first half of his project inspiration—a Mitsubishi Electric Research Laboratories technical report titled “Very Low-Cost Sensing and Communication Using Bi-directional LEDs.” The report, Coulston says, “describes how an ordinary LED with no additional circuitry can act as a full-duplex communication channel.”

Pendant’s two boards

His remaining inspiration came from an article he recalled appearing in Circuit Cellar a decade ago.

The Mitsubishi labs technical report “got me thinking about Jeff Bachiochi’s article ‘Designing with RGB LEDs’ (Circuit Cellar 159, 2003), in which the challenges associated with designing a piece of LED jewelry are described,” Coulston says. “The fusion of these two ideas was the inspiration for my social jewelry design.”

Coulston’s design includes a pair of circuit boards, the upper containing the LED and analog circuitry and the lower containing the microcontroller.

“The prototype pendant is mainly controlled through a USB-to-USART bridge,” Couston says. “Its power is supplied by the same connection.”

He invites anyone who is  “curious how an LED can be used as a transceiver and how it’s used to build a piece of social jewelry” to read his article. You’ll find it in next month’s issue of Circuit Cellar.

Q&A: Raspberry Pi Innovation

Orlando, FL-based web app developer and blogger Shea Silverman recently received Kickstarter funding for the latest version of PiPlay, his Raspberry Pi-based OS. Shea and I discussed his ongoing projects, his Raspberry Pi book, and what’s next for PiPlay.—Nan Price, Associate Editor

 

silverman

Shea Silverman

NAN: What is your current occupation?

SHEA: Web applications developer with the Center for Distributed Learning at the University of Central Florida (UCF).

NAN: Why and when did you decide to start your blog?

SHEA: I’ve been blogging on and off for years, but I could never keep to a schedule or really commit myself to writing. After I started working on side projects, I realized I needed a place to store tips and tricks I had figured out. I installed WordPress, posted some PhoneGap tips, and within a day got a comment from someone who had the same issue, and my tips helped them out. I have been blogging ever since. I make sure to post every Friday night.

NAN: Tell us about PiPlay, the Raspberry Pi OS. Why did you start the OS? What new developments, if any, are you working on?

piplay-case

Shea’s PiPlay Raspberry Pi OS recently reached 400% funding on Kickstarter.

SHEA: PiPlay is a gaming and emulation distribution for the Raspberry Pi single-board computer. It is built on top of the Raspbian OS, and tries to make it as easy as possible to play games on your Raspberry Pi. My blog got really popular after I started posting binaries and tutorials on how to compile different emulators to the Raspberry Pi, but I kept getting asked the same questions and saw users struggling with the same consistent issues.

I decided I would release a disk image with everything preconfigured and ready to be loaded onto an SD card. I’ve been adding new emulators, games, and tools to it ever since.

I just recently completed a Kickstarter that is funding the next release, which includes a much nicer front end, a web GUI, and a better controller configuration system.

NAN: You wrote Instant Raspberry Pi Gaming. Do you consider this book introductory or is it written for the more experienced engineer?

SHEA: Instant Raspberry Pi Gaming is written like a cookbook with recipes for doing various tasks. Some of them are very simple, and they build up to some more advanced recipes. One of the easier tasks is creating your user account on the Pi Store, while the more advanced recipes have you working with Python and using an API to interact with Minecraft.

Readers will learn how to setup a Raspberry Pi, install and use various emulators and games, a bit about the Minecraft API, and common troubleshooting tips.

pitroller

The Pitroller is a joystick and buttons hooked up to the GPIO pins of a Raspberry Pi, which can act as a controller or keyboard for various emulators.

NAN: You are a member of FamiLAB, an Orlando, FL-based community lab/hackerspace. What types of projects have you worked on at the lab?

miniarcade

Disney director Rich Moore poses with Shea’s miniature arcade machine. The machine was based on Fix It Felix Jr. from Disney’s Wreck It Ralph.

SHEA: I spend a lot of time at the lab using the laser cutter. Creating a 2-D vector in Inkscape, and then watching it be cut out on a piece of wood or acrylic is really inspiring. My favorite project was making a little arcade machine featuring Fix It Felix Jr. from Wreck It Ralph. A marketing person from Disney was able to get it into the hands of the director Rich Moore. He sent me a bunch of pictures of himself holding my little arcade machine next to the full size version.

NAN: Give us a little background information. How did you become interested in technology?

SHEA: My mom always likes to remind me that I’ve been using computers since I was 2. My parents were very interested in technology and encouraged my curiosity when it came to computers. I always liked to take something apart and see how it worked, and then try to put it back together. As the years went on, I’ve devoted more and more time to making technology a major part of my life.

NAN: Tell us about the first embedded system you designed.

SHEA: I have a lot of designs, but I don’t think I’ve ever finished one. I’ll be halfway into a project, learn about something new, then cannibalize what I was working on and repurpose it for my new idea. One of the first embedded projects I worked on was a paintball board made out of a PICAXE microcontroller. I never got it small enough to fit inside the paintball marker, but it was really cool to see everything in action. The best part was when I finally had that “ah-ha!” moment, and everything I was learning finally clicked.

NAN: What was the last electronics-design related product you purchased and what type of project did you use it with?

SHEA: At UCF, one of our teams utilizes a ticket system for dealing with requests. Our department does a hack day each semester, so my coworker and I decided to rig up a system that changes the color of the lights in the office depending on the urgency of requests in the box. We coded up an API and had a Raspberry Pi ping the API every few minutes for updates. We then hooked up two Arduinos to the Raspberry Pi and color-changing LED strips to the Arduinos. We set it up and it’s been working for the past year and a half, alerting the team with different colors when there is work to do.

NAN: Are you currently working on or planning any projects?

SHEA: My Kickstarter for PiPlay just finished at 400% funding. So right now I’m busy working on fulfilling the rewards, and writing the latest version of PiPlay.

NAN: What do you consider to be the “next big thing” in the industry?

SHEA: Wearable computing. Google Glass, the Pebble smart watch, Galaxy Gear—I think these are all great indicators of where our technology is heading. We currently have very powerful computers in our pockets with all kinds of sensors and gadgets built in, but very limited ways to physically interact with them (via the screen, or a keypad). If we can make the input devices modular, be it your watch, a heads-up display, or something else, I think that is going to spark a new revolution in user experiences.

Battery Charger Design (EE Tip #130)

It’s easy to design a good, inexpensive charger. There is no justification for selling cheap, inadequate contraptions. Many companies (e.g., Linear Technology, Maxim, Semtech, and Texas Instruments) supply inexpensive battery management ICs. With a few external parts, you can build a perfect charger for just about any battery.

Texas Instruments’s UC2906 is an older (Unitrode) IC designed to build an excellent sealed lead-acid battery charger with a sophisticated charging profile. Figure 1 shows the recommended charger circuit.

Figure 1: This lead-acid battery charger uses Texas Instruments’s UC2906 IC.

Figure 1: This lead-acid battery charger uses Texas Instruments’s UC2906 IC.

In addition to the IC, only a handful of resistors and a PNP power transistor Q1 are needed to build it. Q1 must be rated for the maximum charging current and fitted with a heatsink.

An LED with its current-limiting resistor R can be connected to pin 7, which is an open-collector NPN transistor, to indicate the presence of power. Similarly, an LED with a series resistor could be connected to pin 9, which is also an open-collector NPN transistor to indicate overcharge (it is not used in Figure 1). The UC2906 datasheet and the Application Note provide tables and equations for selection of resistors Rs, Rt, RA, RB, RC, and RD and suggestions for adding various features.

Editor’s Note: This is an excerpt from an article written by George Novacek, “Battery Basics (Part 3): Battery Management ICs,” Circuit Cellar 280, 2013.

The Future of Monolithically Integrated LED Arrays

LEDs are ubiquitous in our electronic lives. They are widely used in notification lighting, flash photography, and light bulbs, to name a few. For displays, LEDs have been commercialized as backlights in televisions and projectors. However, their use in image formation has been limited.

A prototype emissive LED display chip is shown. The chip includes an emissive compass pattern ready to embed into new applications.

A prototype emissive LED display chip is shown. The chip includes an emissive compass pattern ready to embed into new applications.

The developing arena of monolithically integrated LED arrays, which involves fabricating millions of LEDs with corresponding transistors on a single chip, provides many new applications not possible with current technologies, as the LEDs can simultaneously act as the backlight and the image source.

The common method of creating images is to first generate light (using LEDs) and then filter that light using a spatial light modulator. The filter could be an LCD, liquid crystal on silicon (LCoS), or a digital micromirror device (DMD) such as a Digital Light Processing (DLP) projector. The filtering processes cause significant loss of light in these systems, despite the brightness available from LEDs. For example, a typical LCD uses only 1% to 5% of the light generated.

Two pieces are essential to a display: a light source and a light controller. In most display technologies, the light source and light control functionalities are served by two separate components (e.g., an LED backlight and an LCD). However, in emissive displays, both functionalities are combined into a single component, enabling light to be directly controlled without the inherent inefficiencies and losses associated with filtering. Because each light-emitting pixel is individually controlled, light can be generated and emitted exactly where and when needed.

Emissive displays have been developed in all sizes. Very-large-format “Times Square” and stadium displays are powered by large arrays of individual conventional LEDs, while new organic LED (OLED) materials are found in televisions, mobile phones, and other micro-size applications. However, there is still a void. Emissive “Times Square” displays cannot be scaled to small sizes and emissive OLEDs do not have the brightness available for outdoor environments and newer envisioned applications. An emissive display with high brightness but in a micro format is required for applications such as embedded cell phone projectors or displays on see-through glasses.

We know that optimization by the entire LED industry has made LEDs the brightest controllable light source available. We also know that a display requires a light source and a method of controlling the light. So, why not make an array of LEDs and control individual LEDs with a matching array of transistors?

The marrying of LED materials (light source) to transistors (light control) has long been researched. There are three approaches to this problem: fabricate the LEDs and transistors separately, then bond them together; fabricate transistors first, then integrate LEDs on top; and fabricate LEDs first, then integrate transistors on top. The first method is not monolithic. Two fabricated chips are electrically and mechanically bonded, limiting integration density and thus final display resolutions. The second method, starting with transistors and then growing LEDs, offers some advantages in monolithic (single-wafer) processing, but growth of high-quality, high-efficiency LEDs on transistors has proven difficult.

My start-up company, Lumiode (www.lumiode.com), is developing the third method, starting with optimized LEDs and then fabricating silicon transistors on top. This leverages existing LED materials for efficient light output. It also requires careful fabrication of the integrated transistor layer as to not damage the underlying LED structures. The core technology uses a laser method to provide extremely local high temperatures to the silicon while preventing thermal damage to the LED. This overcomes typical process incompatibilities, which have previously held back development of monolithically integrated LED arrays. In the end, there is an array of LEDs (light source) and corresponding transistors to control each individual LED (light control), which can reach the brightness and density requirements of future microdisplays.

Regardless of the specific integration method employed, a monolithically integrated LED and transistor structure creates a new range of applications requiring higher efficiency and brightness. The brightness available from integrated LED arrays can enable projection on truly see-through glass, even in outdoor daylight environments. The efficiency of an emissive display enables extended battery lifetimes and device portability. Perhaps we can soon achieve the types of displays dreamed up in movies.

Traveling With a “Portable Workspace”

As a freelance engineer, Raul Alvarez spends a lot of time on the go. He says the last four or five years he has been traveling due to work and family reasons, therefore he never stays in one place long enough to set up a proper workspace. “Whenever I need to move again, I just pack whatever I can: boards, modules, components, cables, and so forth, and then I’m good to go,” he explains.

Raul_Alvarez_Workspace _Photo_1

Alvarez sits at his “current” workstation.

He continued by saying:

In my case, there’s not much of a workspace to show because my workspace is whichever desk I have at hand in a given location. My tools are all the tools that I can fit into my traveling backpack, along with my software tools that are installed in my laptop.

Because in my personal projects I mostly work with microcontroller boards, modular components, and firmware, until now I think it didn’t bother me not having more fancy (and useful) tools such as a bench oscilloscope, a logic analyzer, or a spectrum analyzer. I just try to work with whatever I have at hand because, well, I don’t have much choice.

Given my circumstances, probably the most useful tools I have for debugging embedded hardware and firmware are a good-old UART port, a multimeter, and a bunch of LEDs. For the UART interface I use a Future Technology Devices International FT232-based UART-to-USB interface board and Tera Term serial terminal software.

Currently, I’m working mostly with Microchip Technology PIC and ARM microcontrollers. So for my PIC projects my tiny Microchip Technology PICkit 3 Programmer/Debugger usually saves the day.

Regarding ARM, I generally use some of the new low-cost ARM development boards that include programming/debugging interfaces. I carry an LPC1769 LPCXpresso board, an mbed board, three STMicroelectronics Discovery boards (Cortex-M0, Cortex-M3, and Cortex-M4), my STMicroelectronics STM32 Primer2, three Texas Instruments LaunchPads (the MSP430, the Piccolo, and the Stellaris), and the following Linux boards: two BeagleBoard.org BeagleBones (the gray one and a BeagleBone Black), a Cubieboard, an Odroid-X2, and a Raspberry Pi Model B.

Additionally, I always carry an Arduino UNO, a Digilent chipKIT Max 32 Arduino-compatible board (which I mostly use with MPLAB X IDE and “regular” C language), and a self-made Parallax Propeller microcontroller board. I also have a Wi-Fi 3G TP-LINK TL-WR703N mini router flashed   with OpenWRT that enables me to experiment with Wi-Fi and Ethernet and to tinker with their embedded Linux environment. It also provides me Internet access with the use of a 3G modem.

Raul_Alvarez_Workspace _Photo_2

Not a bad set up for someone on the go. Alvarez’s “portable workstation” includes ICs, resistors, and capacitors, among other things. He says his most useful tools are a UART port, a multimeter, and some LEDs.

In three or four small boxes I carry a lot of sensors, modules, ICs, resistors, capacitors, crystals, jumper cables, breadboard strips, and some DC-DC converter/regulator boards for supplying power to my circuits. I also carry a small video camera for shooting my video tutorials, which I publish from time to time at my website (www.raulalvarez.net). I have installed in my laptop TechSmith’s Camtasia for screen capture and Sony Vegas for editing the final video and audio.

Some IDEs that I have currently installed in my laptop are: LPCXpresso, Texas Instruments’s Code Composer Studio, IAR EW for Renesas RL78 and 8051, Ride7, Keil uVision for ARM, MPLAB X, and the Arduino IDE, among others. For PC coding I have installed Eclipse, MS Visual Studio, GNAT Programming Studio (I like to tinker with Ada from time to time), QT Creator, Python IDLE, MATLAB, and Octave. For schematics and PCB design I mostly use CadSoft’s EAGLE, ExpressPCB, DesignSpark PCB, and sometimes KiCad.

Traveling with my portable rig isn’t particularly pleasant for me. I always get delayed at security and customs checkpoints in airports. I get questioned a lot especially about my circuit boards and prototypes and I almost always have to buy a new set of screwdrivers after arriving at my destination. Luckily for me, my nomad lifestyle is about to come to an end soon and finally I will be able to settle down in my hometown in Cochabamba, Bolivia. The first two things I’m planning to do are to buy a really big workbench and a decent digital oscilloscope.

Alvarez’s article “The Home Energy Gateway: Remotely Control and Monitor Household Devices” appeared in Circuit Cellar’s February issue. For more information about Alvarez, visit his website or follow him on Twitter @RaulAlvarezT.

An Engineer Who Retires to the Garage

Jerry Brown, of Camarillo, CA, retired from the aerospace industry five years ago but continues to consult and work on numerous projects at home. For example, he plans to submit an article to Circuit Cellar about a Microchip Technology PIC-based computer display component (CDC) he designed and built for a traffic-monitoring system developed by a colleague.

Jerry Brown sits at his workbench. The black box atop the workbench is an embedded controller and is part of a traffic monitoring system he has been working on.

Jerry Brown sits at his workbench. The black box atop the workbench is an embedded controller and part of  his traffic monitoring system project.

“The traffic monitoring system is composed of a beam emitter component (BEC), a beam sensor component (BSC), and the CDC, and is intended for unmanned use on city streets, boulevards, and roadways to monitor and record the accumulative count, direction of travel, speed, and time of day for vehicles that pass by a specific location during a set time period,” he says.

Brown particularly enjoys working with PWM LED controllers. Circuit Cellar editors look forward to seeing his project article. In the meantime, he sent us the following description and pictures of the space where he conceives and executes his creative engineering ideas.

Jerry's garage-based lab.

Brown’s garage-based lab.

My workspace, which I call my “lab,” is on one side of my two-car garage and is fairly well equipped. (If you think it looks a bit messy, you should have seen it before I straightened it up for the “photo shoot.”)  

I have a good supply of passive and active electronic components, which are catalogued and, along with other parts and supplies, are stored in the cabinets and shelves alongside and above the workbench. I use the computer to write and compile software programs and to program PIC flash microcontrollers.  

The photos show the workbench and some of the instrumentation I have in the lab, including a waveform generator, a digital storage oscilloscope, a digital multimeter, a couple of power supplies, and a soldering station.  

The black box visible on top of the workbench is an embedded controller and is part of the traffic monitoring system that I have been working on.

Instruments in Jerry's lab include a waveform generator, a digital storage oscilloscope, a digital multimeter, a couple of power supplies, and a soldering station.

Instruments in Brown’s lab include a waveform generator, a digital storage oscilloscope, a digital multimeter, a couple of power supplies, and a soldering station. 

Brown has a BS in Electrical Engineering and a BS in Business Administration from California Polytechnic State University in San Luis Obispo, CA. He worked in the aerospace industry for 30 years and retired as the Principal Engineer/Manager of a Los Angeles-area aerospace company’s electrical and software design group.

High-Tech Halloween

Still contemplating Halloween ideas? Do you have a costume yet? Is your house trick-or-treat ready? Perhaps some of these high-tech costumes and decorations will help get you in the spirit.

Recent Circuit Cellar interviewee Jeremy Blum designed a creative and high-tech costume that includes 12 individually addressable LEDs, an Adafruit microcontroller, and 3-D printing.

Skull_Side_Full_IMG_0067

Custom animatronic skull

RavenSide2Armature_IMG_0015

Animatronic talking raven

Looking for Halloween decoration inspiration? Peter Montgomery designed some programmable servo animation controllers built around a Freescale Semiconductor 68HC11 microcontroller and a Parallax SX28 configurable controller.

Peter’s Windows-based plastic skull is animated with RC servos controlled via a custom system. It moves at 24 or 30 frames per second over a custom RS-485 network.
This animatronic talking raven features a machined aluminum armature and moves via RC servos. The servos are controlled by a custom system using Windows and embedded controllers.

Peter’s Halloween projects were originally featured in “Servo Animation Controller” (Circuit Cellar 188, 2006). He displays the Halloween projects every year.

Feeling inspired? Share your tech-based Halloween projects with us.

New Product: LED Drivers for Dimmable Bulbs

The iW3606 and the iW3608 are single-stage, solid-state lighting (SSL) LED drivers. The iW3606 (8-W output power) and the iW3608 (15-W output power) feature configurable over-temperature protection (OTP) and derating functionality to provide predictability and reliability of bulb operating life.

Designed for all retrofit bulbs, including candle and GU10 lamp replacements used in existing phase-cut dimmer installations, the LED drivers manage poor dimming performance (e.g., pop-on, popcorning, dead travel, drop-out, and flicker) and short bulb lifetime or failure. Both drivers meet or exceed global regulations for power quality and efficiency with less than 0.92 power factor (PF) and less than 20% total harmonic distortion (THD).

The LED drivers’ OTP and derating feature addresses the thermal issues caused by the high and unpredictable operating temperatures in dimmable SSL applications. iWatt’s OTP derating monitors the temperature inside sealed SSL bulbs. When thermal conditions reach a point set by the system designer, the LED drivers automatically reduce the current drive to the LEDs, lowering the power dissipation and resulting in a cooler overall operation.

The iW3606 and the iW3608 feature a wide, flicker-free dimming range from 100% to 1% of measured light to closely match incandescent bulbs’ dimming performance. This enables smooth “natural” dimming with no light drop-out at the low end of the dimming range and virtually no dead travel where the light turns off before the dimmer control reaches the bottom of its travel.

The LED drivers’ low internal power consumption enables them to start at less than 5% of light output, which is a very low dimming level. This virtually eliminates pop-on, in which the light does not turn on at low dimmer levels and, as the dimmer level is raised, the light suddenly turns on. The low power consumption also helps eliminate popcorning effects, in which various bulbs in multiple-light installations on the same dimmer circuit can turn on at different dimmer-setting thresholds.

The iW3606 costs $0.46 and the iW3608 costs $0.51, both in 1,000-unit quantities.

 

iWatt, Inc.

www.iwatt.com

LED Characterization: An Arduino-Based Curve Tracer

Circuit Cellar columnist Ed Nisley doesn’t want to rely solely on datasheets to understand the values of LEDs in his collection. So he built a curve tracer to measure his LEDs’ specific characteristics.

Why was he so exacting?

“Most of the time, we take small light-emitting diodes for granted: connect one in series with a suitable resistor and voltage source, it lights up, then we expect it to work forever,” he says in his July column in Circuit Cellar. “A recent project prompted me to take a closer look at commodity 5-mm LEDs, because I intended to connect them in series for better efficiency from a fixed DC supply and in parallel to simplify the switching. Rather than depend on the values found in datasheets, I built a simple Arduino-based LED Curve Tracer to measure the actual characteristics of the LEDs I intended to use.”

The Arduino Pro Micro clone in this hand-wired LED Curve Tracer controls the LED current and measures the resulting voltage.

Ed decided to share the curve tracer with his Circuit Cellar readers.

“Even though this isn’t a research-grade instrument, it can provide useful data that helps demonstrate LED operation and shows why you must pay more attention to their needs,” he says.

Ed says that although he thinks of his circuit as an “LED Curve Tracer,” it doesn’t display its data.

“Instead, I create the graphs with data files captured from the Arduino serial port and processed through Gnuplot,” he says. “One advantage of that process is that I can tailor the graphs to suit the data, rather than depend on a single graphic format. One disadvantage is that I must run a program to visualize the measurements. Feel free to add a graphics display to your LED Curve Tracer and write the code to support it!”

He adds that “any circuit attached to an Arduino should provide its own power to avoid overloading the Arduino’s on-board regulator.”

“I used a regulated 7.5 VDC wall wart for both the Arduino Pro Mini board and the LED under test, because the relatively low voltage minimized the power dissipation in the Arduino regulator,” he says. “You could use a 9 VDC or 12 VDC supply.”

To read more about Ed’s curve tracer, check out Circuit Cellar’s July issue.

 

ALTspace – Cubes, Shame and Art

ALTSpace is a Community Art Workshop in Seattle. Creative people of all kinds share this spacious workshop, teaching, experimenting, making and learning. Members can spend time bouncing ideas off one another, hold or attend classes, work away from home and have the space to get even large projects done.

Location 2318 E. Cherry Street, Seattle, WA
Members 37
Website airlighttimespace.org

ALTspace hackerspace, Seattle

Co-founder Mike tells us about his space:
Tell us about your meeting space!

We have a total of about 2800 sq ft. We have two garage spaces for industrial machines, loud and dirty operations. (about 700 sq ft total) The rest of the space is for personal workspaces and public areas for working, meeting, hanging out. We have 2 showers, 2 bathrooms, a kitchen, a laundry room and an outdoor patio.

What tools do you have in your space? (Soldering stations? Oscilloscopes? 3-D printers?)

Full list of ALTspace’s tools & equipment.

Are there any tools your group really wants or needs?

A laser cutter would be our next purchase.

Does your group work with embedded tech (Arduino, Raspberry Pi, embedded security, MCU-based designs, etc.)?

Yes, we do quite a bit of electronics. One of our more well known projects, the Groovik’s Cube (A 30ft playable Rubik’s Cube) is an arduino driven project.

Can you tell us about some of your group’s recent tech projects?

Groovik’s Cube:

ALTspace's Groovik's CubeWe first built the cube as an art project for Burning Man 2009 and we’ve since been working hard to try and bring this project to the general public. We’ve been collaborating with the Science Center since summer ’10 and we’ve been doing a number of refurbishments including a brand new light-weight aluminum structure to create a neater look suitable for an indoor museum environment.

Groovik’s cube is a fully playable, LED driven Rubik’s cube, hung from the ceiling, corner down. (the motion is of course simulated, not mechanical, i.e. the colors move around, not the structure itself). It can be played and solved by the visitors. A particularly interesting feature is that we have split the controls into 3 stations placed around the cube, each allowing only one axis of rotation. This means 3 people have to collaborate together to solve it. The stations are ~30-50 ft apart from each other. This makes the puzzle considerably harder with a current record solution time of 50 minutes (achieved on Friday night @ Burning Man 09). It also turns a very introverted game into a collaborative challenge which is fun to watch. Imagine people shouting instructions to each other and running around checking on the state of the cube from different angles.

Temple of Shame:

ALTspace's Temple of Shame

by Alissa Mortenson, Nebunele Theatre, The Temple of Shame was a 6ft wide, 18ft tall wooden Temple dedicated to the collection of shame from the participants of Black Rock City. The temple was ceremonially burned on the last night of the festival to symbolically release all the shame collected.

From shameproject.org: “The experience of shame is part of our shared humanity, yet paradoxically, the times when we are ashamed are the times when we feel most alone. But within shame lies a capacity for human connection. The Shame Bearers seek to explore this emotion as a powerful medium for reaching a state of shared vulnerability. In order to make connection –the core human desire– we must believe that we are enough, that we are worthy of love and acceptance. In our vulnerability and our recognition of our mutual imperfections, we can find worthiness and connection. That is the power of this project.”

What’s the craziest project your group or group members have completed?

Groovik’s cube for sure.

Do you have any events or initiatives you’d like to tell us about? Where can we learn more about it?

Indeed: http://lsc.org/grooviks. We’re trying to raise funding for a new Groovik’s cube that will travel the World for 7 years together with Liberty Science Center and Erno Rubik!

What would you like to say to fellow hackers out there?

Hack more! Not satified with availability of hackerspaces near you ? Start one! It’s easier than you think and people come out of the woodwork to come and help and donate time and tools.

ALTspace’s tools & equipment:

Metal:

  • 2HP Metal Mill & Lathe
  • Lincoln 220 MIG Welder (up to 1/4″ steel)
  • TIG 200Amp DC/AC (i.e. Steel, Aluminum & other non-ferrous)
  • Plasma Torch (Up to 1″ steel or aluminum)
  • Stick Welder
  • Metal Grinding wheels, belt sanders
  • 4×6 Metal Bandsaw
  • Deburring wheel and 2 buffers
  • Wire bender
  • Abrasive metal chop saw

Machine Shop (Wood):

  • 3/4HP Table saw
  • Router table & Hand Router
  • Various Sanders (Orbital & Belt)
  • Miter Chop saw

Other Machine Shop amenities:

  • 90 PSI Compressor
  • 3/4HP 1/2″ Shank Drill press
  • Hand drills, Sander
  • 110V/230V Power (50A)

Glass:

  • Glass fusing/slumping/casting kiln, up to 1600 deg F

Jewelery setup:

  • Small Propane/Oxygen torch for soldering/annealing
  • Flexshaft Rotary grinder
  • Rolling Mill
  • Disc Die Cutter & Hemisphere punch

Electronics benches:

  • Maker bot
  • Soldering station with fume extractor and static pad
  • Multimeter
  • 100 Mhz Oscilloscope (Techronix)
  • Basic tools (snippers, strippers, screwdrivers, etc)
  • Variable voltage / current power supply
  • Stock of common components
  • Anti-static worktop

Sewing Area:

  • Pfaff industrial sewing machine
  • Janome domestic sewing machine
  • Hoseki HK757G is a 5-thread industrial serger
  • White domestic 4-thread serger
  • irons, cork-topped layout table, digitizing table, pattern plotter
  • Janome Computerized domestic sewing machine
  • Rowenta domestic iron
  • Sleeve board
  • Tailor’s ham
  • Pattern Drafting Rulers and curves
  • Costuming books

Read more about ALTspace’s Groovik’s Cube project on indiegogo or on Mike’s website, or about The Shame Project on shameproject.org!

You can read about more of ALTspace’s projects on their art page.

Show us your hackerspace! Tell us about your group! Where does your group design, hack, create, program, debug, and innovate? Do you work in a 20′ × 20′ space in an old warehouse? Do you share a small space in a university lab? Do you meet at a local coffee shop or bar? What sort of electronics projects do you work on? Submit your hackerspace and we might feature you on our website!