"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you"
Is there a good visual way to see what capacitors & transistors do? While I’ve read the descriptions of what they do, I’m more of a visual person who would like an “ah ha” moment… Thanks!
Prior to teaching our freshman to program microcontrollers, we introduce them to basic breadboard electronics and try to emulate the functions of the microcontroller. It just so happens three of the simple circuits, the LED flip-flop, LED dimmer and transistor amplifier, help to demo the use of a transistor and capacitor. The advantage of using LED circuits, is that it gives you visual feedback. There are also a million other simple circuits that demo transistors and capacitors using things like buzzers, photo-resistors, etc…..I just happen to like these.
The first circuit, an LED dimmer, uses the capacitors ability to store electrical energy (like a battery) and discharge it through the circuit when the primary power is removed. I liked this site, because the author has the circuit’s output connected to a ‘scope and gives a nice visual to the falling voltage, although I don’t condone their breadboard tidiness.
The second circuit, the LED flip-flop, demonstrates the use of transistors to switch on and off a pair of LEDs. This action is controlled by the two base resistors and capacitors in the circuit (RC circuit). When you increase the value of the capacitors the switching frequency slows down and vice versa.
The third circuit, a transistor amplifier, shows a nice demonstration of using a transistor to amplify a high resistance input in order to light an LED. I liked the general description of how a transistor functions as well as using a darlington pair to produce a high-gain amplifier.
These are just two examples that help to visualize the components use. If you are interested in diving deeper, looking at things like filters, you might want to get a scope (i happen to like my DSO nano as it’s cheap and easy to use).
I hope this has helped to answer your question and good luck with your circuits!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
Back in March you guys gave us a discount on LPD8805 LED strips, which was very sweet. Since then, our project has made some wonderful progress, and now that we have a website and kickstarter project up, I wanted to check in and say thanks.
For a bit of background, the SoundPuddle is an art installation inside a 24-foot wide dome, in which any sound you make creates ripples of color on a canopy of thousands of LEDs. It’s an interactive space of visual-acoustic synesthesia, and it’s sort of like a rudimentary holodeck. It may be the world’s only immersive sound visualizer. All of the sound inside the space is created by participants, encouraging people to play with and explore the sound spectrum.
The project is entirely open source, and all of our code so far is available on github (github.com/soundpuddle). Alvaro Lopes, the creator of the Zpuino project (alvie.com/zpuino/index.html), and myself (John English) were the electronics engineers for the project. Incase you’re not familier, the Zpuino platform we’re using is rather awesome, because it’s an Arduino compatible framework running on an FPGA. It’s much much more powerful and flexible than conventional Arduino hardware, but still very accessible and capable of using existing Arduino code.
Anyway, our website is up at: soundpuddle.org. We gave you guys a shout out on our about us page.
We’ve also just launched a kickstarter campaign for the project, so we can expand the LED array, and make other improvements and repairs to the installation. Those upgrades will allow it to go to Burning Man, Apogaea once again, and hopefully several Maker Faires. If it fits your interest, we’d be delighted for Adafruit to make a post about the project / kickstarter. We could definitely use all the publicity we can get (and we’ll turn around a buy more LEDs with the funding :p).
Whatever the case, we’re very grateful for your support back in March. That helped make the project possible, and it makes us feel good working with open source friendly companies such as yours.
What would be a good way to gauge the height of my model rocket?
Well, there are really quite a few ways to make the measurement. In a perfect world, your rocket launches perpendicular to the earth’s surface, and you can use a trigonometry to calculate the altitude based on your distance from the launch pad and the apparent angle from you to the rocket. You can use a tool, such as an inclinometer or “altitude tracker,” which uses your line of site to the rocket and references it to a string held vertically due to gravity. You then record your angle when the rocket hits apogee and through trig or the supplied calculator, you can determine the height. The problem with this method is that it doesn’t take into account any drift, which changes the your distance to the rocket and skews the measurement.
Alternatively you can use the same method, but with two observers. NASA has a nice description and calculator that does the trig for you and gives you a much more accurate measurement.
Another method it to buy a altimeter like a PerfectFlite APRA Altimeter. This device uses a barometer and returns a beep corresponding to the altitude an achieved velocity. You can also find more sophisticated devices that have computer interfaces, GPS, temperature, etc.
I hope this answers your question, and have fun with you calculations!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
After voting for the LEGO® CUUSOO – Ladyada’s Workshop! project, I submitted this sine-wave-drawing gadget: http://lego.cuusoo.com/ideas/view/17603 . In the comments, @kiff9 wrote, “”I am having trouble understanding…. Could you explain in words that would make sense to a 13 year-old?”". I’m happy that kiff9 spoke up! I want to give a good answer and I’m seeking professional help .
So, my Ask-an-Educator question is: How do I explain this sine-wave-drawing contraption in words that would make sense to a 13 year-old?
Nice gadget! Very simple, yet effective.
As for explaining a sine wave to a 13 year old, I would start with a jump-rope. If two people stand apart holding a jump-rope (or any rope really) and one person begins to move the rope up and down so that it makes a complete 1-node standing wave. If the two people move closer together, while maintaining the complete wave, then you are increasing the amplitude and vice versa. Then if one person begins to move the rope up and down faster so that you make a 2-node standing wave, you have increased the frequency. Have them continue to see how many nodes they can make. Finally, if you wanted to you could have the two people walk in one direction while maintaining their wave and you have demonstrated a phase shift
Another way of to demo a sine wave is with a wave generator. This java app allows you to display and manipulate a mathematically based sine wave.
Good luck with your explanation and I hope I have helped!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
NEW PRODUCT – Raspberry Pi – Skill badge, iron-on patch. You are learning to use the small Linux based board, the Raspberry Pi! Adafruit offers a fun and exciting “badges” of achievement for electronics, science and engineering. We believe everyone should be able to be rewarded for learning a useful skill, a badge is just one of the many ways to show and share.
This is the “I made something with a Raspberry Pi” badge for use with educators, classrooms, workshops, Maker Faires, TechShops, Hackerspaces, Makerspaces and around the world to reward beginners on their skill building journey!
This beautiful badge is made in the USA.
The badge is skillfully designed and sturdily made to last a life time, the backing is iron-on but the badge can also be sewn on.
Badge created with permission from the Raspberry Pi Foundation. A portion of the sale of each Raspberry Pi badge goes to the Raspberry Pi Foundation.
What is the Raspberry Pi® ? A low-cost ARM GNU/Linux box.
The Raspberry Pi® is a single-board computer developed in the UK by the Raspberry Pi Foundation with the intention of stimulating the teaching of basic computer science in schools. The design is based on a Broadcom BCM2835 system on a chip (SoC), which includes an ARM1176JZF-S 700 MHz processor, VideoCore IV GPU, and 256 megabytes of RAM. The design does not include a built-in hard disk or solid-state drive, instead relying on an SD card for booting and long-term storage. The Foundation plans to support Fedora Linux as the initial system software package/distribution, with support for Debian and Arch Linux as well – Wikipedia.
Raspberry Pi® is a trademark of the Raspberry Pi Foundation.
Adafruit’s badges are manufactured in partnership with AMBRO Manufacturing located in NJ, USA. AMBRO is a family owned and operated business since 1990 that celebrates open-source with Adafruit Industries. You can meet their team here. AMBRO uses non-toxic soy based, water soluble and environmentally friendly printing supplies, threads and more when possible. AMBRO has over 250 solar panels that generate 50,000 Kilowatt hours per year. Their equipment runs solar powered, so the wonderful things AMBRO and Adafruit have worked together on are made with the sun! AMBRO Manufacturing was recognized by Impressions Magazine, a leading trade publication in the garment printing and embroidery business, who published an article highlighting AMBRO and their commitment to their environmentally focused manufacturing practices. Adafruit knows you have a lot of choices as to where you spend your money and time, we hope our open-source values, commitment to green technologies and partners helps make the decision easier and fun!
I have a question. I have a cuttable El Sheet panel which has 4 connector pins, 1 for each side.
If I have cut out my shapes and used up these pins but still have some leftover el sheet. How do i use the remainder el sheet without any connector pins?
Do I solder onto the el panel tabs or is this too risky? What methods are available if I want to use these bits of the El Sheet which don’t have connector pins?
Would you suggest wire glue? I haven’t seen anyone answer this question yet, so thought I would ask!
Thank You
This is a great question as I am sure this is not a unique problem!
Short answer to your question is yes (well probably yes, I don’t have any on hand so this is hypothetical. Please chime in on the topic if they have/have not had success)….but looks like it will be a bit tricky. If you look at the cross-section of your el sheet, you are going to have to remove a small amount of material in order to expose conductive ITO layer. You should be able to do this by carefully scraping through the rear protective film, rear electrode, and phosphor dielectric or by going through the cover protective film on the front. Once you have exposed a small amount of ITO layer, I would recommend using a drop of wire glue to connect your electrode. Make sure you you have completely cleaned and isolated the ITO + wire glue bond from the phosphor and rear electrode as it will produce an electrical short. For the rear electrode, you should just be able to carefully remove the protective film and attach your wire with a drop of wire glue.
Let us know how it goes. It is always fun to experiment and see just what you can do!
I hope this has helped and as I asked before, if anyone has, or wants to give it a try, let us know how it goes!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
You can use your own brainwaves to bring you the rest you need! That’s why we designed the NeuroDreamer sleep mask. Through ambient music and gently fading lights the NeuroDreamer sleep mask weaves a subtle spectrum of brainwave frequencies — the same spectrum that naturally appear in a person as they fall asleep. Simply close your eyes and listen to the music, and let your brainwaves do the rest…
Mitch will also be at The Next HOPE conference July 16-18.
Just turned 34 today and my GF got me some new badges for my birthday so I thought I would update the thread with the new ones added
Since the original post I’ve added Dumpster Diving, PHP Elephant (thank you for making this one!), Android, Magic Blue Smoke Monster, QR Code, and Multi-meter.
PHP – Skill badge! - You learned PHP! PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. Adafruit offers a fun and exciting “badges” of achievement for electronics, science and engineering. We believe everyone should be able to be rewarded for learning a useful skill, a badge is just one of the many ways to show and share.
The badge is skillfully designed and sturdily made to last a life time, the backing is iron-on but the badge can also be sewn on.
One of most requested new badge for us to add was one for PHP. So we talked wth Vincent who designed the very cute PHP elephant and we now have permission to make these! The elePHPant created by Vincent PONTIER – www.elroubio.net Adafruit has permission directly from Vincent to make this wonderful badge! Read more about PHP here.
Adafruit’s embroidered badges are manufactured in partnership with AMBRO Manufacturing located in NJ, USA. AMBRO is a family owned and operated business since 1990 that celebrates open-source with Adafruit Industries. You can meet their team here. AMBRO uses non-toxic soy based, water soluble and environmentally friendly printing supplies, threads and more when possible. AMBRO has over 250 solar panels that generate 50,000 Kilowatt hours per year. Their equipment runs solar powered, so the wonderful things AMBRO and Adafruit have worked together on are made with the sun! AMBRO Manufacturing was recognized by Impressions Magazine, a leading trade publication in the garment printing and embroidery business, who published an article highlighting AMBRO and their commitment to their environmentally focused manufacturing practices. Adafruit knows you have a lot of choices as to where you spend your money and time, we hope our open-source values, commitment to green technologies and partners helps make the decision easier and fun!
I wanted to share an app that I created to control and monitor my various electronics projects. It uses Bluetooth, is highly customizable and is very easy to integrate. I always put a lot of thought into how I’m going to control and monitor a new project and this app was the ultimate result. I use it for everything now. It really changed the way I thought about interacting with my projects and I hope your readers will find it useful.
I just LOVE receiving things from you only few days after sending order. I can’t wait till evening to assemble it. You do a great job with this ‘open hardware’ and with popularization of electronics. I hope that by shopping in your store I can support you.
Getting the big question right out of the way: no, we won’t be selling these. Legally, we can’t, for trademark reasons. But it’s generally okay for anyone to create replica props for their own personal use, so we hope this writeup will inspire some cool projects among our readers…
I need a cheap universal joint for a project I am working on so I have been playing with a few options. This is the one that seems the best so far. It is using a plastic ball from a wall track toy which is pretty far from a perfect sphere but it seems to work very well anyway. For the project I will use a cheap 1/2″ steel bearing and laser cut the pieces from Delrin which has low friction. I will probably use nylock nuts on the screws to be able to adjust how stiff the movement is.
The tiny, super-cheap PC is largely aimed at teaching kids how computers work and hopefully getting them interested in programming. It makes sense, then, that one of the first of the sought-after unitswent to the Boreatton Scout Troop, 10 members of which are in a robotics team that competes with similar groups internationally.
There’s a ton of software out there that lets you design things that will eventually be printed with 3d printers, but what about designing the 3d printers themselves? Say you wanted to design your own 3d printer; something akin to a Makerbot, ORD bot or a RepRap. What software would you use to design and model the printer itself?
Interesting question! Whenever I begin the design process, I take a look at the manufacturing tools I have available and design around their capability. For example, I LOVE my laser cutter. If I could recommend any one piece of Maker equipment to everyone, it would be the laser cutter. Its versatility and ease of use make prototyping a breeze. I also have available to me a pretty large amount of CNC machinery including lathes, mills, 3D printers. Each one of these pieces of equipment require different types of software to take a design and create a product.
If you are looking to create your 3D printer from ~2D material, like the ply they use on the MakerBot and have it cut on a Laser Cutter, I would recommend 2D drawing software like DraftSight. Very similar to AutoCAD, DraftSight provides a very capable FREE work environment to produce line drawings. These are then exported as a DXF/DWG and are interpreted by the laser cutter to make the appropriate cuts.
If you are looking to create a 3D printer like a RepRap, that uses complex 3D components, I would recommend 3D drawing software like Solidworks or AutoDesk Inventor. Both of these pieces of software are offered as trials and have student versions for relatively cheap. (You could use Sketchup with the STL plugin….but I find it to be a bit limited and slow)The designs you produce with the software are then saved as solid object files (STL or equivalent), deconstructed into g-code through a processor, then read by the machine to produce the part.
This is the sequence of steps I used to build my 3D printer:
2D Parts:
Hand sketch the idea
Dimension the drive components (steppers, pulleys, bearing mounts, etc.)
AutoCAD to create the designs for the acrylic pieces
Print through Epilog Print Driver configured for cutting
3D Parts:
Hand sketch the idea
Dimension the space in which the part will occupy/support/etc.
Solidworks to solid model the part
Export as an STL
ReplicatorG to generate the g-code and run the machine
As reference, the CNC Panel Joinery Notebook has a ton of great examples of joining components. A good example is the “Pettis Joint,” as it was highly utilized in the MakerBot design.
I hope this has helped to answer your question and good luck making your printer!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
I was having fun with some home-schooled 1st (approximately) graders, they were absolutely loving making LEDs light up on a breadboard, and discharging caps through them, but had no idea of what was happening.
How can I explain concepts like current, voltage and series and parallel to kids who can’t yet multiply and divide? Or in fact, should I even be trying? If so, do you think the hydraulic analogy would be a good way to visualize it?
Any suggestions for what other cool things can we make that are still at that level?
EXCELLENT question and you will be surprised at how much a 7 year old can grasp, especially when you use hands on activities. When you are working with such a young crowd, it is very easy to lose their attention and you need to be realistic in what concepts you want them to hold on to. This being said, I would recommend your hydraulic analogy in tandem with hands on activities that reinforce the theory. Have them use buckets, tubing, clamps of some sort and a water wheel to simulate the flow of electricity. After such a lab, I would expect them to retain the idea that electricity can mimic the flow of water and altering the flow can emulate discrete components and result in a different outcome.
There are a bunch of products out that help to simplify the use and understanding of electronics. The first that comes to mind is littleBits, which “consist of tiny circuit-boards with simple, unique functions engineered to snap together with magnets. No soldering, no wiring, no programming, just snap and play.” Another idea would be to work with Squishy Circuits, which “uses tools and activities [that] allow kids of all ages to create circuits and explore electronics using play dough.”
Also, have you thought about introducing programming? There are a bunch of languages (like Scratch and App Inventor) and microcontrollers that allow the students to both construct with simple programs and circuits as well as tinker with the outcomes. I had run a post earlier answering a question about programming microcontrollers with 12yr olds. It and it’s comments section might give you some ideas. I ran another post on teaching STEM concepts to 1st/2nd graders that might be useful as well.
I hope I have helped to answer your question and best of luck with your 1st graders!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
Star Trek’s holodeck technology may no longer remain the stuff of fantasy as developments in 3D technology bring us ever closer to life-like holographic images.
Sharp Labs Europe are currently working on a cutting-edge communication technology that they hope will make 3D images indistinguishable from reality. The idea is that in the future we will be able to communicate in a simulated reality, that could give us the option of interacting with each other without leaving our homes.
The State of Open Source Hardware
Dustyn Roberts, Catarina Mota
In the last few years, open source hardware went from an obscure hobby to a burgeoning movement built on values and practices derived from open source software, hacker culture, and craft traditions. This increase is visible in the exponential growth of the community of developers and users, the increase in the number and revenue of open source hardware businesses, and the emergence of a large number of new DIY gadgets and machinery – from 3D printers and microcontrollers to soft circuits and tech crafts. The accessibility of hardware plans, along with the communities and collaborative practices that surround them, is lowering the barrier to entry and encouraging people of all ages and walks of life to create, hack, and re-purpose hardware. Taken together, hackerspaces, the increasing accessibility of digital fabricators, and these open and collaborative practices are leading to an explosion of creativity and innovation reminiscent of the golden years of the Homebrew Computer Club. This panel will go over the defining events of the last few years to draw a snapshot of the current state of the open source hardware movement and the impact it’s having in hacker culture and beyond. Also included in the discussion will be the Open Hardware Summit: the world’s first comprehensive conference on open hardware, and how it will serve as a venue to discuss and draw attention to the rapidly growing open source hardware movement.
“Have you ever been in a certain mood and reached for a song you’d hoped would ‘fit’ but couldn’t find anything? Or maybe you’d like to hear a song on a particular topic? I’m curious to know if there’s a song ‘void’. Maybe there are many?” These were the questions that lead British singer-songwriter Imogen Heap to collaborate with designer Moritz Waldemeyer. The outcome is the Listening Chair, an egg-shaped chair which doubles as a recording studio, designed to travel around the world asking people the question: “What is the song that still needs to be written?”
Khan Academy, an educational non-profit, is becoming one of the sexiest workplaces for programmers in Silicon Valley, where stock options, IPOs and big-money acquisitions have long been considered key to luring talent. It’s attracted star coders from companies like Google and Microsoft and, as it grows, has its pick of some of the tech sector’s top engineers.
Khan’s recruiting success underlines something often forgotten as investment dollars pour in to the Valley: Money isn’t everything. At Khan, none of the staff can hope for a fast fortune. What they can realistically hope for is to shape a nascent industry and to markedly improve the lives of millions of students. It turns out that means a lot.
Good afternoon all. I wanted to show you guys my project and possibly get some feedback. I home brew beer and, during the (Texas) summer, I have a problem keeping my house at a temperature that is within the ideal conditions required for the yeast to thrive during the fermentation process. So a common solution to this is to create a fermentation chamber to allow your beer to ferment in a controlled environment. Many people use a chest freezer with an additional thermostat for this. There are a couple non-programmable thermostats available that work very well.
However, when brewing a lager-type beer, a more complex temperature profile is required for ideal fermenting conditions. For instance, a typical lager fermentation could be: Lower the temperature from 76 to 52 degrees over a period of 24 hours, hold temp at 52 for 10 days. Slowly raise temperature to 68 degrees over a period of 24-48 hours, then lower the temp to 34 degrees over a period of 48 hours and then keep it at 34 for 6 weeks.
This sequence of temperature is a lot of work and dedication (especially for someone with as short of an attention span as myself) for a manual thermostat. So I have created a programmable thermostat to control my fermentation chamber. I created it with a PIC18F microcontroller, a TMP36 temperature reading IC, and a relay. I created a user interface with the help of a 16×2 character LCD and an up/down/select keypad arrangement.
I have a ‘Default Lager’ program built into the thermostat (not surprisingly, very similar to the one described above), but I also added a function to be able to create your own temperature profile or edit a currently saved one.
I have added functionality for the user to navigate through the program to any stage/time the user wants.
I’ve just finished up with this, I am currently testing it out and working out a few little bugs here and there, but I hope to be able to put this to work very soon. Being able to brew lager-type beers opens up a whole new set of beer recipes to brew (and drink! )
We MIGHT have a special guest if the timing works out! KATE HARTMAN!
Kate Hartman is an artist, technologist, and educator whose work spans the fields of physical computing, wearable electronics, and conceptual art. She is the co-creator of Botanicalls, a system that lets thirsty plants place phone calls for human help, and the Lilypad XBee, a sewable radio transceiver that allows your clothing to communicate. Her work has been exhibited internationally and featured by the New York Times, BBC, CBC, NPR, in books such as “Fashionable Technology” and “Art Science Now”. She was a speaker at TED 2011 and her work is included in the permanent collection of the Museum of Modern Art in New York. Hartman is based in Toronto at OCAD University where she is the Assistant Professor of Wearable & Mobile Technology, the Director of the Social Body Lab, and the interim Director of the Digital Futures graduate program. She is also the director of ITP Camp, a summer program at ITP/NYU. Hartman enjoys bicycles, rock climbing, and someday hopes to work in Antarctica.
What is “Ask an engineer”? From the electronics enthusiast to the professional community – “Ask an Engineer” has a little bit of everything for everyone. If you’re a beginner, or a seasoned engineer – stop in and see what we’re up to! We have demos of projects and products we’re working on, we answer your engineering and electronics questions and we have a trivia question + give away each week. Mosfet the cat stops by too. Previous chats can be viewed at http://www.adafruit.com/ask
And don’t forget, 30 minutes before the show we’re doing our weekly show-and-tell. If you are on Google+ and want to join, just add/follow +Limor Fried’s (Ladyada) page and post a comment so you can be added to the show and tell circle. At 9:30pm ET you will see a link to the hang out. Just keep your mics muted until we call on you and have your project ready.
For those who just want to watch, you’ll be able to watch it live on Ustream here and we usually have a recorded version posted later.
The very awesome Dorkbot PCB service, run by the amazing Laen, now has a new ordering system, OSH Park.
This is a community printed circuit board (PCB) order. We take designs from lots of people, put them all together on a panel and then order the panel from a fab.
Since we’re all splitting the panel setup cost, this lets us make circuit boards inexpensively.
This service grew out of the DorkbotPDX PCB Order run by by @laen and now comprises of a two-layer panel every other day, a four-layer panel every three weeks and a periodic two-layer medium run service for people needing more than 150 square inches of board.
This was the PCB service I used to prototype the Coobro Geo, and I have always had a great experience with other PCB orders. Hopefully this new system will help Laen keep up with the ever growing OSHW community!
How do I choose resistors to match a multiplexed led matrix?
Great question and the answer is a little elusive. Let’s at the diagram for Adafruit’s 8×8 matrix:
As you might know, there are many ways to drive a LED Matrix, and we will assume you have an 8×8. The easiest is to drive it directly from your microcontroller using 8 pins for the anodes and 8 for the cathode. With this configuration you can individually control all 64 LEDs and have a variety of methods for switching them on and off. If you look at the I/O capability of your microcontroller you will notice that they are only capable of sinking ~30-40mA per pin. If you were to were to illuminate an entire row with a common cathode, you would draw ~160mA and blow out your controller.
First the math:
If you look at the spec sheet for Adafruit’s matrix, the LEDs have a Vf of 2.2V and draw 25mA. In order to properly illuminate them with a 5V supply you would need a 112ohm (120ohm is the closest without going below) resistor. R = (5V – 2.2V) / 0.025A = 112ohm.
The problem with using a 120ohm resistor in series with the anode of each column is that when you illuminate more then one row at a time, the current available for each LED decreases…so you will get an uneven illumination of the panel.
If you run the calculation for 8 LEDs in parallel, you would need 14ohm (15ohm is the closest without going over) resistors to deliver 25mA to each LED. The problem with this is that the voltage is going to increase across each diode when less then 8 are illuminated, and you would be drawing 200mA! Far more then your microcontroller can handle.
This brings us to our control theory:
Method 1:
Since you are multiplexing the LEDs you can take advantage your processors high speed by “scanning” the grid. With just your microcontroller, you can illuminate each LED with a 60hz refresh rate so you eyes dont see the flicker. You could implement an algorithm to scan from the top left to bottom right (just like a CRT). This would allow you to run an entire panel with relatively low current draw. Arduino.cc has a good overview, although they are not using the scan method, and don’t forget the dropping resistors.
Method 2:
You can use your microcontroller to control more then one row at a time by controlling the anodes and cathodes with MOSFETs. This would allow for you to run your panel at even higher current ratings then the “constant on” current from the data sheet. You can change the duty-cycle controlling the rows to allow for ~100mA per diode. You will get a much higher brightness, and if you cycle them at >60hz, you eyes wont really notice the flicker. Here is a good example using 2n3906 and 2n2222 transistors.
Method 3:
You can also accommodate for the high current loads through the matrix by using a stand alone multiplexer. The IC allows you to isolate your microcontroller and allow you to take greater advantage of multiplexing by controlling more then one row at a time. Arduino.cc has a list of tutorials as well for setting up a matrix using drivers.
I hope this has helped to answer your question and good luck with your matrix!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
Thank you all for your previous questions! I hope you have enjoyed the answers and look forward to your future responses.
My question jar is running a bit low, so don’t forget to submit your inquiry via the link below!
For those of you who are new to the scene, I have been teaching high school courses in Energy Systems and Systems Engineering for the past 7 years and use a significant amount of today’s hackerspace technology in my curriculum. If you have any questions about utilizing things like laser engraver/cutters, 3D printers, Arduino, PICAXE, VEX, Vernier, etc. into your curriculum or just general use, I would love to share my opinion!
Don’t forget, everyone is invited to ask a question!
I’m a self-taught DIY’er, and have been learning electronics for some time now. As i’ve started building my 1st 3d printer, i have to use an Arduino Mega 2560. I’d rather learn how to use an Arduino properly, instead of just dumping code into it and let it run.
So my question is, what is the difference between a microcontroller (Arduino and Arduino-like platforms) and something like a BeagleBoard/Bone or a RaspberryPi (I realise these a full-blown computers)? What are they intended uses for each type of platform; when should you use one or the other? What are they, and what are they not?
Great question. Comparing Arduino to something like BeagleBoard or Raspberry Pi is like comparing a calculator to a laptop. They each have their purpose. The Arduino platform is designed around a relatively low power microcontroller that gives the user complete control of its hardware. Through the use of the Arduino IDE, you can write programs (<32Kb) that can interface with almost limitless hardware including switches, sensors, LCDs, other microcontrollers, the internet, etc.
Regarding devices like Raspberry Pi and BeagleBoard, they are designed to function on a much higher level. With already integrated hardware that takes care of things like ethernet, video and audio processing, large quantities of RAM and an almost unlimited amount of storage space, they are really mini-computers. You are able to run complete operating systems, like Linux and Android, and develop programs within those operating systems that can control the systems functions and the IO that are made available.
If you were to design a control panel for a microwave, you could use an AVR like Arduino. It could drive the LCD, interface with the buttons, and sense the conditions inside the appliance. You could have also used a device like Raspberry Pi or BeagleBoard, but it would be overkill for the task. Now if your microwave needed a high resolution multi-touch LCD that Tweeted what you were cooking while checking your stocks…..
Below is a chart I threw together to compare the hardware between lower power devices like Arduino and Propeller to the big-guns like Raspberry Pi and BeagleBoard:
Good luck with your 3D printer. I just finished mine and went the route of an Arduino Uno + grblhield + Teacup firmware and have a pretty rock solid system. Just make sure you actively cool the grblhield on long runs.
I hope this has helped to answer your question!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
So you’ve spent a ton of time build and hopefully flying your quadcopter. Now you need something keep it safe in between flights!
At Techshop I built my own quadcopter using the laser cutters and some of the other tools and equipment available. One day though while driving around with the quadcopter in my truck another box rolled over on top of the quad and broke the main frame apart. That is was inspired me to build some sort of transportation / storage box for it.
What is the functional difference between stranded and solid-core wire?
Great question!
Solid wire consists of a single strand or core of wire that is insulated with non-conductive material. Typically you will find solid core wire in situations where the wire is not designed to be continuously flexed (i.e. your house electrical wiring, wires for breadboards, etc.)
Stranded wire consists of a bundle of small gauge wires compressed and insulated with non-conductive material. Typically you will find stranded wires in situations where the wire needs to be routed through tight spaces or experiences frequent flexing/vibration (i.e. headphone cables, speaker wire, automotive wire, appliance cables, etc.)
Some advantages of solid core wire:
Cheaper to produce
More compact diameter for the same current carrying capability as stranded
Less likely to fail due to corrosion
Disadvantages of solid core wire:
Typically only available in small gauges
Continuous flexing or vibration will cause the wire to fatigue and break
Some advantages of stranded wire:
Very flexible and withstands a greater amount of flexing and vibration
Easier to rout
Disadvantages of stranded wire:
Diameter is larger for the same carrying capability as solid
More costly to produce as the manufacturing process is more complex
More likely to fail due to corrosion from capillary action & a high surface area
I hope this has answered your question and good luck choosing the correct cable!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
I am now comfortable with my electronics prototyping to want to try some things with operational amplifiers. I am still having issues reading schematics I guess, because whatever I do, I cannot seem to set up what seems to be a simple non-inverting amplifier! I am using an LM358N on a breadboard. I see that using two resistors connected in a specific way should allow me to amplify the voltage I have going in to 2x. So if I have 5v going in, should I not get 10v in the output? I actually get something like 3.58v!
Maybe a more general question would be, what are some tips for going from a schematic to a breadboard!? I know it is meant to be simple, but I cannot seem to get intuitive about this!
Great question, and I have spent a few days finding a good way to answer it. Before we get to the circuit problem, you might want to take a look at Fritzing.
Fritzing is a
Electronic Design Automation software suite with a low entry barrier, suited for the needs of designers and artists. It uses the metaphor of the breadboard, so that it is easy to transfer your hardware sketch to the software. From there it is possible to create PCB layouts for turning it into a robust PCB yourself or by help of a manufacturer.
One of the nice features of Fritzing is its ability to switch between your schematic view and a breadboard. You can either populate the breadboard, and get a rudimentary schematic, or vice versa. This would allow you to take your op-amp circuit and create something like the following:
Regarding your 3.58V output, make sure that you are sufficiently powering your op-amp. Your non-inverting circuit is configured to output 10V from a 5V input. This input should be a signal input, as the op-amp can only drive a couple of mA. If you are looking to boost your voltage from 5V to 10V in a power application, you might want to check out a boost converter. If your application is to boost a signal voltage, check out Todd Toporski’s article about “…Violating your op amp’s input common-mode range” which illustrates the devices range of common-mode input voltages that result in proper operation of the device and how close the input can get to either supply rail. So if you look at the data sheet for the LM358, the input common-mode voltage range is V+ – 1.5V. Which means that if you power your device at 5V you will only be able to output ~3.5V…which might describe your measured output. You would want to power the op amp at a minimum of 11.5V in order to get your 10V output.
I hope this has answered your question and good luck with your breadboarding!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
In my morning news feed, I came across this great BBC interview with Linus Torvalds. One of my favorite things about Torvalds has always been his ability to grasp and succinctly explain technology in a wider social context. When asked here for his feelings on the Raspberry Pi, he does not disappoint:
The recent launch of the Raspberry Pi, running on Linux, has attracted a lot of attention. Are you hopeful it will inspire another generation of programmers who can contribute to the Linux kernel?
So I personally come from a “tinkering with computers” background, and yes, as a result I find things like Raspberry Pi to be an important thing: trying to make it possible for a wider group of people to tinker with computers and just playing around.
And making the computers cheap enough that you really can not only afford the hardware at a big scale, but perhaps more important, also “afford failure”.
By that I mean that I suspect a lot of them will go to kids who play with them a bit, but then decide that they just can’t care.
But that’s OK. If it’s cheap enough, you can afford to have a lot of “don’t cares” if then every once in a while you end up triggering even a fairly rare “do care” case.
So I actually think that if you make these kinds of platforms cheap enough – really “throw-away cheap” in a sense – the fact that you can be wasteful can be a good thing, if it means that you will reach a few kids you wouldn’t otherwise have reached.
Matthew Beckler (one half of the great Wayne & Layne duo) taught a KiCad class on Saturday at the HackPittsburgh maker space. The multi-part class will teach the participants how to design a physical circuit prototype on a breadboard, translating the breadboard design into KiCad, ordering the PCBs through a quick-turn PCB manufacturer, and then soldering up their own boards. At the end of the class, the participants will take home their own, completed circuit boards, and an official KiCad skill badge.
This sounds like a really great class, and we love to see our skill badges being put to use. If you live in the Pittsburgh area and are kicking yourself for missing the class, check out the HackPittsburgh website here, and hopefully Matthew will run another KiCad class in the future.
I’d really like to know how to “”convert”" an analog value to a digital one.
In a word : I have an Arduino, a photoresistor, with a pull-down resistor.
I want to know if the light is above or below a given threshold.
I know how to read the value with analogRead(photoResPin), and compare it to my threshold (in code), but I’d like to do that without software (only using digitalRead), handling that threshold in hardware.
Can you help me ?
I guess I can use a transistor, but don’t know how to “”precisely”" set the threshold (by changing the pull-down resistor value ?).
What a great question and the answer should be pretty easy to implement! As long as the current you need to control is relatively low, a simple comparator like the LM393 should do the trick. You can configure the comparator to act as a Schmitt Trigger, you can set a high and low threshold voltage using positive feedback as shown in the diagram below. This basically relies on two voltage dividers (R1/R2 & R2/R3) to set the high an low values, then uses R4 as a logic pull-up. By using this positive feedback you help to eliminate multiple transistons between a HIGH/LOW output when your input voltage approachs and hits you threshold, as illustrated in the second diagram. This feedback also helps to speed up the time in which the comparator changes state.
This Schmitt Trigger Calculator should help you determine the values for your resistors and R4 is commonly a 1k.
I hope this has helped to answer your question, and the topic of switching from microcontrollers to stand alone hardware is certainly on my lists of things to research further! So thanks to you!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
As prep for future projects, I’ve built a simple 2D array of individually addressable LEDs. This canvas will ultimately serve as the platform for some games (snake, pong, etc), but I’m hopeful that other people will find this useful and come up with some cool applications.
These LED strips are fun and glowy. There are 32 RGB LEDs per meter, and you can control each LED individually! Yes, that’s right, this is the digitally-addressable type of LED strip. You can set the color of each LED’s red, green and blue component with 7-bit PWM precision (so 21-bit color per pixel). The LEDs are controlled by shift-registers that are chained up down the strip so you can shorten or lengthen the strip. Only 2 digital output pins are required to send data down. The PWM is built into each chip so once you set the color you can stop talking to the strip and it will continue to PWM all the LEDs for you.
I wanted to see if the accelerometer breakout board could be used to make a game controlled by tilting. The result is a game where you help Mosfet the cat round up bouncing Adafruit logos.
The OLED is connected to the Arduino by following the wiring in the tutorial. The tilt sensor provides values in the range of 0 to 3.3v, but the Arduino expects values in the range of 0 to 5v. Looking through the Arduino documentation, the analogueReference function allows you to specify how the Arduino determines the top of the input range for analogue sensor reads. Passing the EXTERNAL option to it and connecting the 3.3v out pin on the ADXL335 breakout board to the AREF pin on the Arduino sets the top to 3.3v. In the end, I found that I didn’t need to worry about the range to this level for simple tilt sensing, but liked the idea of having the input ranges match.
The accelerometer is added to the circuit as below:
Arduino Uno image courtesy of Fritzing
In the code, the X and Y values from the sensor are flipped to match the OLED’s X and Y coordinates. Additionally, the sensor values are captured at startup to use as a reference point for “level” to determine the tilt of later reads:
// Assume the sensor is level, capture the current values as origin
origin_y = analogRead(X_IN_PIN);
origin_x = analogRead(Y_IN_PIN);
I found that the raw sensor reads were too sensitive for gameplay to be predictable. I handled this by dividing the change value by 10:
// Read the sensor values and swap coordinates to match OLED.
raw_sensor_x = analogRead(Y_IN_PIN);
raw_sensor_y = analogRead(X_IN_PIN);
// Center sensor reads on origin and reduce jitter.
tilt_sensor_x = (raw_sensor_x - origin_x) / 10;
tilt_sensor_y = (raw_sensor_y - origin_y) / 10;
Full source is available on github. I hope you enjoy playing Mosfet’s Roundup and I’d love to see what you’ve done with the tilt sensor.
This is a port of the Arduino based Arducopter Drone software to Flash for users to try AC’s features and to learn how to tune their drones. I hope it helps users learn more about PIDs, flight control, and sensors as well as prevent crashes of expensive drones!
how do i send/control the L293DNE motor driver to power a SOLENOID or just a dc motor
This is a really good question, and quite a popular topic. The L293D or DNE, depending on the manufacturer, is a Quadruple Half H-Driver or H-Bridge IC that allows for the control of high current loads from a low current source. The advantage of this chip over just using a transistor or MOSFET is in the fact that you can control the polarity of your motor when used as a full H-Driver.
If you are looking to just control a solenoid, I would recommend using a transistor. Specifically one that can handle the relatively high current loads like a TIP120 or equiv. This transistor with a base resistor will be able to drive ~1A from just about any microcontroller. This can also be used to drive your motor and I actually ran a post earlier which gives a much more in depth overview.
Regarding your L293D, below is a circuit diagram that illustrates 3 possible configurations for driving a motor. The one the left shows the IC being used as a full H-Bridge. The pins are configured as follows:
Pin 1 (1/2 Enable) – Channel 1/2 enable HIGH = ON
Pin 2 (1A) – Channel 1 logic control
Pin 3 (1Y) – Motor Lead
Pin 4 – GND
Pin 5 – GND
Pin 6 (2Y) – Motor Lead
Pin 7 (2A) – Channel 2 logic control
Pin 8 (Vcc2) – Motor Power Supply
To turn CW, make 1A HIGH and 2A LOW. To turn CCW, make 1A LOW and 2A HIGH.
The diagram on the top and bottom right show how you can control your motor in one direction. The top right diagram shows the motor being controlled on the HIGH side and the bottom right diagram shows the motor begin controlled on the LOW side. The control scheme is essentially the same as above, though you will only be controlling one of the logic control lines.
I hope this has helped to answer you question and clarify the use of the L293D!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
What are some quality resources for helping teachers prepare lesson plans with STEM material?
I am a Software Engineer that is helping my former high school develop their new STEM program, and would like to have some resources to help fine tune their classes, with both real world and class room material.
These Q/A posts have been very instrumental in the development of the program and I greatly appreciate your input.
This sounds like a great project and I am happy to hear you are helping out your former high school. It is really great when industry itself helps to develop STEM in education. Especially when the teachers are allowed to work with the individuals to help better their understanding about what is actually happening in the “real world.” This is one of the things that has always bothered me about being a teacher. I spend every school year preparing my students to enter higher education and later the work force ….. a place that I have really never been. Although I spend a great deal of time working in industry over my summers and researching the hell out of my curriculum, I will never fully understand what is actually happening in jobs I am prepping my students for. (Lack of this understanding is a real problem BTW…….I have actually heard of teachers LAMINATING their notes!)
This is where you come in.
You have been given an opportunity to help tailor an UP-TO-DATE STEM program for your school and are bringing knowledge to the table that textbooks can never supply. Kudos to you!
STEM programs can be a bit funny as Science and Math are required courses. And being required courses, they have required curriculum with standards testing to verify the students grasp. Updating the curriculum requires imaginative teachers that can both inject new and interesting topics into the classroom while hitting all of their benchmarks. In my opinion, the real opportunities in developing and bettering STEM in a school is through the Technology and Engineering. (Engineering is a bit funny too. What qualifies as an actual Engineering course in K-12 as apposed to a Technology course?)
Tech Ed is the needle in the rough. Although there are state and national standards for Tech Ed curriculum, there isn’t any national testing. Typically schools validate their Tech Ed programs through vocational and industry based certification tests. Talk about an open door. If you have an administration that is flexible and progressive enough, you can honestly propose just about anything intellectually stimulating that focuses on Engineering. How about a course in Aeronautics…….and not just Balsa Planes or Rockets or whatever…..but rather a course in Quad Copter flight dynamics? Take the state Aeronautics course code, meet the curriculum requirements, get it approved and BAM you have a course that will blow the students minds.
As for resources, there are tons. Here are just a few:
INTEL – Intel inspires the next generation of innovators with Science, Technology, Engineering and Mathematics (STEM) curriculum, competitions, and online resources to encourage students’ interest and participation.
NASA – NASA’s Education Materials Finder will help teachers locate resources that can be used in the classroom.
EPA – At EPA, we want to provide you a tool for talking about environmental issues. Or provide you a place to share environmental tips and ideas that you use every day.
PUMAS – PUMAS (poo’ • mas) — is a collection of brief examples showing how math and science topics taught in K-12 classes can be used in interesting settings, including every day life.
STEM Connect – STEM Connect is the captivating real-world STEM curriculum and career development resource from Discovery Education.
Museum of Science – “Engineering the Future” is intended to help today’s high school students understand the ways in which they will engineer the world of the future — whether or not they choose to pursue technical careers.
Best of luck and I hope I have helped with your question!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
I’ve got a Bluetooth stereo adapter I’m powering with the Aux port in my car. When I go from Aux standby to the engine running, the power cuts for a moment and I have to reconnect. Can I add a capacitor, or some sort of battery backup that will keep the device on for the 2-3 seconds the port switches off?
Part 2: The same bluetooth adapter makes audible noise on the stereo not connected to it’s audio output. For instance, a blinking light shows the device isn’t connected, and while it’s blinking, you can hear ground hum coming on and off (matching the light). As well, when the adapter is connecting to another device, you can hear muffled, modulated sounds (reminds me a bit of an old modem) – these are separate from the audible beep that happens when the bluetooth connection completes.
What are these noises? Can they be isolated from the audio output?
This actually isn’t too hard of a task. Right now the power going to your 12V AUX port in your car is connected to the ignition circuit. Power is cut to this circuit when you start the engine because of the large power demands your starter puts on your car’s 12V battery. There are 12V circuits in your car that never cut off during this period, like power to your ECU. If you look at the wiring diagram for your car’s ignition, you can isolate which lines are controlled by the different positions of your ignition switch. I would recommend that you connect to a circuit that stays on during all key positions except for OFF. This way you don’t run your battery down while you are not in your car.
In order to make this modification, you are typically going to need to remove the your center console bezel to expose the lines running to your outlet. Before you try and tackle any electrical modification to your car DISCONNECT THE BATTERY! BOTH + and – just to be one the safe side. At the outlet there will most likely be three lines: one for 12V, one for GND, and one for the light. You will want to cut the 12V and heat shrink the end on the hot side to prevent it from shorting. You will then need to run a simillary sized gauge wire from the outlet to the determined electrical line and solder splice the connection. You can use mechanical splices like wire nuts, wire taps or crimps, but they will eventually fail from vibration. Make sure you use heat shrink or electrical tape to prevent shortage. Finally, reconnect your battery and check the power to the outlet with a multimeter prior to plugging in your bluetooth unit.
Regarding your audio noise problem, it happens to be very common. You have an AC generator (or alternator) connected to your engine that is used to recharge and assist your battery. If the alternator is not properly electrically isolated or your radio is not well grounded, the radio will pick up these electrical emissions resulting in an annoying hum or buzz. Crutchfield has put together a pretty good guide for determining the source of your noise. You will most likely need a ground loop isolator, which you can pick up at most automotive stores for cheap.
Good luck with your project and I hope you can kill that annoying noise!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
Brilliance expresses itself in many ways–from the esoteric tinkerings of a mad genius to the profit-heavy balance sheets that illustrate the work of astute executives. Sometimes brilliance is merely a deceptively simple, why-hasn’t-anyone-thought-of-this-before solution to a nagging problem.
The products and services represented by our annual roundup of 100 Brilliant Companies are a little bit of all of these. It should come as no surprise that our list is heavy on digital technology, with apps, development platforms and gadgets related to mobile phones, social networking and health care, as well as some mind-blowing inventions that are just plain cool.
On the opposite end of the spectrum, we found much to admire in low-tech brilliance–most notably that with retro hipster appeal, as chronicled in our new-this-year category Geek Chic. Throw in a bit of fun from food, shopping, music, art and travel, and you have our list of the best ideas, the brightest innovations–and, yes, the wackiest notions dreamed up by businesses in the last year.
But brilliance is not merely subjective: In some cases, it can be quantified in dollars and cents. This is not to say that these companies are necessarily the most lucrative in their fields; few of them, if any, are that. But to get a sense of the potential value of the businesses on our list, we spoke to leading venture capitalists to find out what qualities they look for in investment targets in several of our categories. It’s a fascinating window into the minds of the people who are betting big on tomorrow’s brilliance, today.
Our hope is that, as you dip into our 10 categories, you’ll find ideas that inspire, excite and delight you–and, more than anything, perhaps galvanize you to create a bit of brilliance yourself.
I’m just getting in to the world of homebrewing my own beer. My basement is a little too cold for proper fermentation, so I’ve constructed a simple box out of foam insulation and I want to add a small heat source.
I have sensors measuring the temperature of the fermenter and the ambient air in the box. I’d like to use an Arduino to turn the heat source on and off. My plan was to buy a small space heater (Lasko My Heat ceramic heater for example), and use my Powerswitch Tail to turn it on and off. I’m worried about the life of the Powerswitch Tail, since the heater isn’t a pure resistive load (it has a small fan motor).
Should I just use a a 40-60 W incandescent bulb instead? I remember seeing an app note about how an incandescent load needs to be derated even more than an inductive load. What’s the best way to safely add a controllable heat source that won’t result in me having to replace my relay switch too often?
Mmmmmm…..theres nothing better then brewing your own and I will see if I can tackle all of your questions.
First off, you are absolutely right in questioning the type of load you are putting on your Powerswitch Tail. Lady Ada has referenced a good document that describes the different types of loads commonly connected to relays and why they can affect the overall lifespan of the relay. The document describes 5 different load types, and as you had suggested, your system would be working with either incandescent or motor+incandescent loads.
As the document describes, because the filament changes resistance based on temperature, the contacts on the relay are more prone to wear due to the high inrush current when the filament is cold. The document suggests de-rating your relay by 10% or using a series resistor to current limit the load. This would apply to both your heater and your bulb ideas and your 1800W Powerswitch Tail is now capable of safely switching 1,620W.
Your space heater also has a fan, which would be classified as a motor load (although the fan is probably pretty small). Like the inconsistent incandescent load, there is a large inrush current when starting the motor. This is usually taken care of by attaching a starting capacitor to AC motors. The result is similar to the incandescent and requires derating your relay by ~20% and your 1800W Powerswitch Tail is now capable of safely switching 1,440W….which is a little low for a space heater.
Another concern with the Powerswitch Tail as a heater control is its life expectency. Adafruit states that the Tail should be able to switch 100,000 times with a 15A resistive load. As an example, if you system constantly switches your heater on and off every 30 seconds:
30s * 100,000cycles = 3,000,000s of operation
3,000,000s / 60 / 60 / 24 = 34.7 days of operation
Depending on how long you plan on fermenting and how accurately you want to maintain temp, this might be a bit low. You might want to look at some more industrial controls or solid state relay‘s to do the job.
Also, an alternative to the lightbulb/space heater idea would be to use a silicon heater blanket. I used to work in a lab and we used these all the time to maintain temp on bio-reactors. They are much better at distributing heat then point sources like the bulb/space heater (also are a lot more safe due to their max temperature!) This, in addition to a SSR and a thermal switch, would be a pretty stable system.
I hope this has helped answer your question and good luck with your brew!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
Ember, the company known for their ZigBee system-on-chip hardware, founded by Ethernet pioneer Bob Metcalfe, will be purchased by Silicon Labs for 72 million USD. Silicon Labs, a prominent mixed-signal manufacturer, hopes to gain traction in the low-power Internet-of-Things market. More from GigaOm:
Ember has raised $81 million over its lifetime, so the $72 million price tag isn’t exactly a win. Investors in Ember have included Polaris Venture Partners, GrandBanks Capital, RRE Ventures, Vulcan Capital, DFJ ePlanet Ventures, DFJ New England, WestLB Mellon Asset Management (formerly West AM), ChevronTexaco Technology Ventures, Hitachi Corporation, Stata Venture Partners and MIT.
Silicon Labs says the acquisition will put it in a good place for the increasing “demand for low-power, small-footprint wireless technology” “as more and more IP-enabled end points are being connected to the Internet of Things.” The acquisition is expected to contribute between $10 million to $12 million to Silicon Lab’s revenue in the second half of 2012, and will be accretive on a non-GAAP basis in 2013. Ember says it has shipped 25 million units.
I’ve been hearing about a potential acquisition of Ember for months. The company has played an important role in the development of ZigBee and the Internet of Things. But as pioneers in a sector, it can be difficult to build a business off of creating building blocks for an ecosystem.
Well, this is interesting. A startup called Leap Motion has announced a new gestural controller which they claim is more accurate than the Kinect, and sells at an even lower price point ($70!). From Edgadget:
It’s about the size of a pack of gum, and once connected to your computer via USB, it creates a four-cubic-foot virtual workspace. Within that area, it tracks all ten of your fingers simultaneously to within 1/100 of a millimeter — that level of accuracy allows for rudimentary gestures like pinch-to-zoom and more complex actions like manipulating 3D-rendered objects. Naturally, the company isn’t telling much about the black magic making it happen, but Leap Motion claims that its software can be embedded in almost anything with an onboard computer, from phones to refrigerators. Users can customize it to suit their needs with custom gestures and sensitivity settings, in addition to chaining multiple Leap devices together to create a larger workspace. Plus, Leap Motion has created an SDK for devs to create Leap-compatible applications and an app discovery platform to distribute them to others. That means the Leap can work in a variety of use cases, from simply navigating your desktop to gaming and computer-aided design. The best part? Leap brings you this next-gen UX for a mere $69.99, and a select few can pre-order them now, with the full roll-out coming this winter. Full details follow in the PR below, and you can see the Leap in action in the videos after the break.
It’s nice to see them leading with an SDK — the Kinect, which was marketed originally as a game controller, did not have an SDK at launch — but I haven’t been able to figure yet what (if any) restrictions there are for developers. Hopefully, the terms will be more free than the Microsoft SDK.
Anyway, it sounds like it might be fun to play around with. Leap Motion claims the device: “creates a 3D interaction space of 4 cubic feet to precisely interact with and control software on your laptop or desktop computer.” — that’s what it was designed for, but I wonder what else you could make it do? Hmmm…
The BOE Shield-Bot is setting out to Maker Faire Bay Area 2012 to spend some time in the Maker Shed, sporting a Ping))) Ultransonic Distance Sensor and Mounting Bracket Kit to look both ways before crossing the street.
BOE Shield-Bot heading to Maker Faire, with a Ping))) Sensor for safe traveling
(1) Optional parts from Parallax for the traveling staff and bundle holder (good fit for a bamboo skewer, perfect for carrying a bundle of extra tires):
So, this is a project that was nearly a month in the making. I set out to make a sound-reactive EL panel but found that driving EL in such a way is actually kind of difficult. If you’ve been following the blog, I’ve been working on this project in one way or another since my transformers article, and it’s actually the reason I wrote that article.
Again, a disclaimer. There are over 8,000 words in this post that document all of my design decisions on this project. It is not a how-to guide, but if you have some background in EE, I hope that you gain something from it.
EL materials (wire, tape, panels) are an odd bunch. No matter where you look, EL panels seem to be always be made very cheaply and with very little documentation. There doesn’t seem to be any “pro” version of the stuff.
So my goal with this project was to try to exert more sophisticated control over EL materials. So far, everyone can seem to make EL blink fairly easily, but if I know my electronics, fancy gadgets don’t have blinking lights, they have pulsing lights that fade in and out gradually. This is usually because blinking a light is much simpler than dimming one.
So I want to make a dimming EL panel driver. And what the hell, let’s make it react to sound too.
Add a little audio-reactivity to your EL projects! Video on YouTube and Vimeo.
EL Wire 6V Sound Activated Pocket Inverter. A small, portable inverter for EL wire with an audio input! This inverter has a little microphone and will light the connected EL according to the surrounding audio volume. Makes for an easy reactive project.
This inverter requires 6V input (it works great with our 4xAA battery holder) and it can drive 2-3 meters (7 to 10 feet) of our high-brightness EL wire OR 1 meter (3 feet) of EL tape OR a 10cmx10cm piece of EL panel continuously for about 21 hours (off of 4xAAs).
There is a switch for selecting steady/sound/off modes – steady is always on. Comes with a single 2.5mm pitch female JST connectors, standard for all the EL wire and tape we carry. Theres also two power wires, youll need to connect these to a 6VDC power source.
You can plug any of our EL wire/tape into this inverter directly. To connect a raw piece EL wire to this, youll want a male connector wire
The EL inverter requires a load to stabilize itself. Do not run the inverter without at least 2 ft of EL wire attached! Otherwise the inverter can spike and damage itself
Like all inverters weve used, the 2000 Hz oscillation is slightly audible. To reduce the squeaking, we suggest opening up the case padding it with thick foam tape/weatherstripping. Squirting some hot glue around the capacitors may also help. We managed to get it silent this way.
Check out our EL TRON bag tutorial for ideas, as well as the EL wire couch video!
Soldering to raw EL wire is a little tricky but luckily we wrote a detailed step-by-step tutorial! The tutorial also covers a lot of information about EL and how it works.
July 28+29 2012, 10am – 5pm, MQ, Vienna/Austria Info and registration: office@mqw.at Location: freiraum quartier21 INTERNATIONAL
Participants will experience first hand the making of Exquisite Electronics and produce their very own piece of hand-embroidered electronic Haute Couture. The workshop will cover traditional embroidery techniques, using contemporary conductive materials, such as conductive threads, fibers, fabrics and yarns, to create highly decorative circuitry with unique functionality.
The workshop not only introduces a range of e-textile techniques, but also draws attention to issues surrounding electronic textiles, such as e-waste, diminishing resources, the industrialization of craftsmanship and the impacts of globalization. By raising these topics we hope to start a discussion among the makers of electronic textiles in order to project a more futuristic future vision of skilled craftsmanship as it may be applied to electronics. The workshop will last 2 or more days and will be open to the general public. A maximum of 15 participants will be able to attend the workshop, and while previous experience working with either textiles or electronics is encouraged, the workshop is open to everybody eager to learn and master a new set of skills.
What is the best path if you want to progress from Arduino to bare AVRs? There seems to be a range of toolchains of varying currency around so google requires a lot of digging to find if what you have is actually current. Ditto some ICSPs seem to have no windows 7 support which can be a trap if that’s your OS of choice. Another way to word the question would be ‘what is the easiest way to work with AVRs while still being able to use things like the internal oscilator and timer interupts’?
Well David, the results are in and it looks like the transition shouldn’t be too hard. It looks like AVR Studio is the way to go as far as IDE and offers debugging. You will need an AVR Dragon or the monster SKT500 for programming. As tz commented:
The AVR “Dragon” available from Digikey and other places works with the AVR studio environment as well as with avrdude (the programmer under Arduino). It can do ISP, JTAG, dW, serial or parallel high-voltage programming, I use jumpers and have added a ZIF socket
tz also wisely mentioned that because Arduino is compiled with gcc:
Any Arduino (or compatible – with the right chip and bootloader) can run pure embedded by replacing main() with init(). I just did that for my radar detector interface. You need a trivial sketch (which is never executed), but “init” is called as the first thing from the Arduino environment’s “main()”, so if you just don’t return, you can set all the registers as if you were doing a makefile and C programs. There are a few gotchas and I may not have found all cases (mainly I needed to declare things volatile if the interrupt would modify them and the main routine would read them – this is technically correct but I didn’t have to do it with the command-line direct install tools).
Bruce also nicely pointed you should take your question:
…over to avrfreaks.net. There are several very helpful and very knowledgeable AVR developers over there who could help you with this, and you’ll want to get familiar with those forums anyway as you get deeper into the mysteries of your future AVR projects. Browse the FAQs in the forum for a while and if you don’t feel like your question was fully answered, introduce yourself and ask away. Here’s a good jumping off point, I think.
Lianna has also given a quick tutorial in the 3rd comment for using an Arduino for programming non-bootloaded AVRs. This doesn’t give you the debugging capability of AVR Studio, but does offer an alternative to programming the base set of Arduino ICs.
Thanks again everyone for your feedback and wisdom, and I hope this has helped to answer your question! If anyone else has something to add feel free to leave a comment!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
[Editor's note, this is a special guest post from Darren who works with Adafruit on our badges, shirts, packaging and more! -pt]
All work and no play makes AMBRO a dull bunch, that’s why today in celebration of “The Avengers” coming out in theaters, we decided to make a cool new T-Shirt today. Most of the time that we’re using HRM “Highly Reflective Material” we’re helping to save lives and keep people safe. Firemen and Women, Police and EMS crews use reflective material on their jackets and uniforms to help keep them safe at night. The material that we use is 200+ candle power and can be seen up to 2 miles away!
Normally, we’re doing boring stuff like CAD cutting it into strips for horizontal and vertical bars to attach to vests and jackets. But not today!!! Today we cut an Arc Reactor and put it in the center of a black ladies T-Shirt. The photos that you see here have no photoshopping or special effects, there are no batteries, no wires etc … what you see is simply produced by the flash of the camera.
We’re using Micro-PrismaticReflective Material to produce this effect. Simply put, it’s a bunch of microscopic prisms all lined up on a polymer. In the photo, the picture on the far left is taken in daylight with no flash. The middle photo is taken in daylight with a flash and the picture on the far right is taken in a pitch black room with a flash.
Hopefully this will give some of you DIYers some ideas. Maybe celebrities who are looking to avoid paparazzi could have a new fashion weapon!
Thanks for letting me show my MIDI controller toy project [show-and-tell] it turned out to be a really good show! Here is a little more information about the project:
I acquired a cool used toy from my local Salvation Army some time ago for a whopping $1.95, and knew it would be a fun toy to hack. In the past I’ve experimented with using circuit bending to hack toys to make goofy noises, but this time I wanted to try to make something more useful, like a MIDI controller. In other projects I’ve used the Teensy series of microcontrollers from PJRC to mimic USB devices, and realized it could be really useful in this project. It’s cheap, powerful, small and includes native USB HID functionality, and can be used with the Arduino IDE, so it seemed like the perfect solution for me. I was able to hack together this project in a couple of days, thanks to some really helpful generalized debouncing code that Limor posted back in 2009.
This is also my first attempt at creating an Instructable, so I have tons of pictures, documentation, source code and advice about how to turn almost any rescued toy into a MIDI controller. Hopefully it will help a few of your readers create their own cheap MIDI controllers
To make the motor run forward and backwards is not a problem.
Also I am not concerned about the speed of the motor.
The H Bridge configuration is also not a problem.
But, to time the motor on and off seems not to be a regular discussion on the net.
I need to open and close a security gate simply by using a push button (like those tiny square ones always used with arduino diagrams and tutorials).
If the button is pressed momentarily, the motor needs to run one direction for e.g. five seconds and stop in its tracks and must wait for my next button press.
If I press the button again, the motor must reverse direction to its default position (same timing span ) and stop in its tracks again. So, it is purely timed on and off in either direction.
On the net are lots of code available for the control of the H bridge including the button state. But with all of those codes the motor directions are not timed. They simply forward or reverse continuously.
With my limited knowledge of coding in C (Arduino), I some how feel the delay instruction is not the way to resolve the issue (or can it be possible?), but rather to make use of the timer of the Arduino. Either options put me in the dark.
Can you advise?
Absolutely!
Rather then trying to time the Arduino to successfully open and close you gate, I would recommend using limit switches such as these. Use two, one to let the Arduino know that the gate is open, and the other to let it know the gate is closed. Then use a weatherproof pushbutton to tell the Arduino to “turn the motor CCW until the limit switch trips, indicating the gate is open” or “turn the motor CW until other limit switch trips, indicating the gate is closed.”
The other problem I see is that your security gate might run on AC rather then DC. In order for your Arduino to control the direction of an AC motor, you will need more complicated circuitry and it is considerably more dangerous. An option would be to use a AC Reversing Solid State Relay as it can be directly controlled by the microcontroller. Unless you are a trained electrician, I would NOT recommend interfacing your Arduino to an AC source.
Below is a rough schematic for your circuit and a bit of code that should get you started!
Code:
const int activate = 2; //set up our button constants
const int gateOpen = 3;
const int gateClosed = 4;
const int bridgeOneA = 5;
const int bridgeTwoA = 6;
const int enable = 7;
const int statLED = 13;
unsigned long currentTime = 0;
boolean gateState = false; //false = closed true = open
void setup() {
Serial.begin(9600);
pinMode(activate, INPUT); //set up I/O
pinMode(gateOpen, INPUT);
pinMode(gateClosed, INPUT);
pinMode(bridgeOneA, OUTPUT);
pinMode(bridgeTwoA, OUTPUT);
pinMode(enable, OUTPUT);
digitalWrite(enable, LOW); //make sure H-Bridge is off
pinMode(statLED, OUTPUT); //setup our status LED
}
void loop() {
if (digitalRead(activate) == HIGH && gateState == false) { //check to see if the button is pressed and the gate is closed
digitalWrite(enable, HIGH); //enable h-bridge
digitalWrite(bridgeOneA, HIGH); //configure for CW rotation
digitalWrite(bridgeTwoA, LOW);
while(1){ //run motor until switch is tripped
if (digitalRead(gateOpen) == LOW) { //check switch state
gateState = true;
digitalWrite(statLED, LOW); //turn off LED
digitalWrite(enable, LOW); //disable h-bridge
digitalWrite(bridgeOneA, LOW); //reset h-bridge config
break;
}
if (millis() > currentTime + 500) { //flash status LED once
digitalWrite(statLED, HIGH);
delay(500);
currentTime = millis();
}
else {
digitalWrite(statLED, LOW);
}
}
}
if (digitalRead(activate) == HIGH && gateState == true) { //check to see if the button is pressed and the gate is open
digitalWrite(enable, HIGH);
digitalWrite(bridgeOneA, LOW); //configure for CCW rotation
digitalWrite(bridgeTwoA, HIGH);
while(1){
if (digitalRead(gateOpen) == LOW) {
gateState = false;
digitalWrite(statLED, LOW);
digitalWrite(enable, LOW);
digitalWrite(bridgeTwoA, LOW);
break;
}
if (millis() > currentTime + 500) { //flash status LED once
digitalWrite(statLED, HIGH);
delay(500);
currentTime = millis();
}
else {
digitalWrite(statLED, LOW);
}
}
}
}
I haven’t tried out the code, but it should get you started in the right direction. The idea is that when the button is pressed, the Arduino configures and activates the h-bridge, moving the gate until the “open” limit switch trips and stops the motor. Then when the button is pressed again, the Arduino configures and activates the h-bridge, moving the gate until the “closed” limit switch trips and stops the motor again. There is a also small bit of code that flashes the LED during the time the motor is in motion using the mills() counter.
I hope this has helped to steer you in the right direction and good luck with your project!
Don’t forget, everyone is invited to ask a question!
“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.
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