This tiny DC motor has a shaft with an offset mass that vibrates when it rotates. Motors like this are commonly found in cell phones and other devices that use vibration for tactile feedback. The motor has 1.5″ leads and is encased in a removable rubber sleeve that gives it flat surfaces for mounting and prevents it from chattering against whatever it is mounted to. It is intended for operation around 3 V (2.4 V to 3.5 V recommended).
If you’re comfortable with wiring, soldering, heat shrink, image conversion, and are not at your first project, this tutorial is the one for you. As you’ll notice there’s a lot of expensive components used that need careful handiwork but the result is amazing.
Recently, I have been trying to gain a better understanding of how motors work. While searching the interwebs, I found a number of tutorials explaining the magnetic interactions found in motors. But many of these sites and videos failed to explain the mechanics of magnetism itself. So I dusted off my E&M book and went for it. One hour later, and my brain was fried. I had forgotten how complex Electricity and Magnetism was. Doing what any self-respecting engineer would do, I watched an unhealthy amount of YouTube. During my binge, I continued to see “Homopolar motor” and “Simplest Motor” show up. Being curious, I decided to build one and see how it worked.
As you can see, it’s about as simple as it gets: a piece of wire, magnet, and a battery. Well, how does it work? Let’s take a look!
Simply put, the Lorentz force is responsible for propelling the motor. To be more exact, it’s how the Lorentz force acts on a current-carrying wire. The resultant force is the cross product of current (along a length “l”) and the magnetic field. For our purposes, we will ignore length to keep things conceptual.
An easy way to represent the cross product is to think of the Right Hand Rule.
To re-phrase our use of the Lorentz force definition: Force is the product of current as it is orthogonal to the magnetic field. The resulting force must be orthogonal to both current and the magnetic field. What if current and the magnetic field are not perfectly perpendicular? The cross product helps us make this easy. Let’s take a simple problem:
The cross product helps us take only the parts of the field as it acts on current. In my example, “B” would represent current, and “A” would represent the magnetic field. To determine the direction of the force, you always start with your thumb along the first vector (Ay), and point your fingers in the direction of the second vector (B). The force will be in the direction your palm is facing. In our case, this is “into the page.” The circle with the “X” is supposed to look like arrow fletchings flying away. A arrow coming towards you, or “out of the page,” would have a single point.
What if I do the same problem only with C = BxA? Well, what are you waiting for? Try it! The only difference is now your thumb goes along B and your fingers along Ay. You get the same force, but reversed. This demonstrates the importance in the order we solve things. The cross product is not what mathematicians would call commutative. Now, take our example motor diagram above and reverse the current. Following the rules of the cross product and reversing the direction of current reverses the motor! Let’s take a look a one running.
(Credit and special thanks to Maurice Woods III!)
The magnetic field is created by the magnet below the battery. This is shown as red field lines traveling from the north to south pole of the magnet. Current is represented by the yellow arrows as it flows through the wire (the magnet is providing the slip ring connection to the bottom of the battery). The green arrows are showing the force created by the interaction.
Well that was cool! What happens when you lay it out flat? You get a linear homopolar motor!!!
Same rules apply F=IxB.
Building one is simple. You just need some form of rails, magnets, and a non-ferrous conductive rod/tube. I found that model rail track was easy to get. I grabbed a box of magnets from inventory, and the copper tube was something I found at the hardware store. Finally, I laser cut some plastic to help me hold it all together. It’s important to glue all the magnets in the same orientation or the rod will not continue down the track. This can be done by marking them or checking polarity as you assemble. Special thanks to Riley H. for helping me glue all these magnets together!
Powering it with a current limited DC supply is suggested. We used 5 amps in the video
Assembly view showing magnet orientation
What if we crank up the current? Thanks for asking! Well, for starters, things get hot. So hot that when we add say, 5 million amps, things start to turn to plasma.
The need for an external magnetic field is also removed. Passing current through a wire creates its own magnetic field. This is governed by Ampère’s circuital law. We’ll save that topic for a later date. Now, how is this useful? There are plans to use systems like this to put satellites into orbit without burning rocket fuel. Time will tell if it works out!
This was a great tangent I took while writing the new Motor Tutorial. I learned a lot about magnetism, and it really solidified my understanding of the subject. Check it out and see how some of these concepts are put into the context of a motor you might actually use.
If you were one of the people following us on Twitter a couple of Saturdays ago, when we all hoofed it up to Manchester for the Manchester Raspberry Jam, you’ll have had a sneak preview of this: Dr Andrew “Pi Face” Robinson’s latest Pi escapade. I’ll let Andrew explain what’s going on. (Notice the mildly humiliating guest appearances from me and Clive.)
We think this is one of the most interesting photographic applications we’ve seen in the flesh so far. (Although I will admit to a moment’s disappointment when, on seeing it, getting excited and asking what it did, I was told that it was not a working Stargate after all.) You’ll have read many posts here about bringing down the price of professional photography equipment: we’ve seen focus-stacking on a budget, gigapixel photography, setting up moving time-lapse rigs, and shooting water droplets along with many, many other applications. (The photography tag here is one of my favourites – if you’ve got a few minutes, go and have a read.)
Andrew’s Frozen Pi setup shows us yet another example of bringing photographic technology with an astronomical off-the-shelf price down to achievable levels: of course, with 48 Raspberry Pis this still works out pretty pricey, but it means that any school with a classroom set of Pis suddenly finds it has bullet-time effects photography well within its grasp.
Which is just brilliant, isn’t it? Thanks Andrew!
When we decided to open our Greenwich and Boston MakerBot® Retail Stores, we knew we needed to fill them with some amazing 3D printed things. So we carefully handpicked some our favorite 3D prints for the forward-thinking creators, explorers, and 3D modelers who are discovering and embracing the power of desktop 3D printing.
Scissor Hands: This pair of Scissor Hands extends beyond your reach, making it the perfect super-powered gift for the multitasking entrepreneur.
iPhone Amplifiers: Supercharge your phone’s sonic powers without using a single battery. Bring your iPhone by the store and take our acoustic iPhone Amplifiers for a spin.
Holiday Ornaments: Multiple color options and a lovely diamond motif make these ornaments a must-have for a creative friend or family member.
Great holiday gift ideas aren’t the only thing drawing folks to the MakerBot Retail Stores this December. We’ll be offering exciting deals and giveaways at all MakerBot Retail Stores from now until the end of the year, including the opportunity to win a free MakerBot® Replicator® 2 Desktop 3D Printer.
Thingiverse Meetup in Boston
We’ll also be holding a Thingiverse meetup at our Boston location at 144 Newbury Street tomorrow, Thursday, December 12th, from 7-8:30 p.m. Join your fellow Thingiverse community members for cookies and 3D printing conversation. We’re even giving away a free spool of MakerBot® PLA Filament to the first ten Thingiverse community members who show up.
In 2005, Shop.org supposedly coined the term Cyber Monday for, in their view, the biggest online shopping day of the year. At present occurring mainly in the U.S. and Canada, this is a weird time of year where both stores and people binge on capitalism. Traditionally, big markdowns and stampeding are the scene at brick and mortar stores on Black Friday immediately following Thanksgiving. Big markdowns and increased mouseclickery now follow the next Monday.
Like all internet things, it’s quaint to see skeptics exhort us not to believe the myth of Cyber Monday through the sharp lens of hindsight. But in 2013 it’s become a given that online retailers do something for Cyber Monday. Or at least that’s how it feels now that we’ve done two, and everybody seems to win.
Last year we first attempted Free Shipping all day, and even that looks a bit outdated, now that we have Free Shipping all the time. At the time it was a new direction, though, and resulted in our biggest sales week of the year! We learned that Cyber Monday can be a big deal for the SparkFun community too, and we got to test-drive a free shipping program.
As an aside, because of all our awesome SparkFun customers, free shipping $60 and up has been working out swell. Many of you have told us how it has changed your shopping habits for the better and, so far, it’s been affordable on our end. It’ll eventually change (as all things do) but for now it’s here to stay.
We had just shy of 4,000 orders on December 2nd. This is akin to a week’s worth of orders on one day! A huge thank you goes out to all of you in the SparkFun community that showed up and made that happen. Also, hats off to our shipping crew that needed the rest of the week to get everything packed and shipped. Customer Service had over double the number of calls, emails, and chats for a typical Monday. Site traffic only saw about a 25% increase, which is rather paltry considering some past events that saw increases by an order of magnitude. Regardless, daily site traffic these days is just higher than it used to be, and altogether last week ended up as our biggest site traffic week ever, just edging out the week of Free Day 2012.
Looking at products, we saw some interesting stories play out. The Makey Makey Standard Kit, retailing for $49.95, spent the entire day at just over $30, even dipping just below from 10AM-11AM. A quarter of the 72 orders for it got two or more, many to hit that $60 free shipping mark. The biggest seller by volume was easily Arduino Pro Mini 328 - 5V/16MHz with 1008 sold (straight break away headers, likely for all those Pro Minis, came in second with 679 sold and they weren’t on sale).
Then there’s the Mr. Roboto Kit. Enjoying a 40% flash sale from 2PM - 3PM, and 20% all day sold 24 units of this little guy. Out of context, big whoop, but considering Mr. Roboto usually sells only 1.7 units a week, that’s over 14 weeks of sales in one day! It actually saved this little kit that could from early retirement.
No Cyber Monday retrospective would be complete without mentioning our Distributors. Before all the goodies were rolled out to customers on December 2nd, we ran a 72-hour sale on SparkFun Originals for all the distros. It’s an apples-to-oranges comparison with the Cyber Monday everyone saw, since distributors do business with SparkFun under a different set of rules, but it helped all of them stock up and run their own sales in concert with us on Cyber Monday. A big thank you goes to our distributors who got in on the action and stocked up! And for you international customers, please take a look at the Distributors Page sometime to see if any are in your area!
So what’s next? First there’s next week’s Christmas Candy Pro Mini Giveaway. Aside from that, there are many ideas floating about. To make Cyber Monday possible we built a new tool for dynamic scheduled pricing and it’s already getting version 2 built out before year’s end. It consolidates pricing logic across SparkFun.com (which, given years of organic growth, has led to a contained but messy ball of mud), allowing us to get creative and do more sales in the future.
As you all have graciously responded so well to events like this, we want to keep doing them, but we also want to keep them fresh and interesting. One hotly debated topic is whether you enjoyed the relative complexity of Cyber Monday or would prefer more simplicity. There was the ability, for those that did their homework, to stack discounts and free shipping together to get the feeling they were robbing SparkFun (we survived overall so I think this was a win-win situation). Which do you prefer?
Clearly we’ll doing another Cyber Monday something next year. It is still a culturally limited affair, however. Not everyone does the Thanksgiving+Christmas 1-2 punch. Are there big shopping days in your corner of the globe when you would like to see us running special events?
And, assuming we do more sales year-round, what would you like to see us do?
There once was an honest shoemaker. You might even find this shoemaker too honest if you ever kissed him, because he makes shoes inspired by former lovers. The Heartbreaker has an arrow through the back. The Boss has brass knuckles underneath and a true stiletto heel. The heel of the Jetsetter is an airplane. On the Gold Digger, it’s a classical figure like Atlas, holding up the woman who would wear it.
The shoemaker made 12 shoes for 12 lovers on his MakerBot Replicator 2X Experimental 3D Printer. Then he sanded, primed, and painted them, and brought them to Miami Beach for Art Basel, the international art fair. But you can’t walk away in the Boss or the Jetsetter just yet, since he’s only made one of each.
Shoemaker, Designer, Artist
The shoemaker’s name is Sebastian Errazuriz. He straddles the worlds of design and fine art. Before he made shoes, Errazuriz pastured a live cow on the roof of a skyscraper, created a wooden cabinet inspired by a porcupine, and planted a tree in the middle of the National Stadium in Santiago, Chile. Errazuriz grew up in Chile but now works in Brooklyn, NY, in an airy studio a few blocks north of the MakerBot factory.
At the Studio
We visited Errazuriz’s studio as he was preparing “12 Shoes for 12 Lovers.” The MakerBot Replicator 2X finds itself in the company of much larger machines for carving wood and milling metal, as well as a wall full of hand tools. But as Errazuriz says in the video, a 3D printer, like any tool, is a means to an end. “At the end of the day it all goes back to ideas: What do you want to say? What do you want to contribute? What do you want to solve?”
Even Errazuriz cannot expect to solve the age-old mystery of how men and women get along. But he joins a long line of artists who try to make sense of their relationships, whether on a canvas, in bronze, or, now, in a 3D printed shoe.
You can see the shoes at the Melissa pop-up shop in Miami Beach through January 6.
The results are in! Thanks to everyone who entered the more than 250 fantastic ornaments in our Thingiverse Ornament Challenge.
We teamed up with the Peabody Award-winning public radio show Studio 360, hosted by cultural critic and author Kurt Andersen and produced by WNYC and PRI, to co-sponsor the challenge. All our winners will receive one spool of a MakerBot PLA filament and a Thingiverse t-shirt and have their designs featured on Thingiverse over the next ten days and in each of our MakerBot stores.
One Grand Prize Winner
Find out who won grand prize by watching a live video webcast of “Science Fair: Studio 360 in 3D,” a special event hosted by Kurt Andersen at The Jerome L. Greene Performance Space at WNYC in SoHo on December 17th at 7pm ET. Our winner will join MakerBot CEO Bre Pettis as a guest on the show.
In the meantime, come see our ten winning prints displayed at our three MakerBot Retail Stores:
- NYC: 298 Mulberry Street
- Boston: 144 Newbury Street
- Greenwich, CT: 72 Greenwich Avenue
Blizzard of Customizable, Mailable Snowflake Ornaments by laird
Print out a gigantic variety of unique snowflake ornaments using this customizable design. Choose a number up to 99999999 and see what pattern your snowflake will be! Print a flat one or assemble three together into a snowflake orb.
Lockable Present Ornament by jijimath
Lock away little presents until Christmas morning in this fabulous little gift box. The locking device prints and assembles easily. Hide the key until it’s time to open presents!
Snowflake Bauble by MakeALot
Each time you customize this ornament, the script generates eight random snowflakes. Print in MakerBot Translucent PLA Filament with only two shells and 0% infill for a sparkly holiday treat!
Snowflake Icosahedron Ornament by pdragy
Inspired by “ITSPHUN shapes (itsphun.com) and Mother Nature,” these 3D modular geometric snowflake orbs use clean, simple notches to hold the delicate, individually-printed snowflakes together.
Spiral Sphere Ornament by kowomike
This customizable ornament design allows you to choose the size of your orb, the number of spiral “ribbons” decorating it, and whether you want one or two helixes running in different directions around it.
A week from today (that’s December 18th, 2013), we are giving away delicious Christmas candy. Well, our version of Christmas candy (and it might not be delicious - in fact, we don’t recommend eating it).
Behold, the Limited Edition Christmas Candy Arduino Pro Mini:
The details are pretty simple - on December 18th only, starting at 9 a.m Mountain Time, we’ll be putting one of our Limited Edition 5V Pro Minis in the first 700 orders over $50 (not including shipping/tax) for free!
We’ll be putting the Pro Minis in qualifying orders until we run out - that could be a few hours, it could be a few minutes, it could last the whole day. So join us on December 18th and get one while supplies last!
We first met Shea Silverman, based down in Florida, on one of our 2012 hackspace tours when we first visited FamiLAB. Shea’s brilliant – he does a lot of work with the Pi and MAME (the Multiple Arcade Machine Emulator), and he made us a really cute little Pi arcade cabinet which we display in the office. We’ve stayed in touch, and he’s let us know about the projects he’s been working on in that time; most recently Shea has written a book called Instant Raspberry Pi Gaming for absolute beginners who want to start gaming with the Raspberry Pi. (Thanks for the copy with the inscription, Shea!)
The book shows you how to set up software like MAME, SNES, Atari 2600 and PlayStation emulators; and how to keep them up to date. If you’re a gamer who wants to get started with a Pi, or someone who’s interested in retro gaming, it’s a great place to begin.
Shea’s blog is another great resource for Raspberry Pi users, with a particular emphasis on games, emulation and embedded systems. Recently, we’ve seen more and more people wanting to add a start-up video to their Pi, and Shea’s noticed the same thing, and has blogged his solution, which is rather neat.
This is Shea’s bootsplash animation for his PiMAME system, running on a Pi-enabled Motorola Lapdock. He’s using OMXPlayer to play a video file while the Pi itself is booting.
You can use any video you choose – it needs to be around 20 seconds long so it runs for long enough to cover up the scrolling kernel messages that you usually see during the Pi’s boot sequence. Shea walks you through the very simple startup script you’ll need, and through installing your video, on his blog. It should take you all of five minutes to set up.
Thanks, as always, for all your work on the Pi, and on your book, Shea. The Raspberry Pi depends on community members like you and the amazing amounts of effort you put in: we couldn’t do it without you and the thousands of other people that make the ecosystem around our little device so rich and interesting.
This compact breakout board makes it easy to use Allegro’s A4990 dual motor driver, which can control two bidirectional DC motors over a wide operating voltage range of 6 to 32 V. It is capable of delivering a continuous 0.7 A to each motor channel, and onboard sense resistors enable the A4990 to limit the peak motor current to about 0.9 A per channel. The driver also features protection against reverse-voltage, under-voltage, over-voltage, over-current, and over-temperature.
This powerful boost regulator efficiently boosts input voltages as low as 2.9 V to a higher, adjustable output voltage between 9 V and 30 V while allowing an input current as high as 5 A.