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ถูกปรับปรุง 3 hours 40 min ก่อน

Amazon Dash Button Finds Your Phone

6 hours 10 minก่อน

This scene replays quite often in our house: my wife has misplaced her cell phone so she asks me to call her. But where did I leave my cell phone? And the race is on! Who will find their phone first to call the other?

[Zapta] solves this problem with his Phone Finder. The system comes in two parts: a base station with WiFi that’s also connected to the house’s phone line, and an arbitrary number of Amazon Dash buttons that trigger dialing commands.

[Zapta] presses a Dash button, which connects over WiFi to the base station. The base station recognizes the MAC address of the button, looks up and dials the corresponding missing cell phone. This solves the need-a-phone-to-find-a-phone problem very neatly, and since Dash buttons are dirt cheap they can be scattered liberally around the house. They’re clearly marked “his” and “hers” suggesting a similar domestic dynamic.

If we were implementing the base station from scratch, we’d probably try to figure out how a single ESP8266 could do all of the heavy lifting, but browsing through [Zapta]’s GitHub and the included circuit diagram (PDF) demystifies the phone-line interface.

In the early days of cordless phones, we used to joke that a solution to losing them would be to attach a string and tie them to the wall. (Luddites!) We’re glad to see [Zapta] take this project in the opposite direction — using technological overkill to solve the unintended problems that arise from technological progress.


Filed under: Cellphone Hacks

Hackaday Prize Entry: Coffee Machine Grows In Complexity With No Sign Of Stopping

9 hours 9 minก่อน

In Star Trek, there is a race of cyborgs with a drive to slowly assimilate all sentient life. Their aesthetic is not far off from the one [Ronald]’s ever expanding coffee machine is taking on. One has to wonder, what dark purpose would bring the Borg into existence? Where did they start? If [Ronald] doesn’t get a satisfying cup of coffee soon, we may find out.

We covered the first iteration of his brewing machine in 2013. We like to imagine that he’s spent many sleepless, heavily caffeinated days and nights since then to arrive at version 2. This version is a mechanical improvement over his original Rube Goldberg contraption. On top of that, it has improved electronics and code, with a color screen reminiscent of industrial control panels.

He’s also working on something called, “AutoBaristaScript(TM),” which attempts to hold the entire universe of pour-over coffee within its clutches. We don’t know when he’ll stop, but when he does finally create that perfect cup, what’s left of the world will breathe easier. They’ll also drink good coffee.

The HackadayPrize2016 is Sponsored by:

 

Editor’s Note: The Borg do not necessarily want to assimilate all sentient life as an end unto itself. The Kazon were deemed unworthy of assimilation (VOY: Mortal Coil). The Borg are driven towards perfection, accomplished by adding technological and biological distinctiveness to their own.


Filed under: cooking hacks, home hacks, robots hacks

Pan and Tilt with Dual Controllers

12 hours 11 minก่อน

It wasn’t long ago that faced with a controller project, you might shop for something with just the right features and try to minimize the cost. These days, if you are just doing a one-off, it might be just as easy to throw commodity hardware at it. After all, a Raspberry Pi costs less than a nice meal and it is more powerful than a full PC would have been not long ago.

When [Joe Coburn] wanted to make a pan and tilt webcam he didn’t try to find a minimal configuration. He just threw a Raspberry Pi in for interfacing to the Internet and an Arduino in to control two RC servo motors. A zip tie holds the servos together and potentially the web cam, too.

You can see the result in the video below. It is a simple matter to set up the camera with the Pi, send some commands to the Arduino and hook up to the Internet.

The serial protocol for the Arduino is simple: The Pi sends a numeric position followed by a P (for pan) or T (for tilt) at 9600 baud. A web server and some Python handle the interface to the Internet and the human.

We’ve certainly seen our share of similar projects. Some of them have been a bit larger.


Filed under: Arduino Hacks, Raspberry Pi

High-end Headphones Fixed with High-end CNC Machine

15 hours 11 minก่อน

Warranty? We don’t need no stinking warranty! We’re hackers, and if you have access to a multi-million dollar CNC machine and 3D CAM software, you mill your own headphone replacement parts rather than accept a free handout from a manufacturer.

The headphones in question, Grado SR325s, are hand-built, high-end audiophile headphones, but [Huibert van Egmond] found that the gimbal holding the cups to the headband were loosening and falling out. He replicated the design of the original gimbal in CAM, generated the numeric code, and let his enormous Bridgeport milling machine loose on a big block of aluminum. The part was drilled and tapped on a small knee-mill, cut free from the backing material on a lathe, and bead-blasted to remove milling marks. A quick coat of spray paint – we’d have preferred powder coating or anodization – and the part was ready to go back on the headphones.

Sure, it’s overkill, but when you’ve got the tools, why not? And even a DIY CNC router could probably turn out a part like this – a lot slower, to be sure, but it’s still plausible.


Filed under: misc hacks

Tricking Duck Hunt to See A Modern LCD TV as CRT

18 hours 10 minก่อน

A must-have peripheral for games consoles of the 1980s and 1990s was the light gun. A lens and photo cell mounted in a gun-like plastic case, the console could calculate where on the screen it was pointing when its trigger was pressed by flashing the screen white and sensing the timing at which the on-screen flying spot triggered the photo cell.

Unfortunately light gun games hail from the era of CRT TVs, they do not work with modern LCDs as my colleague [Will Sweatman] eloquently illustrated late last year. Whereas a CRT displayed the dot on its screen in perfect synchronization with the console output, an LCD captures a whole frame, processes it and displays it in one go. All timing is lost, and the console can no longer sense position.

[Charlie] has attacked this problem with some more recent technology and a bit of lateral thinking, and has successfully brought light gun games back to life. He senses where the gun is pointing using a Wiimote with its sensor bar on top of the TV through a Raspberry Pi, and feeds the positional information to an Arduino. He then takes the video signal from the console and strips out its sync pulses which also go to the Arduino. Knowing both position and timing, the Arduino can then flash a white LED stuck to the end of the light gun barrel at the exact moment that part of the CRT would have been lit up, and as far as the game is concerned it has received the input it is expecting.

He explains the timing problem and his solution in the video below the break. He then shows us gameplay on a wide variety of consoles from the era using the device. More information and his code can be found on his GitHub repository.

We’ve featured [Charlie]’s work in the retro gaming field before, with his HDMI mod for a Neo Geo MVS. Console light guns have made a lot of appearances on these pages, a recent one was this video synthesiser but it’s this burning laser mod that most children of the 1980s would have given anything to own.


Filed under: nintendo hacks, nintendo wii hacks

Four Of Our Favorite Hardware Talks

19 hours 40 minก่อน

The Hackaday SuperConference is the greatest gathering of hardware hackers on the planet. Last year at the SuperCon, we saw talks on building systems from scratch, creating new and interesting uses for technology, and bringing those electronic bits to market. What are we talking about? Here are four of the best talks from last year’s Hackaday SuperConference:

[Shanni Prutchi] is an ECE student at Rowan University, and has already published papers on radio astronomy and metrology. Her provides an overview of building her own source of quantum entangled photons and how these photons can be used. Quantum Key Distribution is possible on a small-scale, and not just in the realm of university optics labs.

The best conference talk I’ve ever seen came from [sprite_tm] last year. He created a Matrix of Tamagotchis. Tamagotchis — those loveable digital pets living in an embedded system — are really just computer code, after all, and after reverse engineering the Tamagotchi itself, he emulated several on a server, giving them the ability to communicate with each other and even have children. The best part? [sprite]’s Matrix isn’t a weird almost-perpetual motion machine demanded by studio execs.

Building one of something is easy, but building a thousand is a million times harder. This is the problem of manufacturing electronics, and no one covered it better than [Zach Fredin] and his talk on pilot scale production. The first step of manufacturing is always the hardest, and for [Zach] that was pilot scale production. In the talk, [Zack] gave a few tips like always springing for a stencil, where to get boards manufactured, and the ins and outs of EDA software.

Haptic interfaces are the next frontier. Eventually, we’re all going to be wearing our computers, and [Neil Movva]’s talk on haptic technology was the state of the art in interfaces based on touch. He had some hardware to demo at the conference, demonstrating how different vibrations can feel like different textures. It’s weird, and at the forefront of technology.

We Want You To Speak At This Year’s Supercon

These are just a few examples of the best talks from last year’s Superconference. They’re the cream of the crop, but it’s a new year and we’re looking for the latest and greatest from the Hackaday community. We know we have the most technically literate, adept, and knowledgeable hardware community out there, and we want to showcase that knowledge. Send in your proposal now and share your knowledge with the Hackaday community.

The 2016 Hackaday Superconference is happening on November 5th and 6th, in Pasadena, California. View all the talks from 2015, get excited, and get your proposal submitted!


Filed under: cons, Hackaday Columns, roundup

Shell Game

21 hours 9 minก่อน

A lot of us spend a lot of time switching between Windows and Linux. Now that platforms like the Raspberry Pi are popular, that number is probably increasing every day. While I run Linux on nearly everything I own (with the exception of a laptop), my work computers mostly run Windows. The laptop is on Windows, too, because I got tired of trying to get all the fancy rotation sensors and pen features working properly under Linux.

What I hate most about Windows is how hard is it to see what’s going on under the hood. My HP laptop works with a cheap Dell active stylus. Sort of. It is great except around the screen edges where it goes wild. Calibration never works. On Linux, I could drill down to the lowest levels of the OS if I were so inclined. With Windows, it is just tough.

War is Shell

One place where Linux always used to have an advantage over DOS and Windows was the shell. There are lots of variations available under Linux, but bash seems to be the current pick for most people. If you want more power, you can move to some alternatives, but even bash is pretty powerful if you learn how to use it and have the right external programs (if you don’t believe it, check out this web server).

In the old DOS days, some of us went to 4DOS which was nice, but no bash (and apparently morphed into the Windows Take Command Console software. I’ve seen a few people use things like Rexx as a shell under DOS or Windows, but it has always been a small minority.

Windows Power

Microsoft finally addressed the shortcomings of its default command interpreter, first introducing Windows Scripting Host to allow Javascript and VBScript batch files. Eventually, this was supplanted by Monad which later became known as the Windows PowerShell.

In addition to running programs, the PowerShell can use functions and cmdlets (programs made to interact with the shell). While it isn’t compatible with a traditional Linux shell, it has similar powers and many people–especially system administrators–make heavy use of it to automate tasks.

Shell Shock

Two things have recently happened that surprised me. First, Microsoft made bash available (and other Linux executables) for Windows 10 as a native application (you can find the detailed install directions online). The surprise isn’t that this is possible. I’ve used Cygwin and UWIN to have a very full-featured Linux environment under Windows for years (and did the same with MKS under DOS). The surprise was that Microsoft would “cross the streams” and officially support a Linux/Unix tool on Windows. Sure, NT used to have a crippled POSIX subsystem, but it wasn’t practical. This appears to be a genuine attempt to put the shell on Windows (which, again, is only remarkable because it is Microsoft doing it).

The second piece of news that surprised me is that you can now get PowerShell for Linux or OS/X. I’m not sure how many Linux users will rush out for a .NET tool, but it is one more way to make the systems more alike which is nice when you use both.

Decisions, Decisions…

So now you have several options for using Linux and Windows without going crazy switching between the two:

  • Run Linux and put Windows in a virtual machine
  • Run Windows and put Linux in a virtual machine
  • Use bash everywhere (using Cygwin or the Microsoft product)
  • Use PowerShell everywhere

If you just can’t stand to take software from Microsoft, you could check out PASH, which is essentially a rewrite of PowerShell using Mono. I’m not sure how much momentum it will retain now that Microsoft is supporting something so similar.

If you do want to learn more about PowerShell, the Wikipedia article on it has a nice table that relates PowerShell to cmd.exe to Linux shell. There’s also a video, you can watch below.

Thanks to [rogeorge] for the tip about PowerShell.


Filed under: Hackaday Columns, rants

Citizen Scientist Radio Astronomy (and More): No Hardware Required

อังคาร, 08/30/2016 - 22:30

We sometimes look back fondly on the old days where you could–it seems–pretty easily invent or discover something new. It probably didn’t seem so easy then, but there was a time when working out how to make a voltage divider or a capacitor was a big deal. Today–with a few notable exceptions–big discoveries require big science and big equipment and, of course, big budgets. This probably isn’t unique to our field, either. After all, [Clyde Tombaugh] discovered Pluto with a 13-inch telescope. But that was in 1930. Today, it would be fairly hard to find something new with a telescope of that size.

However, there are ways you can contribute to large-scale research. It is old news that projects let you share your computers with SETI and protein folding experiments. But that isn’t as satisfying as doing something personally. That’s where Zooniverse comes in. They host a variety of scientific projects that collect lots of data and they need the best computers in the world to crunch the data. In case you haven’t noticed, the best computers in the world are still human brains (at least, for the moment).

Their latest project is Radio Meteor Zoo. The data source for this project is BRAMS (Belgian Radio Meteor Stations). The network produces a huge amount of readings every day showing meteor echoes. Detecting shapes and trends in the data is a difficult task for computers, especially during peak activity such as during meteor showers. However, it is easy enough for humans.

There are many other Zooniverse projects if that one doesn’t fit your fancy. You can search for comets and supernova, study animal behavior, help transcribe documents from Shakespeare’s contemporaries, or study weather patterns from old ship’s logs. You won’t get paid (or charged, either) but you’ll be helping science and maybe learn something, too. The typical project gives you some form of training and relies on many people evaluating the same data to ensure the quality of the results is good.

You can find a video about an older Zooniverse project, below. In that one, you classify shapes of distant galaxies. Don’t get us wrong, though. There’s still independent citizen scientists out there. We have even covered a few of the more notable specimens. These are great projects to spur the interest of a budding young scientist, or rekindle the scientific spirit in us old timers. Would probably make a fair classroom project, too.


Filed under: news

Review: Monoprice Maker Ultimate 3D Printer

อังคาร, 08/30/2016 - 21:00

A few months ago, a very inexpensive 3D printer appeared on Monoprice. My curiosity for this printer was worth more than $200, so I picked one of these machines up. The Monoprice MP Select Mini is an awesome 3D printer. It’s the perfect printer to buy for a 13-year-old who might be going through a ‘3D printing phase’. It’s a great printer to print a better printer on. This printer is a sign the 3D printing industry is not collapsing, despite Makerbot, and foreshadows the coming age of consumer 3D printers.

The MP Select Mini isn’t Monoprice’s only 3D printer; the printer I bought was merely the ‘good’ printer in the good-better-best lineup. Since my review of the MP Select Mini, Monoprice has introduced their top of the line, the Maker Ultimate 3D printer. Monoprice asked if I would like to take a look at this offering, and I’m more than happy to oblige.

After a week of burn-in, I can safely say you’re not wasting your money on this $700 3D printer. It’s not a starter printer — it’s one that will last you a long time. 2016 is the beginning of the age of consumer 3D printers, and the Monoprice Maker Ultimate is more than proof of this.

Yes, It’s A Rebadge One feature missing from the Monoprice version is the acrylic side panels and top. If you have a laser cutter, these can be easily fabricated. Image source: wanhaousa.com.

The Monoprice Maker Ultimate is a rebadge of the Wanhao Duplicator 6, and should be regarded as the same exact printer. The Monoprice sells for $700, whereas the Wanhao sells for $800, but the Monoprice does not come with acrylic panels for the sides and top of the printer. Other than that small difference, you’re looking at the same printer. Whether the addition of acrylic enclosure panels is worth the $100 markup depends on the user. Anyone with access to a laser cutter could easily make a replacement for these panels, and I eagerly look forward to those .DXF files appearing online shortly.

The fact that this is a rebadge of a Wanhao printer is a selling point. Wanhao has a rather large following because of their version of the i3, and with that following comes the availability of spare parts. My review of the low-end Monoprice printer, the MP Select Mini, lamented the fact that no spare parts were sold by Monoprice, and no distributor for the original manufacturer could be found in the US. At the very least, you can get parts for the Monoprice Maker Ultimate from the US distributor of Wanhao printers. This printer is also slightly more standardized than the built-to-a-price MP Select Mini, and replacement nozzles and hotends are available through the usual online retailers.

Specs, Construction, and Impressions

Let’s get one thing out of the way right now. This is an Ultimaker clone. The software menus for the OLED control panel are exactly what you would find on an Ultimaker. The mechanical setup for the X and Y axes are almost Ultimaker, except there are two cross-bars on the carriage instead of one. The Z axis is exactly the same, except the two ‘corner’ bed adjustment points are in the back, not the front. The only significant difference between the Monoprice Maker Ultimate and an Ultimaker is the extruder on the XY carriage. The Ultimaker uses a Bowden setup, whereas the Monoprice stacks a stepper and a direct drive extruder on the carriage. That’s it. That’s the only difference. With the extruder on the carriage, the top speed of this printer is theoretically lower than the Ultimaker, but I haven’t noticed any issues.

The enclosure for this printer is exceptionally solid. The front, top, and side of the printer are a single sheet of aluminum. The sides are welded on to this sheet, and all the components are attached to this very strong, very robust frame. The powder coat finish will hold up reasonably well. This printer is all about mass, and this design choice continues to the 1/4″ thick aluminum build plate. This aluminum build plate heats up fast compared to my 6″ square Printrbot Metal Simple, and all the electrical connections are solidly crimped and covered with heat shrink.

While I’ve only used this printer for about 130 hours in the week or so I’ve been using it, that is much more time per 3D printer review than I’ve seen at other usual outlets. It’s not accurate to say a week or so or run time is enough to properly assess a printer. For that, I would need months of print time, I’d need the nozzle to clog, and with any luck a few bearings would give out. I pushed this thing hard, though, grinded some ABS in the extruder, and put a few nice, deep marks in the replaceable build surface. I have come away with the impression this is a very robust 3D printer. It can handle daily use in a workshop and daily abuse in a classroom. It’s built to last, and I don’t see this printer going out of commission anytime soon.

The specs — as given in the manual, not the online spec sheet — list the build volume as 200 x 200 x 175mm. The position precision in the X and Y axes are 12.5 micron, in the Z is 5 micron.  This is a printer built for 1.75mm filament, and comes equipped with a 0.4mm nozzle. Print speed is listed as 1- 300 mm/s, travel speed is 1-350mm/s. The printer weighs thirty pounds.

Sample Prints, Print Quality, and Capabilities

During testing, I only used the stock settings on the printer (changeable through the OLED display), and the suggested settings for Cura. These settings are more than sufficient to produce excellent quality prints, although I did have issues with stringing on retraction. That issue is easily cured with a bit of fiddling with the retraction settings in the slicer and by setting the temperature a bit lower.

Sappho’s Head printed at 0.02mm layer height. Click to embiggen

For years now, the highest quality prints have always seemed to come out of an Ultimaker, and since this printer is effectively a clone of the Ultimaker, there’s a certain expectation I had in testing. I was not disappointed.

I believe machines that only move the bed in the Z direction invariably produce higher quality prints. Extremely well-tuned i3-style printers are the exception to this rule, but the Monoprice Maker Ultimate is what I would expect in this regard: very high-quality when printing at very small layer height.

Unlike the $200 Monoprice MP Select Mini, there was no Z-banding to speak of. The trapezoidal Z axis leadscrew was more than capable of moving the bed down to exactly where it needed to be, and the Ultimaker-style cartesian arrangement had very little slop in it.

This does not mean the printer is without its faults, though. One glaring oversight can be found in the fan used to blow air onto the freshly extruded plastic. There’s one problem with this fan: it doesn’t blow air onto freshly extruded plastic. Instead, it blows air a few centimeters to the right of the print.

The part cooling fan blows straight down, and does not actually cool the filament as it is extruded.

The best example I can come up with to demonstrate this filament-cooling problem is an overhang, and the Benchy tugboat I printed provides more than enough evidence that overhangs will be a problem with this printer. The duct for the part cooling fan can be taken off easily, and once I tear down this machine a bit more, I’ll start work on designing a better low-profile duct that blows air a little closer to the nozzle.

Aside from a problem with overhangs, this really is a printer with remarkable build quality. All sample prints were dimensionally accurate, the bow of the 3D Benchy was one of the best I’ve ever seen, and even the name on the back of this little tugboat was readable. Apart from an issue with retraction — a function of tuning, and one that is fixable with the right settings — I can easily see the potential for this printer to produce Ultimaker-quality prints.

As far as the bed is concerned, it’s acceptable, despite the limited information available on the build surface. The bed is aluminum, heated by a 24V PCB. It comes up to temperature quickly. This printer ships with an ‘adhesive sheet’, and the only data on what this build surface actually is comes from the Wanhao product description: it’s a “Wanhao Adhesive Sheet”. That’s not a lot of information, but it seems to be a perfectly acceptable build surface. ABS, PLA, PETG, and Ninjaflex sticks to the bed and the prints are easy to remove.

I’m a believer in a PEI build surface. It’s the build surface of the future, and the build surface I’ll eventually slap on this printer. That’s not to knock the ‘adhesive sheet’ that ships with this printer — it’s acceptable, even if it is a pain to remove. My advice, though, would be to ignore the spare build sheet included with this printer and spend $16 on a PEI sheet.

A Word On Speed And Acceleration

In the review for the Monoprice MP Select Mini, I called out Monoprice for not knowing what they were selling. In that particular case, it wasn’t a bad thing — the printer was better than what their spec sheet said. It could print at a much lower layer height than the stated 100 microns, and the product copy makes no mention of the ARM controller board. The MP Select Mini was undersold, which can only be the result of two mutually exclusive truths. Either Monoprice wants to undersell their cheapest printer to bump potential buyers up to the next best printer in their lineup, or Monoprice doesn’t have the institutional knowledge needed to properly assess or write copy for 3D printers.

Now, with two data points, it’s a little more clear which truth is more likely.

Push filament out of the nozzle too fast, and you’re going to grind some filament.

The online spec sheet for this printer says the printing speed of Monoprice Maker Ultimate printer is 150 mm/sec. This is fast, but comparable to a very well-tuned Ultimaker. The specs for this printer found in the product manual, however, list the top print speed as 300 mm/sec and the top travel speed of 350 mm/sec. This is a bit high.

Just to test things, I tried printing at 300 mm/sec. At this speed, and at a 0.1mm layer height, the nozzle is squirting plastic out at a rate of 12mm³/sec. This volume of plastic per second would be too much for a 12V heater, but the 24V hotend performed admirably — until the extruder started stripping filament, of course. You simply can’t push plastic out of a nozzle that fast, no matter what a spec sheet says. It may have worked at a lower layer height, but that brings us to another problem of high print and travel speeds: acceleration.

The stock acceleration of this printer is 800mm/sec². The default acceleration for Marlin is 3000mm/sec².

With the top speed of the print and travel moves set to 300mm/sec, and the acceleration set to 800mm/sec², the printer might never even reach those speeds. At these travel settings, the print head will only reach a speed of 300mm/sec after about 50mm. Fast travel and print speeds are great if you’re building a printer with a meter long build plate (more on that later), but if you plug a few numbers into [Prusa]’s handy acceleration calculator, you’ll find you need acceleration to hit those travel speeds, anyway.

I don’t know why this machine shipped with a default acceleration of 800mm/sec². The default acceleration for the Marlin Firmware is 3000mm/sec², and every RepRap I’ve seen seems to do alright with that. The default acceleration can be changed through the on-screen menu, though, and after changing it, the printer performed very well.

Fast travel and low acceleration mean the specs are overly ambitious at best, and slightly deceptive at worst. Of course ambition or deception doesn’t matter, as all of this can be fixed with a few changes in the settings. I’d recommend setting the acceleration at 2000-3000mm/sec² (configurable through the OLED menu), and setting the slicer to around 100mm/sec. That’s a good ballpark for this printer.

The Guts

Twenty four Volts. Finally. Since the early days of RepRap, printers have been built with twelve volts in mind. Hotends were designed for 12V. Heated build plates were designed for 12V. Slowly, this has been changing, and I would suggest to anyone who wants to build their own printer to choose 24V. V=IR, and higher voltage means the hotend comes up to temperature quicker. You can push filament through a nozzle faster. Commercial printers have been slow to catch on. Not this printer, it’s 24V. The heated bed comes up to temperature quickly, and is almost impressive in that it’s heating a quarter-inch aluminum plate.

Unscrew four screws on the bottom of the machine, and the guts are revealed. Underneath the printer you’ll find the power supply, the controller board, and the OLED/knob/SD card board.

The controller board is based on the ATmega2560, but is not based on any board I can readily identify. It does use integrated stepper drivers, and there do seem to be a few spare connections available should I ever want to dig into this board to add an enclosure heater. No, it’s not an ARM board with fancy acceleration, but that’s the future and this is a 3D printer from the present.

The OLED display/interface is, as far as I can tell, exactly the same as a Ultimaker. There are options to set the motor current, and the bed leveling wizard is exactly the same. For anyone who has ever used a Ultimaker, the interface for this printer will be very familiar.

Contextualizing I’ll take my 3D printing cred now, thanks.

Deep in my email inbox, dated almost exactly five years ago today, I hold an invoice for Lulzbot order #000032. Take this as proof I have seen this industry grow before my eyes, and I’m a big believer in what Open Hardware can do.

Today, Lulzbot is going gangbusters, the TAZ 6 is still completely open source, and Lulzbot is the perfect example of what you can do with Open Hardware. The RepRap project and Lulzbot in particular have upended an entire industry, forced innovation, greatly expanded the mind share of a technology. 3D printers can print Pokemon. It doesn’t get more revolutionary than that.

The $200 MP Select Mini is the antithesis of Open Hardware. It is not built for modification. You can’t get spare parts. It is a black box, and when it breaks, you’ll just buy another. You don’t own that printer, it owns you. I can accept the low-end Monoprice printer, though. It’s just enough to get someone interested in 3D printing, it can print parts for a better 3D printer.

I don’t know if you can print a better 3D printer with the Monoprice Maker Ultimate. This $700 machine is capable of nearly everything you could ever want from a 3D printer. The quality of the prints coming out of this printer are really, really good. The potential for a (passively) heated enclosure is simply awesome. No, you’re not going to do dual extrusion, and the PTFE tube in the extruder won’t let you print really exotic plastics, but most people aren’t printing with those, anyway.

Compared to any printer you can build yourself, the Monoprice Maker Ultimate wins. It’s everything you need, and with a bit of tuning, know-how, and maybe an adapter to fix the fan issue, there’s nothing you can’t do with this printer. My poor Prusa Mendel weeps. The Open Hardware community should be philosophically opposed to this printer. It’s a true consumer 3D printer. Plug it in, turn it on, and in an hour or so you have some plastic trinkets in your hand. Learn how 3D printing works, and you can produce some really fantastic prints with this printer.

It’s a good printer, and I don’t think you’ll be disappointed.

In Conclusion…

Should you buy this printer? If you’re one of those people who would use GIMP instead of pirating Photoshop, no, this is not the printer for you.

For normal people, at $700, this printer is hard to beat. Software-wise, the stock firmware could use a bit of help, but everything that’s wrong with it can be fixed via the OLED control panel. Whoever is writing up the Monoprice manual and product copy needs to spend a few weeks cruising the RepRap forums.

This is a very good printer, and it’s very likely you won’t outgrow it. If you’re looking for your first 3D printer, you could do much worse and spend much more money in the process. It’s a bit higher quality than the innumerable $500 i3 clones I’ve seen (and at that price you should give Prusa a ring, anyway).  The Monoprice Maker Ultimate is a solid printer. Even though Monoprice won’t sell as many of these compared to their $200 MP Select Mini, they’ve done their job. The Monoprice Maker Ultimate is one of the best values in 3D printing I’ve seen, and should be on the short list for anyone planning to buy a printer for under $1000.

Concerning the question over the $700 Monoprice Maker Ultimate and the $800 Wanhao Duplicator 6, that’s an issue that could go either way. Judging from the availability of the MP Select Mini on Monoprice, I expect their Maker Ultimate to be out of stock often. For people whose patience is worth less than $100, this will tip the balance to Wanhao. That $100 impatience fee also gets you acrylic side panels and top. That isn’t a terrible deal, although I do desperately wish the US distributor would put a ‘Duplicator 6’ category in their online store.

Our Review Policy

It’s this. For this review, Monoprice provided me with this printer. Negative disclosure, or stating how this review was not influenced by a vendor or company, is an illegitimate concept and incompatible with civilized discourse.


Filed under: 3d Printer hacks, Featured, reviews

Impressive Junkyard CNC Made From Fancy Garbage

อังคาร, 08/30/2016 - 18:01

We’ll just come out and say it, [reboots] has friends with nice garbage. Sure, some of us have friends who are desperately trying to, “gift,” us a CRT monitor, hope dropping like a rock into their stomach when they realize they can’t escape the recycling fee.  [reboots] has friends who buy other people’s poorly thought out CNC projects and then gift him with the parts.

After dismantling the contraption he found himself with nice US and Japanese made linear motion components. However, he needed a CNC controller to drive it all. So he helped another friend clean out their garage and came away with a FlashCut CNC controller.

Now that he had a controller and the motion components whirring nicely, he really needed a frame to put it all in. We like to imagine that he was at a friend’s  barbeque having a beer. In one corner of the yard was an entire Boeing 747.  A mouldering scanning electron microscope with a tattered and faded blue tarp barely covering its delicate instrumentation sat in another corner. Countless tech treasures were scattered about in various states. It was then that he spotted a rusting gamma ray spectrometer in the corner that just happened to have the perfect, rigid, gantry frame for his CNC machine.

Of course, his friend obliged and gladly gave up the spectrometer. Now it was time to put all together. The gantry was set on a scavenged institutional door. The linear motion frames were bolted in place. Quite a few components had to be made, naturally, of scrap materials.

Most people will start by using a handheld router for the spindle. The benefits are obvious: they’re inexpensive, easy to procure, and generally come with mounts. But, there are some definite downsides, one of the most glaring of which is the lack of true speed control.

Even routers that allow you to adjust the speed (a fairly common feature on new models) generally don’t actually regulate that speed. So, you end up with a handful of speed settings which aren’t even predictable under load. Furthermore, they usually rely on high RPMs to do their work. For those reasons, handheld woodworking routers aren’t the best choice for a mill that you intend to cut metal with.

[reboots] noticed this problem while building this machine and came up with an inexpensive way to build a speed-controlled spindle. His design uses a brushless DC motor, controlled through a hobby ESC (electronic speed control), which uses a belt to drive the spindle. The spindle itself is mounted using skateboard bearings, and ends in an E11 collet (suitable for light machining in aluminum).

With the ESC providing control of the brushless motor, he’s able to directly control the spindle speed via software. This means that spindle speeds can be changed with G-code, allowing for optimized feeds and speeds for different operations. The belt-drive increases torque while separating the motor from the spindle, which should keep things cool, and reduce rotating mass on the spindle itself. Now all [reboots] needs to do is add a DIY tool changer!


Filed under: cnc hacks

Fixing the Ampere: Redefining the SI Unit

อังคาร, 08/30/2016 - 15:01

We all know that it’s not the volts that kill you, it’s the amps. But exactly how many electrons per second are there in an amp? It turns out that nobody really knows. But according to a press release from the US National Institute of Standards and Technology (NIST), that’s all going to change in 2018.

The amp is a “metrological embarrassment” because it’s not defined in terms of any physical constants. Worse, it’s not even potentially measurable, being the “constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per meter of length.” You can’t just order a spool of infinite length and negligible cross-section wire and have it express shipped.

So to quantify the exact number of electrons per second in an amp, the folks at NIST need an electron counter. This device turns out to be a super-cooled, quantum mechanical gate that closes itself once an electron has passed through. Repeatedly re-opening one of these at gigahertz still provides around a picoamp. Current (tee-hee) research is focused on making practical devices that push a bit more juice. Even then, it’s likely that they’ll need to gang 100 of these gates to get even a single microamp. But when they do, they’ll know how many electrons per second have passed through to a few tens of parts per billion. Not too shabby.

We had no idea that the amp was indirectly defined, but now that we do, we’re looking forward to a better standard. Thanks, NIST!

Thanks [CBGB123B] for the tip!


Filed under: news, slider

Hackaday Prize Entry: 1337 Haxxor Keyboards

อังคาร, 08/30/2016 - 12:00

If you’re like us, you spend most of your time in front of a computer keyboard, wondering where your life went wrong. [AnonymouSmst] has a slightly more positive outlook on life, which led them to create a truly DIY keyboard with OLEDs, Bluetooth, NFC, Analog joysticks, an ‘Internet of Things thingy’, local storage, and ostentatious backlighting. It’s a 1337 h4x0r keyboard, and one of the coolest input devices we’ve seen since that weird GameCube controller.

[AnonymouSmst] was one of the very elite, very privileged hackers that made it out to the Hackaday Munich meetup where [sprite_tm] first demoed his firmware hack that allowed anyone to play Snake on a keyboard. Here, the idea of building the ultimate keyboard was planted, and [mst] quickly began researching which keyswitches to use. Apparently, [mst] hates his neighbors and chose the obnoxiously loud Cherry Blues.

To a standard 60% keyboard layout, [AnonymouSmst] added a lot of hardware you don’t usually see in even the most spectacular mechanical keyboard builds. A few dozen WS2812 RGB LEDs were added to the build, as was an Adafruit Bluefruit module, an NFC reader, a LORA module and a ESP8266 for WiFi capability, an OLED display just because, and two analog joysticks on either side, one acting as the arrow cluster the other acting as a mouse.

We’ve seen dozens of mechanical keyboard builds over the years, but this takes the entire concept of a DIY keyboard to the next level. It’s bright, shiney, glowey, and a vulgar display of conspicuous consumption and engineering prowess. It is the perfect keyboard, if only because it was designed and built by the person who would ultimately wield it.

The HackadayPrize2016 is Sponsored by:
Filed under: The Hackaday Prize

Really Easy Jacob’s Ladder

อังคาร, 08/30/2016 - 09:00

There was a time when making a high voltage project like a Jacob’s ladder took time to build or scrounge some kind of high voltage circuit. The neon sign transformer, Marx generator, or voltage multiplier was the hard part of the project. But nowadays you can get cheap high voltage modules that are quite inexpensive. [PaulGetson] picked up one for under $20 and turned it into a quick and easy Jacob’s ladder.

Honestly, once you have high voltage, making a Jacob’s ladder is pretty simple. [Paul] used a cheap plastic box, some coat hanger wire, and some stainless steel bolts.

If you haven’t seen a ladder before, the theory is pretty simple. The high voltage ionizes the air between the two electrodes. The ionized air gets hot and since hot air rises, the spark rises with it, and the electrodes can get further and further apart. Once the spark rises above the electrodes, the process starts over again. You can see these in many old movies to signify some sort of mysterious scientific equipment.

We have covered Jacob’s ladders before, but few of them as simple as this. We’ve even seen simulated ladders, in case you are too timid to work with the high voltage.


Filed under: classic hacks

DIY Electric Pennyboard Can Hit 40Km/h!!

อังคาร, 08/30/2016 - 06:00

Home-made transportation is a thriving area for makers to flex their skills. Looking to shorten their university commute, [doublecloverleaf] modded his penny board by adding a motor that can have him zipping along at 40 Km/h!

The electric motor is mounted to the rear truck and delivers power to the wheel gear using a HTD 5 m pulley belt. Finding the deck too flexible to mount the battery pack under, [doublecloverleaf] strengthened it with a pair of carbon-fiber tubes bracketed on the underside. A few custom PCB boards connect ten 5 Ah LiPo battery cells in series to create two, five-cell packs which are kept safe by a thick housing mounted between the board’s trucks. [doublecloverleaf] calculates that they could make up to a 15 km trip on a single charge.

Thinking ahead, [doublecloverleaf] opted to use a DB25 port for charging — 9 pins for voltage balancing between cells within each battery, and ten more (five positive, five negative, in parallel) for charging at 5 A. A USB port allows him to tweak the VESC motor controller — this adds, among other useful features, regenerative braking!

A slightly modified RC car remote controls the motor — simply pull on the trigger to accelerate, and push to reverse and engage the regenerative breaking. It’s currently set to 80% of the motor’s max RPM at 40 A to preserve both the board and the rider’s health. Any faster, and they’d have to think about challenging the land speed record for electric skateboards.


Filed under: transportation hacks

Musical Proximity Detection Pet Bowls

อังคาร, 08/30/2016 - 03:00

An essential skill for a maker is the ability to improvise or re-purpose existing materials into new parts. Sometimes, one needn’t make many modifications to create something new, as is the case with [Robin Sterling] and his musical pet bowl.

Originally, it was a sealed pet bowl that opened when the proximity sensors detected an approaching pet. Having helped design the bowl, [Sterling] had a bit of an advantage when he decided to convert it into a theremin/light harp-esque instrument for the company BBQ. He routed the PWM outputs from each of the three proximity sensors (in each of the three bowls) to a small guitar amp, adjusting each sensor’s output to a different frequency. Despite the short amount of time [Sterling] had to practice, it works fairly well!

[Sterling] adds that the bowl’s firmware knows which proximity sensor is being triggered, making this an easy mod indeed. From musical bowls to refurbishing a paper-tape music box, or an entire musical ensemble with a constantly changing melody, the unity of maker and musician never ceases to amaze.


Filed under: misc hacks

Characterizing a Death Ray… er, Solar Oven

อังคาร, 08/30/2016 - 01:31

Many of you will probably at some point have looked at a satellite dish antenna and idly wondered whether it would collect useful amounts of heat if you silvered it and pointed it at the sun. Perhaps you imagine a handy source of  solar-cooked hotdogs, or maybe you’re a bit of a pyromaniac.

[Charlie Soeder] didn’t just think about it, he did it. Finding a discarded offset-focus DirecTV dish, he glued a grid of 230 inch-square mirror tiles to it and set to investigating  the concentrated solar energy at its focus. 

Cotton waste, newspaper, and scraps of fabric char and burn with ease. A cigarette is lit almost from end to end, and it burns a hole right through a piece of bamboo. Most of the energy is in the form of light, so transparent or reflective items need a little help to absorb it from something dark. He demonstrated this by caramelizing some sugar through adding a few bits of charcoal to it, once the charcoal becomes hot enough to caramelize the sugar around it the spreading dark colour causes the rest of the sugar to caramelize without further help.

Solar furnace calculations

To gain some idea of the power of his solar furnace, he recorded a time series of temperature readings as it heated up some water darkened with a bit of charcoal to absorb heat. The resulting graph had a flat spot as a cloud had passed over the sun, but from it he was able to calculate instantaneous power figures from just below 30W to just below 50W depending on the sun.

He records his progress in the video you’ll find below the break. Will we be the only ones casting around for a surplus dish after watching it?

We don’t seem to have had many satellite dish solar furnaces here on these pages, but we have had a more conventional solar oven or two. This dish-based solution would probably benefit from a sun tracker.


Filed under: green hacks, solar hacks

How Accurate Is Microstepping Really?

อังคาร, 08/30/2016 - 00:01

Stepper motors divide a full rotation into hundreds of discrete steps, which makes them ideal to precisely control movements, be it in cars, robots, 3D printers or CNC machines. Most stepper motors you’ll encounter in DIY projects, 3D printers, and small CNC machines are bi-polar, 2-phase hybrid stepper motors, either with 200 or — in the high-res variant — with 400 steps per revolution. This results in a step angle of 1.8 °, respectively 0.9 °.

Can you increase the resolution of this stepper motor?

In a way, steps are the pixels of motion, and oftentimes, the given, physical resolution isn’t enough. Hard-switching a stepper motor’s coils in full-step mode (wave-drive) causes the motor to jump from one step position to the next, resulting in overshoot, torque ripple, and vibrations. Also, we want to increase the resolution of a stepper motor for more accurate positioning. Modern stepper motor drivers feature microstepping, a driving technique that squeezes arbitrary numbers of microsteps into every single full-step of a stepper motor, which noticeably reduces vibrations and (supposedly) increases the stepper motor’s resolution and accuracy.

On the one hand, microsteps are really steps that a stepper motor can physically execute, even under load. On the other hand, they usually don’t add to the stepper motor’s positioning accuracy. Microstepping is bound to cause confusion. This article is dedicated to clearing that up a bit and — since it’s a very driver dependent matter — I’ll also compare the microstepping capabilities of the commonly used A4988, DRV8825 and TB6560AHQ motor drivers.

Microstepping Bipolar stepper motor symbol

In a hybrid stepper motor, a microstepping-enabled motor driver will adjust the current in the stator coils to position the permanent magnet rotor in an intermediate position between two subsequent full-steps. A full-step is then divided into a number of microsteps, and each microstep is achieved by the two coil currents.

Many older industrial motor drivers feature only 4 microsteps (quarter-step mode), but today, 16, 32 and even 256 microsteps per full-step are commonly found. If we had a 200 steps per revolution stepper motor before, we now have a 51,200 steps per revolution miracle. In theory.

Symbolic example of quarter-stepping in a bipolar stepper motor. The gradual current and field changes in each microstep cause the rotor to set in intermediate positions. Disturbingly simplified.

In practice, we’re still dealing with open-loop drivers, meaning that the motor driver does not know the exact angular position of the motor shaft, and it won’t correct deviations. Friction, the motor’s own detent torque and most strikingly, the external load that acts upon the rotor will go unnoticed by the driver. Without closing the loop through an encoder and a more sophisticated special driver, the best we can assume is that the motor will be somewhere ± 2 full-steps (yes, that bad) near its target position, which is the maximum deflection before the rotor snaps into the wrong full-step position, resulting in step-loss.

The incremental torque from one micro step to another is — governed by merciless trigonometry — only a fraction of the dynamic torque of the motor. To ensure that the motor shaft actually sets within +/- 1 microstep, we need to also reduce the load accordingly. Exceeding this smaller, incremental torque won’t result in step loss, but it will cause the same absolute positioning error of up to ± 2 full-steps. The table below shows the devastating relationship.

Microsteps per full-step Incremental holding torque per microstep 1 100 % 2 70.71 % 4 38.27 % 8 19.51 % 16 9.80 % 32 4.91 % 64 2.45 % 128 1.23 % 256 0.61 %

Source: Stepper Motor Technical Note: Microstepping Myths and Realities by Micromo

The good news is, that as long as we use a strong enough motor driver, and if we don’t exceed that incremental torque, be it through an external load or the motor’s internal inertia, the only theoretical limit for achieving microstep positioning accuracy are the motor’s internal friction and detent torque. These values depend heavily on the motor type, but are generally rather low (almost negligible) values. For example, the motor used in the following test is specified with a detent torque of 200 g cm. That’s merely 5% of it’s 4000 g cm holding torque. According to the above table, this motor should be capable of accurate positioning with a 16 microsteps per full-step driver.

So, does this theory apply? And do all microstep motor drivers deliver the same performance in terms of microstep positioning accuracy? I recently had the chance to test a few motor drivers for a project, and  I was rather surprised by the results.

Test Setup

For the test setup, I borrowed the red laser pointer from my IR thermometer and attached it to the motor through a 3D printed fixture. A 3D printed mirror mount attaches a first surface mirror to the motor’s shaft and features two levers with a length of 100 mm each for loading the motor with a given mass. For the load test, I attached a mass of 100 g to one lever, which results in a load momentum of 1000 g cm through the lever. That’s a quarter of the holding torque of the motor used for this test: A Wantai 42BYGHW609 with 1.7 A per phase, 4000 g cm holding torque and 200 steps per revolution.

I mounted the motor assembly to a rigid windowsill and positioned it so the laser pointer dot is projected across the room onto a pocket rule attached to the opposite wall, about 6 meters away. The optical lever magnifies the steps for accurate readings. Initially, I planned to just note down the readings manually, but then quickly realized that writing a little Java image processing script to extract the readings from photographs could be done in a fraction of the time. So a DSLR camera was hooked up to my test electronics — an Arduino and a RAMPS 1.4 — to be triggered for acquiring the position readings. I certainly should’ve pointed the laser at the clean, white wall next to the ruler, but a simple threshold on the red-channel did a good job in accurately extracting the bright red laser spot from the ruler. From the reading on the ruler and the distance on the wall, I later calculated the angular position of the motor shaft.

All stepper motor drivers were tested in their 16 microstep per full-step mode. Before the measurement, the stepper motor was brought into a full-step detent position, and the mirror was aligned to a beam perpendicular to the wall. Then 16 microsteps were executed in one direction while triggering the camera after every step. After that, 16 microsteps were executed in the reverse direction, bringing the stepper motor back to its original position. Again, the camera was triggered after each step. Measuring the position in both directions should allow me to get an idea of the motor’s cushioned backlash (if present), but resulted in more interesting insights than expected. This test sequence was executed for every driver, both unloaded and loaded with 1000 g cm. The stronger drivers caused a bit of overshoot during the loaded tests, so they were given time to come to rest before a photograph was triggered.

It’s worth mentioning that all following results originate from the very same motor, and the same physical motor step to ensure comparability. Nothing has been averaged or otherwise processed, except from calculating the shaft position angle. However, all tests have been performed multiple times on different hardware (i.e. the same driver IC, but different breakout boards from different sources) to ensure sanity of the results. Even the quirky results (such as the DRV8825) were reproducible on different setups. Please be aware that the following graphs may give the false impression of a time-continous measurement. They actually show a series of discrete measurements at the marks on the x-axis, and the line graph only should make it easier to see the non-linearities at a glance.

Allegro A4988

The Allegro A4988 on a Pololu stepper driver breakout board performed the best, both unloaded and under load. Even though it only delivers 1 A per phase, it achieved very linear, equally spaced microsteps in the unloaded test, with small but reproducible deviations from the ideal position within ± 1 microstep. Interestingly, the A4988 shows its largest deviation at the half-step position.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

Unsurprisingly, the shaft position is deflected noticeably under load: more than a half full-step. There goes the dream of infinite resolution. However, the graph also shows that the full-step positions aren’t immune to this deflection, even though they are supported by the motor’s slight detent torque.

Texas Instruments DRV8825

The Texas Instruments DRV8825 on a Pololu stepper driver breakout board performed the worst. I repeated the measurement several times with different breakout boards from different sources, all of them resulted in curves almost identical to this one. However, since the driver is capable of supplying a higher current of 2.2 A to the motor, it shows a significantly smaller deflection under load at the full-step and half-step positions.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

Both loaded and unloaded, the DRV8825 performs well until it reaches the half-step. Then, it leaps almost to the next full-step position within a single microstep. In the reverse direction, it again performs well until it reaches the half-step – this time in the other half of the full-step – before it breaks down to the original full-step position. The behavior is hard to explain. At least deficiencies in the motor’s current sensing path should affect the positioning more uniformly. I’m sure Hackaday readers can contribute to explaining, confirming, or disproving this behavior of the DRV8825, or maybe point out flaws in the measuring setup that could’ve caused these results.

Toshiba TB6560AHQ

I may admit I did not expect much from the cheap, red ST6560T4 driver board with four Toshiba TB6560AHQ 3A motor driver channels, but it’s a great driver IC and it did perform surprisingly well. The drivers were set to 2.25 A for this test and achieved a good linearity throughout the microstep sequence with a deviation of ± 2 microsteps when unloaded.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

There were, however, reproducible non-linearities at the upper full-step position which the A4988 did not show, and the TB6560AHQ’s behavior under load differs noticeably from the idle behavior. Also, it’s surprising that the motor is deflected under the load by more than a half full-step, since the higher current should increase the motor torque similarly to the DRV8825.

Conclusion

I hope this write-up and measurement results help you with your design decisions and when working with these very common drivers. I did this tests for a rather narrow application, and they shouldn’t be generalized too much. Although I dare to conclude the following:

Stepper motors in heavier machines, such as CNC routers, that use open-loop microstepping, mostly benefit from the reduced vibrations and the lower torque ripple of microstep mode. They can not rely on microstepping as a means of increased positioning accuracy (at least not without keeping large torque margins), since a load may still deflect the axis’s position by more than a full-step.

However, small and light applications with low load and low friction may indeed resort to microstepping as a cheap trick to squeeze more accuracy out of a standard stepper motor. Even with a cheap, low-current motor driver, looking at the very well performing A4988, accurate angular positioning is possible, as long as the load is kept low, ideally within the incremental torque of a microstep.

As always, I’ll be glad to hear your thoughts, opinions, and experiences on the subject of this post. What’s going on with my DRV8825s? What stepper motor drivers do you rely on most of the time? Let us know in the comments!


Filed under: cnc hacks, Engineering, Featured

How Accurate Is Microstepping Really?

อังคาร, 08/30/2016 - 00:01

Stepper motors divide a full rotation into hundreds of discrete steps, which makes them ideal to precisely control movements, be it in cars, robots, 3D printers or CNC machines. Most stepper motors you’ll encounter in DIY projects, 3D printers, and small CNC machines are bi-polar, 2-phase hybrid stepper motors, either with 200 or — in the high-res variant — with 400 steps per revolution. This results in a step angle of 1.8 °, respectively 0.9 °.

Can you increase the resolution of this stepper motor?

In a way, steps are the pixels of motion, and oftentimes, the given, physical resolution isn’t enough. Hard-switching a stepper motor’s coils in full-step mode (wave-drive) causes the motor to jump from one step position to the next, resulting in overshoot, torque ripple, and vibrations. Also, we want to increase the resolution of a stepper motor for more accurate positioning. Modern stepper motor drivers feature microstepping, a driving technique that squeezes arbitrary numbers of microsteps into every single full-step of a stepper motor, which noticeably reduces vibrations and (supposedly) increases the stepper motor’s resolution and accuracy.

On the one hand, microsteps are really steps that a stepper motor can physically execute, even under load. On the other hand, they usually don’t add to the stepper motor’s positioning accuracy. Microstepping is bound to cause confusion. This article is dedicated to clearing that up a bit and — since it’s a very driver dependent matter — I’ll also compare the microstepping capabilities of the commonly used A4988, DRV8825 and TB6560AHQ motor drivers.

Microstepping Bipolar stepper motor symbol

In a hybrid stepper motor, a microstepping-enabled motor driver will adjust the current in the stator coils to position the permanent magnet rotor in an intermediate position between two subsequent full-steps. A full-step is then divided into a number of microsteps, and each microstep is achieved by the two coil currents.

Many older industrial motor drivers feature only 4 microsteps (quarter-step mode), but today, 16, 32 and even 256 microsteps per full-step are commonly found. If we had a 200 steps per revolution stepper motor before, we now have a 51,200 steps per revolution miracle. In theory.

Symbolic example of quarter-stepping in a bipolar stepper motor. The gradual current and field changes in each microstep cause the rotor to set in intermediate positions. Disturbingly simplified.

In practice, we’re still dealing with open-loop drivers, meaning that the motor driver does not know the exact angular position of the motor shaft, and it won’t correct deviations. Friction, the motor’s own detent torque and most strikingly, the external load that acts upon the rotor will go unnoticed by the driver. Without closing the loop through an encoder and a more sophisticated special driver, the best we can assume is that the motor will be somewhere ± 2 full-steps (yes, that bad) near its target position, which is the maximum deflection before the rotor snaps into the wrong full-step position, resulting in step-loss.

The incremental torque from one micro step to another is — governed by merciless trigonometry — only a fraction of the dynamic torque of the motor. To ensure that the motor shaft actually sets within +/- 1 microstep, we need to also reduce the load accordingly. Exceeding this smaller, incremental torque won’t result in step loss, but it will cause the same absolute positioning error of up to ± 2 full-steps. The table below shows the devastating relationship.

Microsteps per full-step Incremental holding torque per microstep 1 100 % 2 70.71 % 4 38.27 % 8 19.51 % 16 9.80 % 32 4.91 % 64 2.45 % 128 1.23 % 256 0.61 %

Source: Stepper Motor Technical Note: Microstepping Myths and Realities by Micromo

The good news is, that as long as we use a strong enough motor driver, and if we don’t exceed that incremental torque, be it through an external load or the motor’s internal inertia, the only theoretical limit for achieving microstep positioning accuracy are the motor’s internal friction and detent torque. These values depend heavily on the motor type, but are generally rather low (almost negligible) values. For example, the motor used in the following test is specified with a detent torque of 200 g cm. That’s merely 5% of it’s 4000 g cm holding torque. According to the above table, this motor should be capable of accurate positioning with a 16 microsteps per full-step driver.

So, does this theory apply? And do all microstep motor drivers deliver the same performance in terms of microstep positioning accuracy? I recently had the chance to test a few motor drivers for a project, and  I was rather surprised by the results.

Test Setup

For the test setup, I borrowed the red laser pointer from my IR thermometer and attached it to the motor through a 3D printed fixture. A 3D printed mirror mount attaches a first surface mirror to the motor’s shaft and features two levers with a length of 100 mm each for loading the motor with a given mass. For the load test, I attached a mass of 100 g to one lever, which results in a load momentum of 1000 g cm through the lever. That’s a quarter of the holding torque of the motor used for this test: A Wantai 42BYGHW609 with 1.7 A per phase, 4000 g cm holding torque and 200 steps per revolution.

I mounted the motor assembly to a rigid windowsill and positioned it so the laser pointer dot is projected across the room onto a pocket rule attached to the opposite wall, about 6 meters away. The optical lever magnifies the steps for accurate readings. Initially, I planned to just note down the readings manually, but then quickly realized that writing a little Java image processing script to extract the readings from photographs could be done in a fraction of the time. So a DSLR camera was hooked up to my test electronics — an Arduino and a RAMPS 1.4 — to be triggered for acquiring the position readings. I certainly should’ve pointed the laser at the clean, white wall next to the ruler, but a simple threshold on the red-channel did a good job in accurately extracting the bright red laser spot from the ruler. From the reading on the ruler and the distance on the wall, I later calculated the angular position of the motor shaft.

All stepper motor drivers were tested in their 16 microstep per full-step mode. Before the measurement, the stepper motor was brought into a full-step detent position, and the mirror was aligned to a beam perpendicular to the wall. Then 16 microsteps were executed in one direction while triggering the camera after every step. After that, 16 microsteps were executed in the reverse direction, bringing the stepper motor back to its original position. Again, the camera was triggered after each step. Measuring the position in both directions should allow me to get an idea of the motor’s cushioned backlash (if present), but resulted in more interesting insights than expected. This test sequence was executed for every driver, both unloaded and loaded with 1000 g cm. The stronger drivers caused a bit of overshoot during the loaded tests, so they were given time to come to rest before a photograph was triggered.

It’s worth mentioning that all following results originate from the very same motor, and the same physical motor step to ensure comparability. Nothing has been averaged or otherwise processed, except from calculating the shaft position angle. However, all tests have been performed multiple times on different hardware (i.e. the same driver IC, but different breakout boards from different sources) to ensure sanity of the results. Even the quirky results (such as the DRV8825) were reproducible on different setups. Please be aware that the following graphs may give the false impression of a time-continous measurement. They actually show a series of discrete measurements at the marks on the x-axis, and the line graph only should make it easier to see the non-linearities at a glance.

Allegro A4988

The Allegro A4988 on a Pololu stepper driver breakout board performed the best, both unloaded and under load. Even though it only delivers 1 A per phase, it achieved very linear, equally spaced microsteps in the unloaded test, with small but reproducible deviations from the ideal position within ± 1 microstep. Interestingly, the A4988 shows its largest deviation at the half-step position.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

Unsurprisingly, the shaft position is deflected noticeably under load: more than a half full-step. There goes the dream of infinite resolution. However, the graph also shows that the full-step positions aren’t immune to this deflection, even though they are supported by the motor’s slight detent torque.

Texas Instruments DRV8825

The Texas Instruments DRV8825 on a Pololu stepper driver breakout board performed the worst. I repeated the measurement several times with different breakout boards from different sources, all of them resulted in curves almost identical to this one. However, since the driver is capable of supplying a higher current of 2.2 A to the motor, it shows a significantly smaller deflection under load at the full-step and half-step positions.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

Both loaded and unloaded, the DRV8825 performs well until it reaches the half-step. Then, it leaps almost to the next full-step position within a single microstep. In the reverse direction, it again performs well until it reaches the half-step – this time in the other half of the full-step – before it breaks down to the original full-step position. The behavior is hard to explain. At least deficiencies in the motor’s current sensing path should affect the positioning more uniformly. I’m sure Hackaday readers can contribute to explaining, confirming, or disproving this behavior of the DRV8825, or maybe point out flaws in the measuring setup that could’ve caused these results.

Toshiba TB6560AHQ

I may admit I did not expect much from the cheap, red ST6560T4 driver board with four Toshiba TB6560AHQ 3A motor driver channels, but it’s a great driver IC and it did perform surprisingly well. The drivers were set to 2.25 A for this test and achieved a good linearity throughout the microstep sequence with a deviation of ± 2 microsteps when unloaded.

Step 1 to 16 are in positive direction, step 17 to 32 go in negative direction.

There were, however, reproducible non-linearities at the upper full-step position which the A4988 did not show, and the TB6560AHQ’s behavior under load differs noticeably from the idle behavior. Also, it’s surprising that the motor is deflected under the load by more than a half full-step, since the higher current should increase the motor torque similarly to the DRV8825.

Conclusion

I hope this write-up and measurement results help you with your design decisions and when working with these very common drivers. I did this tests for a rather narrow application, and they shouldn’t be generalized too much. Although I dare to conclude the following:

Stepper motors in heavier machines, such as CNC routers, that use open-loop microstepping, mostly benefit from the reduced vibrations and the lower torque ripple of microstep mode. They can not rely on microstepping as a means of increased positioning accuracy (at least not without keeping large torque margins), since a load may still deflect the axis’s position by more than a full-step.

However, small and light applications with low load and low friction may indeed resort to microstepping as a cheap trick to squeeze more accuracy out of a standard stepper motor. Even with a cheap, low-current motor driver, looking at the very well performing A4988, accurate angular positioning is possible, as long as the load is kept low, ideally within the incremental torque of a microstep.

As always, I’ll be glad to hear your thoughts, opinions, and experiences on the subject of this post. What’s going on with my DRV8825s? What stepper motor drivers do you rely on most of the time? Let us know in the comments!


Filed under: cnc hacks, Engineering, Featured

Hackaday Prize: 20 Projects That Are The Height Of Automation

จันทร์, 08/29/2016 - 23:01

Automation makes the world go around. Whether it’s replacing elevator attendants with buttons, replacing songwriters with computer algorithms, or giving rovers on Mars the same sense and avoid capability as a Tesla, Automation makes our lives easier and better. Today we’re excited to announce the twenty projects that best demonstrate the possibilities of Automation in the running for the 2016 Hackaday Prize. These projects tackled problems ranging from improving the common stepper motor to flying Lidar around a neighborhood on a gigantic ducted fan.

The winners of the Hackaday Prize automation challenge are, in no particular order:

If your project is on the list, congrats. You just won $1000 for your hardware project, and are now moving up to the Hackaday Prize finals where you’ll have a chance to win $150,000 and a residency at the Supplyframe DesignLab in Pasadena.

If your project didn’t make the cut, there’s still an oppurtunity for you to build the next great piece of hardware for The Hackaday Prize. The Assistive Technologies Challenge is currently under way challenging you to build a project that helps others move better, see better, or live better.

We’re looking for exoskeletons, a real-life Iron Man, a better wheelchair, a digital braille display, or the best educational software you can imagine.

Like the Design Your ConceptAnything GoesCitizen Science, and Automation rounds of the the Hackaday Prize, the top twenty projects will each win $1000 and move on to the Hackaday Prize finals for a chance to win $150,000 and a residency at the Supplyframe DesignLab in Pasadena

If you don’t have a project up on Hackaday.io, you can start one right now and submit it to the Hackaday Prize. If you’re already working on the next great idea in assistive technologies, add it to the Assistive Technologies challenge using the dropdown menu on the sidebar of your project page.

The Hackaday Prize is the greatest hardware competition on Earth. We want to see the next great Open Hardware project benefit everyone. We’re working toward that by recognizing people who build, make, and design the coolest and most useful devices around.

The HackadayPrize2016 is Sponsored by:
Filed under: Hackaday Columns, The Hackaday Prize

Hackaday Prize: 20 Projects That Are The Height Of Automation

จันทร์, 08/29/2016 - 23:01

Automation makes the world go around. Whether it’s replacing elevator attendants with buttons, replacing songwriters with computer algorithms, or giving rovers on Mars the same sense and avoid capability as a Tesla, Automation makes our lives easier and better. Today we’re excited to announce the twenty projects that best demonstrate the possibilities of Automation in the running for the 2016 Hackaday Prize. These projects tackled problems ranging from improving the common stepper motor to flying Lidar around a neighborhood on a gigantic ducted fan.

The winners of the Hackaday Prize automation challenge are, in no particular order:

If your project is on the list, congrats. You just won $1000 for your hardware project, and are now moving up to the Hackaday Prize finals where you’ll have a chance to win $150,000 and a residency at the Supplyframe DesignLab in Pasadena.

If your project didn’t make the cut, there’s still an oppurtunity for you to build the next great piece of hardware for The Hackaday Prize. The Assistive Technologies Challenge is currently under way challenging you to build a project that helps others move better, see better, or live better.

We’re looking for exoskeletons, a real-life Iron Man, a better wheelchair, a digital braille display, or the best educational software you can imagine.

Like the Design Your ConceptAnything GoesCitizen Science, and Automation rounds of the the Hackaday Prize, the top twenty projects will each win $1000 and move on to the Hackaday Prize finals for a chance to win $150,000 and a residency at the Supplyframe DesignLab in Pasadena

If you don’t have a project up on Hackaday.io, you can start one right now and submit it to the Hackaday Prize. If you’re already working on the next great idea in assistive technologies, add it to the Assistive Technologies challenge using the dropdown menu on the sidebar of your project page.

The Hackaday Prize is the greatest hardware competition on Earth. We want to see the next great Open Hardware project benefit everyone. We’re working toward that by recognizing people who build, make, and design the coolest and most useful devices around.

The HackadayPrize2016 is Sponsored by:
Filed under: Hackaday Columns, The Hackaday Prize