Fighting with computers

Since I got a beta version of Hephestos 2 from BQ before its launch, I have been using that printer more and more. After the initial annoyance about doing things on a certain way (like heating the extruder before performing a home move on an axis) I have got used to these details and I do not care anymore. And with a few exceptions were a part bottom failed to stick to the bed (nothing that a bit of hairspray could not fix) the printer has been delivering consistently quality prints. Z-axis became a bit noisy on long moves but I have no other complaints. However,  all the time I have been using PLA or Filaflex on a cold bed. There is no provision for a heated bed add-on so I had a look around for a stand-alone temperature controller.  I have found a simple pcb unit with display that controls a relay for a heating load up to 20A. Not sure how long that relay could last but for less than $5 I am going to give it a try. Next the bed, I do like aluminium beds with powe...

I am working on an Art project that requires some radio-reception capability on a Raspberry Pi. I available online . But given the local nature of the data I need to treat this time I have to use a local receiver. have used in the past some interesting website that feature an SDR device whose reception is One suitable device I found very inexpensive are DVB-T USB dongles originally intended for watching Digital TV on a computer. These dongles can be had for less than $10 on eBay. The good thing is that the chipsets employed are Linux supported and there is a bunch of useful software that can use them as a Software Defined Radio (SDR). What is SDR? Well, basically it can act as a multipurpose radio scanner for many different purposes as spectrum usage recorder, amateur radio receiver or just listening to FM radio or airplane ADS-B transponders. For that latter purpose there is a cool program called dump1090 that will receive and decode the messages of the airplanes' tra...

After watching a video of a new pen plotter made by Evil Mad Scientist we wanted to have a similar device. And having a 3D printer at hand plus some CAD software like Onshape or Fusion 360 it was a good exercise to design the whole thing. As usual the process was not completely straightforward, as initially it was more about copying the model we saw but as things were coming together some new ideas were explored. So while the first mock-up was based entirely on laser-cut parts (some of them glued together to make them thicker as the crappy laser I have access to is really depth limited as it is low-power).  Why laser-cut? Well because it was faster (or so it was supposed, but don't get me started on that). Once the first model was put together several ideas pop up: First, motors are in the way of carriage motion and reduce a bit carriage travel along smooth rods. Second, motors require another part that could be fused with the machine feet and rods support. Third, t...

While the Wire library allows you to get I2C working right off the bat with Arduino, there are times when the built-in Wire library does not do it. For some people this happens because they need to do a repeated start condition or to receive a large number of bytes, tasks that seemed to be not possible with Wire library. But for me the problem this time is a bit odd: I had to overcome the limitation of each I2C device to have a different address. It turns out that I am using a magnetic encoder chip that responds to a given address that cannot be changed. Because I want to be able to access at least two similar encoders from on Arduino board I find myself in the unlikely situation where I have to use two different I2C buses, one per device. However, I2C interface was designed to do the exact opposite thing, allowing several devices to communicate over the same bus (provided each one had a different address of course). As second detail I have been interested is to speed up the commun...

A recent update of Chrome brought me some trouble with various web content, including PDF viewing. Apparently some change in how layers are handled makes the viewing of PDF content almost impossible: you see some bars of the underlying PDF file but only as a flicker while you scroll down the document, as if some black layer was on top of it. A quick check online  revealed that many people using OSX versions before El Capitan were complaing about exactly that same thing.  And while Google seemed not to be offering a solution at the moment (and upgrading to El Capitan was not something I would like to do right now) some users suggested that disabling hardware acceleration in the browser would help. However, disabling hardware acceleration might solve this issue but create other problems with other content or just degrade browsing performance, so I did not want to go that way either. Finally, another user suggested the install of a browser extension (in fact replacing Chrom...

Some aluminium extrusions are quite convenient for building various types of structures. Manufacturers usually have a lot of choices when it comes to making unions. However, you not always have the time to wait for a part to be shipped to make a connection. Other times it can be done more cheaply and easily if you can use a drill. For certain 20x20 profiles, I have used an M6 screw to make right angle joints. The inside hole of the extrusion needs to be tapped and an additional hole will help for tightening the screw with an allen tool: Corner by misan on Sketchfab Other times the profile is so tight that no screw can fit in the inside channel, so then this other approach can be used: Corner2 by misan on Sketchfab My original CAD had the screws with a distinct color but that was lost in translation :-( If you clic on the images below you can have a look at the same model in Autodesk A360 Image viewer (unfortunately it only works for a month). ...

For my closed-loop control project I considered brushless motors to be a superior choice but the lack of affordable models in the marketplace let me down a bit. I was able to find some cheap models on eBay but those were lacking of built-in encoder and my attempt to add them one was a bit of a mess: the optical disk and sensor require better alignment that my poor skills could provide, so it ended up not being reliable. On the other hand, most DIY can get a small part 3D printed and my previous tests with magnetic encoders encourage me to use them more often. So I took some time to tinker with a motor from Nidec and how I could get an encoder attached in a simple way. The end result is what you can see in the picture below, that just consist of a 3D printed part with three fingers that attach to the back of the motor's plastic cover notches. You can see in the picture below the hole in the plastic box through which a small plastic part holds the magnet to the motor's sh...

Since 2000 I am on a Windows-free diet. But that does not mean that I am totally ignoring Windows, after all, it is what most people use. So I have a few computers still running XP, Windows 7 and Windows 8.1. Last week a couple of my laptops offer me the chance to upgrade to Windows 10. A few weeks a friend bought himself a nice Bang & Olufsen laptop equipped with Windows 10. My friend is a long-time Windows sufferer and he seemed to be quite happy with the latest Windows version. So I decided to bite and try the upgrade by myself. My first system was two years old Toshiba laptop with an i5 and 8 GB of RAM. I started the upgrade and everything went smoothly though terribly slow, the whole process taking perhaps ten hours (not sure exactly how long as I went to bed, bored of waiting. And I do not think download speed is to blame here as I have fast Internet connection at home (apparently a bit more than 2 GBytes are downloaded). My second system was an older, low performanc...

A few days ago I was talked on G+ by my friend Mauro Manco with an idea that was a bit weird at first: we all have heard about ESP8266 SoC that can bring Wifi happiness to out Arduino projects for a few dollars. What Mauro suggested is that this same unit might handle the servo code I have written for an Arduino. That was in part possible by the release of an SDK that allow us to program it the same way as a regular Arduino, so code-wise, programs are compatible. In a few attempts Mauro managed to get my code to compile happily for the ESP.  But he wanted me to try it out so he was as kind as sending me a NodeMCU board to my home so I could give it a try. It just arrived at noon and I could not resist to give it a try, as usual not without some minor problems. The first one was that the NodeMCU did not show up as a serial port in my Macbook. I tried installing the CH340 driver to no avail. After using a magnifying lenses I realised that the USB to serial adapter on my boa...

I was recently invited by Pablo Murillo to give a talk at Zaragoza Maker Show  and I wanted [among other things] to present a hands-on project to the audience, outlining the process I followed to get it done. I was lucky my friend and fellow "Arduinist" Colin Dooley gave me away a 15-led addressable RGB stripe a while ago. Unfortunately, the Cylon effect (aka Lasrson scanner for those old enough) was already taken as one example from FastLED library, so I had to do something else. I have chosen the title "Beyond Blink" for my talk , so it would be nice to get something that, while blinking, performed a more useful work. So what I decided was to use the 15-led stripe as some sort of presentations clock, that will help the speaker to know the time elapsed, a new led lit each minute, while of them is blinking each second. But as many talks are longer than 15 minutes, I repeated the same pattern with changing colours for each next quarter. Red being the last colo...

Since I published my DC motor control project on youmagine I have got some feedback from users with 2000 PPR (pulses per revolution) encoders or more where they end up having trouble above 3000 RPM. The reason is that the poor Arduino cannot process the interrupts fast enough and the system becomes unreliably. While optical encoders are available quite cheaply, some of the magnetic sensors from AMS are very competitive and offer very good accuracy (from 12 to 16 bits). One interesting model (due to its low price) is the AS5600, that provides a 12bit angle measurement for less than $2. Measurement data is read by means of an I2C serial bus and needs no interrupts. Hopefully those having trouble with interrupts can switch to this type of sensor, but model AS5600 is most likely a bad choice as it is intended to replace manual knobs in hi-fi equipment and it will not work at high RPMs (in fact the manufacturer does not provide the max RPM at all). But for position control applicati...

For my CAM project I was using a 3D offset of the parts to compensate for the tool diameter. But i have recently have incorporated a new feature so 3D assemblies of blocks can be represented in 3D. For the automatic assembly (courtesy of Carlos Sánchez) I cannot use the offset surfaces but I have to use the original meshes. One way of machining a 3D mesh is dropcutter algorithm, that in a nutshell works by modeling the milling bit and setting the z-depth at each XY location so the model is barely touched by the tool. As meshes are made of triangles, each feature of them is tested for contact: edges, facets and vertices. The feature with the highest z-depth value will set it for that particular location. I have found a lot of insight and useful information in Anders Wallin blog . Though my initial approach was to adapt his monocam's C# code to Java, I ended up with a buggy result. Anders released later a C++ library, opencamlib, that is most likely a much improved version, ...

I have just noticed there is a new version of Autodesk's Meshmixer software available for Linux but this time is no longer running over wine but it is compiled to run in Ubuntu 14.04 64bit. And the first tests suggest it works reliably (only crashed once when searching on the online 123D library). It is a great program and it is free to use so I find myself using it from time to time. There are quite interesting but unexpected uses . It is been a while since I last checked, so do not bash me if this is not new news for you, I now it was released first around March 2015, but I am a bit slow :-)

I wanted to create a simple schematic for my students. I could use an electronic CAD system but I needed something simple and quick. I look it up on the Internet and I have found a few choices. The first one was from Digi-Key and it worked nicely for my job as shown below (you may want to click on the image to get it to readable size). It was documenting the circuit of a simple electrostimulator to be used with an Arduino for creating some pain. One of my students wanted to build an Arts installation will cause him physical pain and this one fits the bill. For the rest of the people, the usual disclaimer is in place: use it at your own risk.

One of the most unpleasant experiences with computers is having to solve a problem you already fixed when you realize the old solution is no longer working for reasons unknown. The problem this morning was quite silly, actually. One piece of code created a text file. I did not care much about the way newlines were represented but when  I sent the file to to a colleague that uses Windows he complain notepad was making a mess out of it. It was clear notepad was doing this because my file, created on a unix system, did not honor Windows end of line convention of CR plus LF characters (0x0d + 0x0a). I have solved that in the past just changing the System property called line.separator. You could do that with System.setProperty("line.separator","\r\n") but apparently not anymore. Of course, no error message or exception is raised, so you are left alone, in the dark, trying to figure out what is wrong and why what worked before does not work now. I could not make m...

When I was a teenager I was an avid reader of electronics magazines. What was available at home at first and later what I could afford. I remember that my favorite ones was Elektor magazine, that grew from a German-only magazine to be distributed to other languages and countries, mine included. They have this great summer edition that included over a hundred different small circuits. Over the years I have almost stopped buying magazines (not because they are bad but because they use shelf space and I have not much time to read them). The last paper copies I bought were from Circuit Cellar Ink, but these same guys decided that a digital edition will ease their business, and for those abroad it will be be much cheaper. Selling bits is a good idea that seems to be making Google and many others much good. I even wrote several articles for Circuit Cellar magazine about different projects I made. A few years ago I learned that Circuit Cellar Ink was acquired by a European group that hand...

I was asked to be a beta-tester of this new machine sold in kit form by Spanish firm bq .  It's a bit hard to keep the experience to myself while the testing was taking place. I won't say it is great and rosy but their approach was a bold one and I think it stands out of the crowd. So what is it? Hephestos 2 is a 3D printer kit to be assembled by the user. While it might find its routes in Josef Prusa iteration 3 model, this time it is just a faded image. That was entirely the case with the former Hephestos that shared most of Prusa i3 features with a few of exceptions: no heated bed, a couple of cable chains and a very well engineered extruder/hotend combo. But the Hephestos 2 breaks with the Reprap tradition and includes no printed parts and a body made of powder colored folded metal parts. Only Y-axis uses 8mm diameter smooth rods and linear bearings but Z and X-axis use miniature Hiwin linear rails for extra accuracy. A new electronics board integrates an ATmega 2560 ...

The code I developed a while ago for using a DC motor (or a BLDC) to replace a stepper has got quite an interest among youmagine users. Over time I realized that some of the quick and dirty things I did were preventing the easy exploration of system parameters for users. Using different PID parameters required a recompile and of the sketch. I recently received a Printrbot Simple from Brook Drum with the goal of testing with that printer my closed-loop solution.  As usual, simple things (in theory) become tougher that initially expected. First of all, it took forever for the printer to clear through customs and while Printrbot provided and shipped the printer for free, the taxman wanted its cut no matter what, and it took more than too weeks for that to be worked out. We settled on the Simple because it had more room for the motors to fit in though carriages might be heavier than the Play. At the time I did not know the CAD of both models was available on Youmagine, so I...

One of my current projects requires to run two, maybe more in the near future, DIY CNC machines. Machine controller is USB-based and a PC could be used to send g-code to machine controller. However, we have tried a different approach that proved successful: using a cheap tablet instead of a PC. It all started by testing the excellent program GCodePrintr by Mathias Dietz. This software is designed so people can use a 3D printer directly from a tablet. You can stream a g-code file for printing to the printer plus you can do all the usual manual functions of moving the axis around. Besides, a graphical simulation of the print is represented on the display. And in the few tests I did, printing speed did not seemed to be compromised because the lower tablet performance (compared to a PC). However, uploading a file from Dropbox or using some FTP app for sending g-code files to the tablet was not very convenient as required user time spent at the tablet. But one feature of GCodePrintr ...

I needed for a project some metal holder plates for nema 23 motors. As I have in the lab a Chinese 6040Z CNC router I thought it will be an easy thing to do. Oh boy, how wrong I was. They project was a simple plate (very easy to sketch using OnShape ). Once it was sketched a 3D part could be created by simply extruding it, which may come in handy if some drawing assembly needs to be done for documentation purposes. However, for 2D projects a 3D model of the part is not really needed for the process of creating 2D machining code. There are different solutions out there that are free, but one that I like because it is very simple to use and it is on-line is makercam.com but for that you will need an SVG file instead of the DXF that OnShape can easily produce.  I usually use Inkscape software for converting to and from SVG and DXF. I did so in this case and it worked as expected. So, once I have got the SVG file I can feed Makercam.com I need not to forget to c...