Fighting with computers

Computers are not always friendly.

Sunday, February 28, 2016

A couple of ideas for right corners with 20x20 extrusions

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:

Other times the profile is so tight that no screw can fit in the inside channel, so then this other approach can be used:

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).

Sunday, February 14, 2016

Testing another brushless motor

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 shaft (a drop of superglue helped here). A small carrier board in the center of the plastic box keeps the sensor IC close to the shaft's magnet.

One of the unexpected benefits of using a brushless motor is that this one came with a built-in driver, so there is no need of additional electronics besides the loop controller. In this case I keep on using the ESP12E (or NodeMCU) that Mauro Manco kindly provided me a few weeks ago. But this time the part gave me some pain too. It turns out that PWM was not always giving the right output. it is is a software-based PWM and I was getting all the outputs for 8-bit PWM right except the value for 254 that turned out to be the same output as 0. That won't be a bit problem unless your motor's PWM input is inverted, like this motor I am using. Long story short, I had to lower PWM frequency to 10Khz to get it working ok. 

As usual you can get the source code from my dcservo github. And the 3D printed cover.

Monday, February 01, 2016

Windows 10: Upgrade if you can

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 performance AMD-based HP laptop with 3GB of RAM. The process started smoothly but after one day I could only see a rotating sign below the Windows icon on the screen while zero hard-disk activity was happening.  Tired of waiting after more than 24h I powered cycle the laptop: on booting up the system crashed and I thought I totally screw it up, but on the second reboot the upgrade was able to continue. But apparently only to keep on doing the same. I left it to its own devices for three more days with no apparent change. So I decided to power-cycle it again. At this point I was really lamenting to have attempted the upgrade and I was thinking I might need to reinstall the system. However, I was pleasantly surprised to see a message on the screen saying that Windows was reverting to the previous Windows version. And twenty minutes later the system was brought back to life from the death.  I, for one, have to congratulate Microsoft people decided to put forward this escape route.

I have not explored Windows 10 deep enough to have an informed opinion but so far I am glad the start menu is back.