AT&T U-Verse upstream speed bump in June

I have an AT&T U-Verse “Internet Pro” DSL account. In the middle of June (near the 13th) my latency suddenly improved by 10ms.

Then around the 19th of June (2014) my upstream bandwidth jumped from around 1 Mb/s to around 1.4 Mb/s:

AT&T doesn’t advertise or make any promises about their upstream bandwidth, but these are welcome changes (especially the 40% boost in upstream bandwidth). My downstream bandwidth stayed just above the advertised 3 Mb/s rate.

I don’t know if this was due to a piece of equipment near my home getting upgraded, or the result of a policy change to upgrade the “Internet Pro” account, but I’ll take it!
Anybody else see a similar boost? Or have a negative counter example?

Editing cellphone videos in Ubuntu Linux

If you have a slightly older android cell phone, chances are it records videos using the “3gp” format. When editing 3gp videos in OpenShot on Ubuntu, the audio and video can become unsynced. I have found that using the WinFF application you can convert the 3gp video into “DV – Raw DV for NTSC full screen” format, which will allow OpenShot to edit it correctly without having audio sync problems.

As a side note, sometimes when shooting videos with a cell phone, you may forget to rotate the phone to “landscape” orientation and be left with a vertical video that is rotated 90 degrees when shown on a computer. OpenShot can be used to rotate videos as follows:

  1. right click on the clip
  2. click Properties
  3. Choose the Effect tab (far right)
  4. Hit the “+” sign and then scroll down to “R” for Rotate.
  5. In the effects settings:
    • set the Rotate X, Y and Z to 0.00
    • set the Fixed Rotate X variable to 90.0.
  6. Hit apply

Playing a USB midi keyboard on Ubuntu Linux

I purchased a USB MIDI keyboard (the Alesis Q25) for use with my musical Tesla coil, but also wanted to use it to learn to play the keyboard/piano when traveling with my laptop.

The MIDI keyboard has no synthesizer of it’s own, so you need a computer that will take the MIDI data stream and play (synthesize) the actual sounds of a piano or other instrument so that you can “hear” what you are playing.

There are many pieces of complicated software on Linux that will allow you to compose music with a MIDI keyboard, but all I wanted was the ability to hit a key on my keyboard and have it make music.

The easiest set of software I found to do this was vmpk (virtual midi piano keyboard) combined with Qsynth (a GUI interface to fluidsynth). I started up qsynth and vmpk at the same time. Then I used the “edit->connections” menu on vmpk to set my MIDI keyboard as the incomming connection, and the “FLUID Synth (Qsynth1)” as the output connection.

To set up qsynth I hit the “setup” button and then in the MIDI tab selected the “alsa_seq” as the MIDI Driver and “qsynth” as the MIDI Client Name ID (ALSA/CoreMidi).
I also enabled the soundfront from the /user/share/sounds/sf2 folder.
I don’t know why I had to use vmpk to make this linkup between the keyboard and Qsynth, but so far I haven’t found an easy way to tell Qsynth to just listen to midi events from the keyboard directly. On the plus side, you can use the virtual keyboard that vmpk displays on the screen to play notes if you don’t actually have a physical USB MIDI keyboard.

oneTesla playing the Imperial March

Here is the coil with my custom top facing breakout point playing the Imperial March.

Here is a photo of the Tesla Coil:
Tesla coil sparking

OneTesla O-scope traces

I have reduced my primary to 5 turns, and using the standard 0.068 MFD tank cap, this is the general shape of my oneTesla output waveform (as captured by a scope probe hanging in the air about 3 feet away from the coil):
Screen Capture

As you can see, the primary rings up and then the secondary oscillates for quite a while afterwards.

The next three traces are running the coil at a very low power level. Depending upon where I measure between peaks on the trace, I get different frequencies:

Screen Capture
277 kHz

Screen Capture
294 kHz

Screen Capture

17.80 uS between five peaks, or 1 / (3.56 / 1000000) = 280 kHz

As the 280 is between the 277 and the 294, we’ll just say that my primary has a resonant frequency of 280 kHz, when at low power.

Next, I turned the power up a bit (around 1/3 of the way up) and got the following two measurements:

Screen Capture
263 kHz

Screen Capture
18.40 uS for 5 peaks, or 1 / (3.68 / 1000000) = 272 kHz

So my primary resonance is somewhere between 263 and 294 depending upon how I measure it, with a value of 272-280 looking to be a reasonable average.

Surprisingly, my secondary resonance measurements agreed with themselves a bit better. Here is the low power trace:
Screen Capture

And the “Mid Power” trace.
Screen Capture
(You can see the primary ringing extending out so that it becomes visible in the trace…)

In both cases, I measured 15.20 uS between 5 peaks or
1 / (3.04 / 1000000) = 329 kHz

So my ratio is currently 329 / 280 or 1.175 ( Secondary 17-18% higher than my primary).

oneTesla top breakout point for my musical Tesla coil

Since I’ll be primarily using my oneTesla to play music, I wanted a top facing breakout (so the sparks will shoot up, instead of out to the side). Also, I wanted something more professional looking than a stick of metal taped to the top of the toroid. Here is the final product on the top of my toroid:

You can visit [ this post ] to see a video of it in action.
I used the lathe to get the general shape I wanted:

Then turned it to even up the 15 degree angle:

And this is my original 1″ diameter aluminum stock. I tapped it for the 14-20 bolt on the top of my Tesla coil that normally has a wing nut to hold the stamped toroid together, so the whole thing just screws onto the top.

Turning custom extruder parts


This is my new extruder hot end. After enclosing my printer with an insulated box, I decided that I needed to drop more heat before the plastic entry side of the end of the barrel. I accomplished this by turning an extra long barrel out of brass, and a small heatsink out of aluminum to go between the heater and the Groove Mount.

You can see the barrel compared to the original part here:

The barrel was straightforward to turn out of a piece of 1/4″ hex stock. I put the threads on with a metric M6x1 die.

The HeatSink took more time, mostly because I had to cut the fins out of a 1″ diameter rod quite deeply with a cut-off tool.

I compressed the several hours of work on the heatsink down into a six minute video below:

Turning Punches

I’ve finished reading the Home Machinists Handbook by Doug Briney and am starting on some of the projects. Project 1: Make your own center and prick punches.

prick punch and center punch

All finished except for the heat treating to harden the steel. Each punch was about 0.19 USD worth of steel, plus an hour of (technical, but non-union) labor.

CaseModding my 3D printer’s insulated cover

After building an insulated cover for my 3D printer, I decided that I needed to put some lights inside. This allows me to see how the print job is progressing, both via the porthole, and via the interior webcam. Because green surplus neon tubes for computer cases are inexpensive and take 12 volts, I riced up the cover with two green neon tubes. The color complements the light teal of the foam insulation nicely, and gives my Garage Laboratory an evil green glow at night.

Insulated cover for my RepRap

My 3D printer lives in the garage. I use it to print ABS plastic, so the smell needs to be out there. However, as my garage is unheated, I have problems with ABS prints warping and cracking, especially during the winter due to the cold air around the part as it is printed. To solve this problem (and get better performance even in the summer) I built an insulated cover for my 3D printer.


I cut a round viewport in the door that is covered by shrink fit window insulation plastic. Continue reading →