Pages Menu
TwitterRssFacebook
Categories Menu

Recent videos

More
  • Engineering a better drummer?
  • Nano-meter precision positioning
  • Universal Robots

Most recent articles

Extend your battery life by keeping your computer OFF

Greener computing, computers that use significantly less power, might be coming soon.  How?

They turn themselves off between every keystroke, mouseclick, or touch.

The Journal of Applied Physics has published a very interesting article this week.  The technology, Magneto-resistive Random Access Memory (MRAM), is over a decade old now.  It uses two plates which can each be assigned a magnetic field direction.  The data is read back by measuring the resistance across the plates, if the reading is low resistance then the fields are aligned.  High resistance means they are opposing.

The size of the cells in in MRAM (each cell can store a bit) and the high current necessary to program them are the limiting factors in this technology, but enter the Spin Transfer Torque methodology.  This concept uses the spin direction of electrons to modify the magnetic properties, drastically shrinking the cell size, which increases the memory density.  This technology still has some development, but it has the advantage of significantly lower power demands.

Conventional DRAM requires a relatively high percentage of a computer’s power demands, it uses a small capacitor to store an electric charge with a transistor to control it.  This means it is constantly drawing current from the main computer power source.  MRAM-STT needs power when modifying a bit, but otherwise can be shut down.  For any given bit in memory, it is likely that it spends more time being unchanged than changed, meaning the majority of time it can be shut down.  The concept of the article is that it would be possible to build a computer that shuts itself down whenever there is a break in usage of a few milliseconds, then turn itself instantly back on.  The power savings would be immense, and could allow computers to be run off alternative energy sources (solar, hand-crank, thermal).

There are quite a few details yet to be worked out.  If you were  to read through the journal article, you would see that there are still limitations in size and speed, but the analysis shows that we are still moving toward the end goal of a more energy efficient computer.  Personally, I’m looking forward to cell phones that can last through the day while actually using them continuously.

 

K. Ando, S. Fujita, J. Ito, S. Yuasa, Y. Suzuki, Y. Nakatani, T. Miyazaki, and H. Yoda. Spin-transfer torque magnetoresistive random-access memory technologies for normally off computingJournal of Applied Physics, 2014 DOI:10.1063/1.4869828

Midi Controller construction complete!

I actually finished the controllers a few weeks ago, but haven’t had time to do an update!

They ended up working well, although much more difficult to use than anticipated!  While playing guitar and singing already, adding the foot action is harder than it was with my old mechanical setup.

Midi foot controller

Final controller

Here’s what they ended up looking like:

I never explained the button layout, but basically the problem was how to fully represent a 12 note scale while keeping all the buttons within easy reach.  They also needed to be laid out so that there are no ‘accidental’ pushings.

I designed this 7 button layout as a replacement for the typical 12 note piano style that is used by many foot controllers.

Each button is a ‘white’ key, with C on the left and B on the right.  If you want a sharp or flat ‘black’ key, just hit the two buttons simultaneously on either side of where it would be.  Getting the double button press working correctly was the biggest challenge of the programming process.  I ended up using a modified debounce routine that ensured both buttons were firmly pressed prior to sending a note on command.

The other three switches are ‘octave up’, ‘portamento’, and ‘fifth chord’ parameter changes.

 

Bending the sheet metal

Bending the metal electronics enclosure using a cheap Harbor Freight sheet metal brake. The clamps are a must to ensure a good bend!

Drilling large holes.

Knockout punches are incredibly expensive, fortunately since the metal is aluminum I can avoid them. By clamping two pieces of trash wood onto the metal, I can simply use a hand drill with large wood bits to cut the holes for mounting the electrical connectors.

Drilling

Another shot of the drilling process.

Clean holes
Here you can see the result of my drilling method. Very clean holes!

Internal electrical wiring

I had to use some temporary hardware to hold everything together until I got the right screws and nuts. You can see how the USB to USB connector makes the connection very clean, rather than running wire through the metal enclosure.

You can see the connectors a bit better in this shot.  I highly recommend using the USB connector rather than dealing with wires running through metal holes or soldering USB cabling.  I'd rather have the USB pulled out of the connector than have someone rip the wire out internally!

You can see the connectors a bit better in this shot. I highly recommend using the USB connector rather than dealing with wires running through metal holes or soldering USB cabling. I’d rather have the USB pulled out of the connector than have someone rip the wire out internally!

Internals again.

Here is another look at the inside. Pretty much ready to seal it up.

So now I need to learn how to use all this stuff in a song, I’ll post a video when it happens!