Buy Electronic Parts in the USA

 Other Hardware  No Responses »
Aug 302011
 

If you need small electronic parts such as a AND gate in TTL logic, you may read on, how to find the parts you need and where to buy them.

To find out what part would fit your needs best, check out the manufacturers websites such as Texas Instruments:

To buy your stuff, go to any of the following websites (if you know another one that I didn’t state here, let me know by writing a comment):

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Lenses for SLR and DSLR cameras

 Other Hardware  No Responses »
Aug 292011
 

This is a table how the focal lengths of the old lenses for 35mm analogue SLR cameras translate to those of newer APS-C sized Canon image sensor based digital SLRs. I wrote this post to know about the equivalent focal lengths for my Canon Rebel T3 and my old lenses.

Make Lens Name Lens originally made for 35 mm APS-C with crop factor 1.6
Canon EF-S 18-55mm f/3.5-5.6 IS II APS-C 28.8 – 88 18 – 55
Canon EF 28-105mm f/3.5-4.5 USM 35mm 28 – 105 44.8 – 168
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Canon Rebel T3

 Other Hardware  1 Response »
Aug 282011
 

The Canon Rebel T3, in Europe called EOS 1100D is the entrance level digital SLR camera from Canon. The kit comes with the Canon EF-S 18-55mm f/3.5-5.6 IS II lens.

The kit includes

  • EOS Rebel T3 Body
  • EF-S 18-55mm f/3.5-5.6 IS Type II Lens
  • Eyecup Ef (not shown)
  • Wide Strap EW-200DB
  • Interface Cable IFC-130U
  • Battery Pack LP-E10
  • Battery Charger LC-E10
  • EOS Digital Solution Disk and Instruction Manuals “Great Photography is Easy” Booklet and “Do More with Macro” Booklet (not shown)

EOS 1100D – key features (from dpreview.com)

  • Superior 12-megapixel image quality
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Canon Rebel T3

ezyfit – An Alternative to Matlab’s Curve Fitting Toolbox

 Computations, Programming Languages  No Responses »
Aug 272011
 

ezyfit can prevent you from buying the Curve Fitting Tool that Matlab does not come with by default. This is how I use it to fit data according to a \sin(2 \theta)^2 function :

x=15:45
y = 30 + 40 * sin( (2*x) * pi / 180 ).^2 + 5*(rand(1, length(x)) - .5)
f = ezfit(x,y,'I(theta) = dC + I_0 * sin( (2 * theta) * pi / 180 )^2');
clf
plot(x,y,'r*');
showfit(f)
dispeqfit(f)

Custom functions can be defined and reused (to speed up) as follows:

Read the full post (134 words, 1 image, estimated 32 secs reading time)

Handle 16bit TIFF Images in Python

 Computations, Programming Languages  9 Responses »
Aug 252011
 

There seem to be quite a lot of problems with 16-bit grey scale TIFF images (especially with the Python Imaging Library – PIL). If you can, you may want to use FITS instead of TIFF. There are good and up-to-date libraries for Python: PyFITS.

For me, however, the FreeImage library works great to read 16bit TIFF images.

About the TIFF Format

Every TIFF begins with a 2-byte indicator of byte order: 0x490x49 (“II”) for little-endian Intel style and 0x4d0x4d (“MM”) for big-endian Motorola style byte order. More common is the Intel style.

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hub teaches git about GitHub

 Computations, Programming Languages  No Responses »
Aug 252011
 

Hub is a useful extension to make git GitHub aware.

catch lines:

hub introduces git to GitHub
and
hub teaches git about GitHub

Installation

brew install hub

Usage

See hub’s webpage for introductory examples and its man page for further reference.

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IPython

 Mac OS X 10.6 Snow Leopard  No Responses »
Aug 252011
 

IPython: Productive Interactive Computing

IPython provides a rich toolkit to help you make the most out of using Python interactively. Its main components are:

  • Powerful interactive Python shells (terminal- and Qt-based).
  • Support for interactive data visualization and use of GUI toolkits.
  • Flexible, embeddable interpreters to load into your own projects.
  • Tools for high level and interactive parallel computing.

Installing IPython on Mac OS X is easy when you already have brew and pip on your system (see my other blog posts Homebrew instead of MacPorts and Python 2.7 on Mac OS X on these issues). So run:

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Get a CLEAN installation of OS X Lion

 Mac OS X 10.7 Lion  No Responses »
Aug 252011
 

There had been some concern that users can’t perform a clean install of Mac OS X 10.7 (Lion) as the upgrade comes without any physical media. You can, however, install Lion as an upgrade of your existing system first. The OS X Installer automatically creates a “Recovery HD” partition on your hard drive, just in case something goes wrong. The partition contains just two tools: Disk Utility and the ability to run the Lion installer. To access this recovery mode, hold ⌘-R while your computer is starting up. Use Disk Utility to erase your hard drive, then run the installer to re-download and install Lion. When you’re done, you’ll have a clean install of Lion.

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Use the Python Module MacFSEvents to Monitor Directories for Changes on Mac OS X

 Mac OS X 10.6 Snow Leopard, Programming Languages  1 Response »
Aug 232011
 

MacFSEvents is an up-to-date solution to monitor directories for changes on Mac OS X when using the scripting language Python. It is a binding to FSEvents, Mac OS X’s filesystem monitoring framework.

Install MacFSEvents

pip install macfsevents

Quickstart

from fsevents import Observer, Stream

def file_event_callback(event):
    """This is the function being called when an event on a file is detected."""
    print "Mask: %s, Cookie: %s, Name: %s" % (event.mask, event.cookie, event.name)

observer = Observer()
observer.start()
stream = Stream(file_event_callback, '/Users/', file_events=True)
observer.schedule(stream)

### Watch how your callback function is being called when files in the /Users dir are changed

# Before your Python program exits, you must stop the observer:
observer.unschedule(stream)
observer.stop()
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Make RS232 Serial Devices Accessible via Ethernet

 Networks, Other Hardware  1 Response »
Aug 222011
 

Standards

The RFC 2217 standardizes the transmission of serial connection data via Ethernet, allowing to change remote serial port parameters (such as speed, parity, stop bits) over TCP using NVT (Network Virtual Terminal).

Implementations

Connection between your serial device and the Ethernet

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