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Tuesday, March 27, 2012

New layout

After way too much time with the same layout, finally and in sync with Blogger restructuring and connection to Google+, I present you with a bit of a nicer look, which is at least is clearer for reading. Stay tuned, as some new posts are on the pipe, with updates on various topics, such as:
  • Geiger Counter - full schematics and firmware source code will soon be posted;
  • Time Lapse Photography - some new scenes of nature at its best will soon be made available.

Saturday, March 24, 2012

Simulation mode for the Geiger Counter



While obtaining samples of materials radioactive above background is not an easy task (fortunately for the sake of human health), I had to find a way of testing the dose measurement algorithm in a different way. As I have explained in a previous post, the device is divided in two modules: a UI module, and the detector device. Each has its own digital logic, and communicate with each other through an I2C bus. As such creating a simulation mode would be a simple mather of programming a new function in the detector that would allow randomly spaced pulses to be generated, instead of being triggered by the Geiger tube. This have been done simply by using the Atmel standard libraries random() function. Using the interrupt generated by the watchdog timer overflow, the following code is executed periodically:

Saturday, March 10, 2012

More in Time Lapse

And to add to the party, another bit of playing around with time lapse. This time zoomed in on the Tagus river, and obtained this interesting sequence. To achieve it, the intervalometer was set to take a picture every 10 seconds. Again, automatic settings such as ISO sensitivity and aperture were chosen. Only the focusing was kept manual.


Sunday, March 4, 2012

The timelapse intervalometer - the technology behind the device

With the results having been posted in a previous post, it is now time to flesh through the details that led to the creation of this simple yet useful device.

I started with the optimism that my Fujifilm S9600 camera would have some form of remote control possibillity other than the mechanical shutter release that is supported in the shutter button itself.

Saturday, February 25, 2012

Time lapse shooting - moving into more professional results...

While the first videos seemed pretty cool in spite its mediocre quality (maybe because of the time domain wonder of perceiving things that we normally wouldn't given the different time scale we live in), now I had to move one step further.

The idea was to use a better camera, one offering photographic quality in every single frame.

Friday, January 27, 2012

From morning until dawn - and entire day described in seconds

Time lapse video sequences can render exciting results, for the visual impact these provide. While simply being a sequence of frames more separated in time than in a conventional video, once played back at the rate the human vision considers smooth (30 frames per second) these provide a view of the world that a human cannot easily perceive directly, given the comparatively fast rate at which he summarizes and retains information. For instance a cloud in its pass has very complex yet slow changes in shape and trajectory. These are very hard for average humans to perceive, memorize and mentally reconstruct as an animated sequence of events. In general, slow changing processes are inherently hard for humans to characterize in its dynamic nature.

As such it is not surprising that a video containing nothing more than a reproduction of the real world can be appreciated by humans as being somewhat surreal, when simply the only difference is the rate at which information is sampled and later reproduced.

The first video contains about 20 hours of footage shrunk to 32 seconds. It reveals one angle of the Almada city at the south of Lisbon, where part of the 25 de Abril bridge and the Cristo Rei can be seen. It is a typical winter day in Portugal, where the fog floods the morning and a passing of dense clouds fulfills the entire afternoon. This typical day is however solitary in a atypical winter month padded with bright sunny days and mild temperatures.



The second video taken during the 27th January 2012, reveals a clear night transition to a bright winter day in the city of Almada, just south of Lisbon the capital city of Portugal. At the bottom right, the horizon is cut by a huge rectangular crane belonging to a long time decomissioned shipyard.Its name was Lisnave and would once be an important maritime reference for large ships and oil rigs which would stop by for major repairing and overhauling.

Wednesday, December 21, 2011

LENA - Now featuring dose measurement

The DOSE feature discussed in the previous post is now done. Taking into account the GM tube characteristics, a realistic measure of radiation dose in uSv/hour is now being calculated, based on the single event rate. From the information obtained on the internet regarding the SI-39G tube, the value of 0.00049 uSv per pulse was taken into account for the calculation of the dose.

Additionally, another mode usually found in most Geiger counters and dosimeters is the CPM (Counts Per Minute) mode. It provides a relative measure (that is of course GM tube dependent) of the radiation exposure, based on the ammount of particles detected by the tube. In this case these can be either Beta particles with more penetrating energy, and Gamma photons. Alpha particles cannot be detected by this particular tube (the SI-39G).