Saturday, March 22, 2008

Sky Color Project - What is the color of the sky today?

In this easter, we finished a "non-electronic" project and find no where to post. Hope it is not so off topic here:)

There are few web cameras installed to monitor the weather or traffic conditions online, so what else information can we get from these images? One important thing to us is the color of the sky. It is a sign of weather and also the pollution condition. So this small project comes up.

we developed a program to analyze the color of the images and look for the best blue.

The process includes four steps:
1) Fetching image from the web camera (an automatic web image fetcher is used)
2) Color Segmentation (Masking out the non-sky component)
3) Analyze the blueness (Finding out the best blue)
4) Output a small square image colored in best blue found in step 3

The color segmentation is the most difficult part, the blueness is hard to define. Luckily, we can easily find many digital images nowadays in flickr or other online gallery system. We used the images to train our color segmentation engine and also with some human fine tunings.

We got 365 images from the Hong Kong Observatory (Yes, we live in HK) in the year 2006.
The sky with no blue-like color is ignored in step 4, it happened in cloudy or rainy or dusty day and so you will see a gray or white cloudy sky, i.e. no color captured.

A processed image from step 1 - 3
(Buildings are masked)

A sky color palette is generated for the year 2006 in HK:

- the pink box is the start of the month (e.g. JAN)

In a statistical view, we make a sky color bar chart for each month.

What we can get in this chart?
1) Second half of the year, we get a clearer sky.
2) In August, we have more blue sky days.

Wednesday, March 12, 2008

Wind-Lit ( A wind activated Lamp )

This "wind bell" shaped lamp is called "Wind-Lit", created by There are few LEDs inside the case, when the wind blows that making the bottom place move, it triggers the LED to grow. It is a nice idea to make a growing LED project with wind activation which provides some random effects and most importantly the link between the nature and you. The new version included a solar panel charging in day time, and the LED grows at night time. It is a prefect product for your garden.

It was also demonstrated in a cafe in Japan:

The effect is fantastic:)

Project by

Monday, March 3, 2008

Table Lamp Solar Charger (Solar Charger Test setup)

After studying how to make a simple solar charger, I decide to make a fast prototype to test. I got one solar panel a long time ago, the ratings of this solar panel is unknown. The solar panel will output different voltage and current under different lighting condition, so we have to measure it before use. I measured this solar panel would output maximum 3V under bright sunlight, and output 2V under my table lamp.

Everyone got a table lamp when working in front of the computer, and the light condition will remain considerably constant when compare to the outdoor sunlight condition. It would be easy to make one simple table lamp charger.

The above diagram is my setup, I used the schottky diode (IN5819) to prevent back current flow to solar panel when the lamp is off. The diode is placed between the solar panel and the the battery holder with two AAA batteries loaded. When charging, I measured the forward voltage across the diode is 0.14V which is small when compare to a normal diode.

Initially, the voltage across 2 batteries are 1.7V, after a while the voltage is 1.81V, so it is charging right now. The charge current measured is only 0.12mA.

The current is too small, and not so sure how long it will charge up to 2V:)

Sunday, March 2, 2008

Small 5x7 Dot Matrix LED display

What is 5x7 dot matrix display?

5x7 dot matrix Led display is usually used to cascade together to make a large led matrix display as you see in train station.

(A typical LED matrix display)

The small size of 5x7 dot matrix led display is good for small electronic project, typically the 5x7 dot matrix is used to display one character a time, i.e. 5x7 dot matrix font. In order to use only one 5x7 dot matrix to display information, we have to use the 5x7 dot matrix horizontally. We use the 5x4 dot matrix font instead and of course text scrolling will be necessary.

The KAAS Led flower vase is using the 5x7 dot matrix display for displaying messages.

kaas used one AVR tiny13 and two 74hc595 chips to drive the led matrix, the result is very impressive. The detail information of the LED flower vase is here.

Another interesting project is the Twitter LED scroller Build from davidnin. He used the Arduino board and one 74HC595 to drive the 5x7 dot matrix led. Please check out the cool video:

Another project from us, GIF2LED!
it allows you to convert a gif animation to LED header file to speed up your coding time:)

Check it out:

Another cool tiny message scroller using ATtiny2313 from kalanda: