Thursday, December 24, 2009

Halogen resistance

If you are curious, the resistance of a 300W type J halogen bulb, the ones you would find in those halogen torchiere lamps, is 3.3 ohms when cold. When it's hot it is 48 ohms, but that's a calculation only based on the wattage.

A warm halogen bulb in the near infrared

Since converting such a torchiere to CFL (but not in this project), I had an extra halogen bulb and debated throwing it out, but I figured they might make a decent power resistor. I used it in a project converting a PC ATX power supply to a benchtop 12V source. It works--but the hassle of cleaning the contacts for soldering, soldering, and placing such a large object in the case was enough to decide buying a power resistor in the first place is probably easier.

Monday, December 21, 2009

Winter Solstice 2009

Happy Winter Solstice.

From taken on 11:54AM (a few minutes past the solstice time) (on campus only)

Chicago is looking as good as 2006!

Enjoy this graph of the date and time of the solstice over the years.

Friday, December 18, 2009

Image of the day: Tethys

The saturnian satellite Tethys, imaged on October 14th, 2009. From the viewpoint of Cassini, the Sun was nearly directly behind the spacecraft when this image was taken.

Click to enlarge

Source: NASA/JPL/Space Science Institute

Monday, December 14, 2009

Martian swirly art

I am sure you've already seen this image from Mars of the swirly traces of dust devils removing the light dust from the darker surface. But here it is.

Click to enlarge to a 2560x1920 version
This is a dune field in a crater just off of Syrtis Major.

Links to other sizes.

Thursday, December 10, 2009

Crescent Earth

The Earth captured from the Rosetta spacecraft as it passed by Earth.
ESA. Taken on 11/12/2009. Click to enlarge.
As seen on the Planetary Society blog.