Slashdot Mirror

Solar powered chargers in the aftermath of a hurricane?
It'll be days after a hurricane before there's a clear day.
Solar panels work poorly on cloudy days ... those on my roof generate about 5 to 30 percent compared to full sunlight.

Solar panels work way better on cloudy days than you think.
With a heavy over cast sky, most solar panels still yield 47% of their maximum output.
With frequent heavy dark clouds, like a impending storm, the yield is 71% on average.

Its a simple engineering problem to size the solar panel and the batteries for the typical number of consecutive cloudy.

http://www.vernier.com/ makes some outstanding equipment at assorted prices. The Loggerpro software (free 30-day demo, 190 bucks for an unlimited site license), combined with a data logger and a couple instruments (e.g. thermometer and ph meter), total cost maybe...400 dollars...would allow you to run a demonstration experiment, gather the data, distribute it to the students, and then have them analyze it on their own copies of the software (which includes a variety of analysis/graphing/statistical tools). They have a bunch of lesson plans on-line, too.

Some details for those that are curious:
The TI-84 Plus calculator has a USB on-the-go port, meaning it can act as either device or host. Unfortunately the calculator's operating system has no provisions to allow it to connect, as host, to anything other than another calculator or a Vernier data collection thingie. The calculator has a mini-USB port, so a mini-A to A-female adapter cable is required to connect most devices.

I wrote a piece of software, usb8x, which configures and controls the calculator's USB port for use with other devices. It contains the low level USB host (think root hub) driver, and higher level drivers for: mice, keyboards, gamepads, EasyTemp (one of the vernier thingies mentioned above), Silverlink (a TI connection cable), and mass storage devices. The mass storage driver (and msd8x) was started by Michael and finished by Brandon.

The software this article mentions, msd8x, is a UI to access the mass storage driver. It contains a file browser so you can import/export files, and run programs from the drive. The raw read speed via usb8x from a flash drive seems to max out at about 130 KB/s. Reading data from the file system is a bit slower, maxing at about 80 KB/s. Writing data to a file is significantly slower, anywhere from 5 to 40 KB/s, depending on if the file needs to be grown (and on the sectors per cluster and the speed of the flash drive). I'd say the speeds aren't bad considering this is running on a 15 mhz Z80 processor.

Anyhow, I can't speak for Michael or Brandon, but I worked on the USB stuff because I found it to be fun. There are practical applications for those of us that use graphing calculators, but regardless, I don't think that's a requirement for a cool hack. Anyhow, I hope you enjoy it if you have a TI-84 Plus, and that we've provided some good fodder for the usual witty repartee otherwise.

-Dan Englender

...light enough to carry around???? I even have problems carrying around my calculator's keyboard, and that's designed to be portable.

Mod grandparent funny. Or troll. 'Cause it's definitely not insightful.

Take a regular TI graphing calculator (you might have one already from high school or college) and add the TI Keyboard. If you have a computer uplink of some sort for the calculator (either a GraphLink or on-board USB for the newer models), you can transfer your documents to MS Word.

(Vernier's not the only source; they're just one of the cheaper ones. TI doesn't sell the keyboard directly anymore.)

How about one of these attached to one of these? Together you are looking at about $500 but compared to the alternative ... Dig around on thier site they even have accelerometers and other neat stuff. I have used thier software and hardware it's good stuff and the people at the company are friendy and helpfull.

How about one of these attached to one of these? Together you are looking at about $500 but compared to the alternative ... Dig around on thier site they even have accelerometers and other neat stuff. I have used thier software and hardware it's good stuff and the people at the company are friendy and helpfull.

How about one of these attached to one of these? Together you are looking at about $500 but compared to the alternative ... Dig around on thier site they even have accelerometers and other neat stuff. I have used thier software and hardware it's good stuff and the people at the company are friendy and helpfull.