Innovative Uses

Capturing Monarch Metamorphosis in Logger Pro

Ben Carter, a 12-year-old from Nashville, TN, captured a beautiful time-lapse video of a monarch caterpillar pupating into a chrysalis using Logger Pro and a ProScope HR camera (order code BD-HRB, $275).

After planting milkweed obtained from www.livemonarch.com, the monarch caterpillars began showing up in their yard. Ben used the 1-10X lens on a ProScope HR digital USB camera connected to a laptop computer running Logger Pro to capture this video, then shared his results with us. Show it to your own students, or let it inspire you to take your own unique video.

Logger Pro video of a caterpillar pupating into a chrysalis

Download the Logger Pro experiment file and movie (66.5 KB ZIP)

Creative Classroom Solutions

Lab modification gives students more hands-on experience

Peter O'Connor, a teacher from Boonsboro High School in Maryland, described a situation facing many teachers—lots of students and only a few computers.

"Having used Logger Pro for many years dating back to the ULI days, my school has been happy using it in our labs. However, as class size increased, we have had issues with maintaining a small lab group size for each lab. This is a large issue when it comes to doing Vernier labs with computers.

We only have 8 computers in each classroom and try to do many labs with 24 students or more. One of the hardest labs to accommodate is Vernier Lab 24a "Acid-Base Titration." This year, we decided to find a new way to have more groups or individual students work on their own setup instead of having larger groups for this lab.

In order to accomplish this, a modification to Lab 24a was made. This modification uses one LabPro device with two pH sensors to perform two different titrations at the same time. This allows us to have two smaller groups (or individuals) to be next to each other with their own buret performing the experiment.

This year, we were able to do this lab with almost every student doing their own titration, which allowed them to get a better hands-on understanding of the material, and less time watching others do an experiment."

Using this custom file, two groups can run their titration independently, and the only part of the experiment that must be coordinated is the moment when a reading is recorded. Each group has its own data set, graph, and meter on the computer screen. The data can be separated later, if desired, or shared by the two groups.

You can download Peter's custom Logger Pro file, titration-groups.zip (4.51 KB ZIP)

Hot House

Investigating Insulation with Vernier's Infrared Thermometer

Clarence Bakken, a retired physics teacher from California, explored insulating capabilities of different wall materials. Clarence used an Infrared Thermometer (order code IRT-BTA, $159) to study the rate at which heat is transferred through the walls in a model house. He used a simple cube that students built out of wood, glass, or plastic. During the activity, students investigate basic concepts in heat transfer.

Download this sample activity (105 KB PDF)

How Do You Dim an LED?

Have you ever seen an LED-based headlamp that has selectable brightness? Sometimes the brightness change is from turning on more or fewer LEDs, but sometimes the individual LEDs seem to change brightness. How does this work? Usually when you reduce the voltage across an LED, it just goes out. We looked into this question using a Vernier Light Sensor and a LabQuest. You could do this with any visible light sensor and a computer or calculator interface.

The first clue was an observation: When dimmed, and when moved rapidly across the eye's field of vision, the LED leaves a flash trail. When at full brightness, the eye just perceives a solid streak. Could the headlamp be built so that the LEDs are pulsed? This suggests an experiment: Measure the light intensity as a function of time for a dimmed LED light.

What would be a reasonable data-collection rate and duration? Well, we know from looking at the light that it looks more or less steady to the eye, so it must be doing something very quickly. A television refreshes the screen at about 30 Hz, and that sometimes appears to flicker. The LED doesn't visibly flicker in standard use, so it must flash faster than that.

As a starting guess, then, how about taking data at 5000 Hz for a tenth of a second? If we need to change that later, we can. Here's what we saw, after adjusting the time displayed to 0.02 seconds:

Comparison of light intensity for full brightness, always-on settings and the medium brightness pulsed setting

Aha! On high, the LED stays on; but on the mid-level setting, the LED is going on and off at some 400 Hz! What happens if we switch down the brightness a little more? Same parameters, new graph:

Comparison of light intensity for full brightness, always-on settings and the low brightness pulsed setting

Here we see that the brightness is about the same when the LED is on, but that the LED is just not on as much of the time. In technical terms, the duty cycle is lower. When the LED is off, it is not consuming energy from the battery. We get less light, but the battery will last longer.

So, this headlamp manages to have a lowpower, battery-saving mode by flashing the LED on and off. Said another way, the device uses pulse-width modulation to alter the power. It would be hard to see or understand this behavior without data-collection tools being used to extend our senses.

Extension questions:

• Does the average power used by the headlamp scale with the duty cycle of the LED, or is there some significant overhead to perform the modulation?
• How does the pulsing sleep light on some computers work?
• Does it also use pulse-width modulation?

Great Ideas from The Physics Teacher

As usual, The Physics Teacher has been full of good ideas for experiments and demonstrations using our products. Here are some examples:

• "Is It More Thrilling to Ride at the Front or the Back of a Roller Coaster?" by Stefano Alberghi, Alessandro Foschi, Giovanni Pezzi, and Fabio Ortolani (all of Italy), December 2007. They used our equipment to do a thorough study of the accelerations involved.
• "Measuring the Forces between Magnetic Dipoles" by Lisa E. Gayetsky and Craig L. Caylor (Westminster College, PA), September 2007. They use a triple-beam balance to measure the forces, but the experiment could be done more easily using a Dual Range Force Sensor. You can also use our new Rotary Motion Sensor to measure the position. You could also use an Ohaus balance.
• "Acoustic Measurement of the Potato Cannon Velocity" by Michael Courtney and Amy Courtney (Ballistics Testing Group, West Point), November 2007. They used a LabPro and our Microphone to measure the time the potato takes to travel down the barrel and then an additional 10 meters. This allows an accurate calculation of speeds.
• "A Simplified Adiabatic Compression Apparatus" by Michael J. Moloney and Albert P. McGarvey (Rose- Hulman Institute of Technology, IN), October 2007. This "Apparatus for Teaching Physics" article explains how to make an inexpensive adiabatic compression apparatus out of a plastic bottle and our Gas Pressure Sensor.

More Innovative Uses

Doing something innovative in your classroom? Send us your ideas for innovative uses of Vernier data-collection technology, and we might publish your ideas in a future print or electronic newsletter or on our web site.

Include your original data and images of the experiment setup. (Images that include students will require signed release forms prior to being published.) If we choose to publish your idea, we will send you a $100 Vernier gift certificate. Send innovative uses to innovativeuses@vernier.com

Read more innovative uses such as accelerations in snowboarding, chemistry of bathtub tings, and more at www.vernier.com/innovate