n the Science Learning in Context (SLiC) project we look at how science learning and investigation can be improved when kids use mobile computers and probes. When we put 20 kids using eMates™ with probes alongside a stream and had them measure temperature, light, pH, and dissolved oxygen, some interesting strains were put on equipment which worked fine when sitting on a lab bench back in school.

We discovered there were too many boxes and cables. The probes were connected to a signal processing box which was connected to an interface box which was connected to the serial port on the computer. Holding all this and a computer while measuring in a stream is sometimes more than a two-student job. The six AA batteries in the interface box ran down too fast and came loose occasionally.

Early in the SLiC project we developed the Concord Consortium Serial Box Interface (CCSBI) and based it on a new inexpensive 8-pin microcontroller. Because the CCSBI is smaller and lighter than the older serial interface, uses a single 9V battery, and consumes very little power, it made mobile investigation more practical. Later we realized we could do better by getting rid of the interface box entirely and making a smarter probe.

A SmartProbe™ combines a sensor, analog-to-digital conversion, a microcontroller, memory for saving its calibration, serial communication, and power-management circuitry all in one small, conve- nient package. The design goal is, given economic constraints, to increase the ease of use and reduce the opportunities for mistakes and failure. SmartProbe features include:

• Remembers its calibration. Using the calibration it reports back to the computer in physical units instead of raw data.

• Uses little power and, when possible, eliminates the battery entirely by getting all necessary power from the computer's serial interface.

• No on-off switch, thereby eliminating a potential source of confusion in the field. Whenever an active serial interface connection is detected it automatically turns itself on.

• A standard three-wire RS-232 serial communication protocol so that it can be connected to the widest range of computing hardware.

• A communications protocol to enable code, commands and data to be passed between the computer and the probe.

• A power source with the capability to record data while disconnected from the computer.

We adapted the older Mac Motion software to work with the CCSR. Additionally, we developed software for an extremely portable computer, the PalmPilot™. The software on the Pilot displays real-time distance, velocity, and acceleration graphs. The CCSR uses a special power saving circuit design so that it can operate continuously for 25 hours on four AA alkaline batteries. This combination makes an extremely portable and powerful tool for exploring the kinematics of motion inside and outside a school.

We're also working on a SmartProbe for temperature that connects to a serial port. We estimate a parts cost of under $10 in 1000 unit quantities. A key element in the low cost is the TMP03 temperature sensor from Analog Devices. This sensor outputs its measurement digitally in a way the microcontroller can measure without a separate and expensive analog-to-digital chip. If we use tiny surface-mount components the circuitry will not take any more room than that needed to house the sensor itself.

With a probe this smart obviously there is a need for smarter probe software - software that would run on any computer platform and automatically start up whenever a SmartProbe is attached.

But that's another article.

Stephen Bannasch is the Concord Consortium's Director of Technology. stephen@concord.org

Spring 1998 | Table of Contents | Library Index | CC Home

Copyright © 1998 The Concord Consortium, All rights reserved. Last updated: 12-July-99
Questions and comments regarding this site can be sent to webmaster@concord.org