2.3 Technical RequirementsAt the CCE, different technical construction kits and systems are being used which may be suitable for applications to be controlled by Crickets. Among them are kits from ‘Lego-Technic’ and ‘Fischertechnik’. Pneumatic elements from Festo as well as ‘Märklin-Metall’ construction kits may also be introduced in the near future.
Together with self-made equipment (i.e., motors, switches, and lamps of any kind), this means a wide selection of different systems that will not work together at first. Especially the various sensor and actor devices are not compatible with the Crickets. The mechanical interfaces will not fit either.
As a first step towards an integration of at least some of these systems, the electrical as well as the mechanical specifications and properties will have to be tested, verified, and analyzed. Depending on the findings of this analysis, it should be possible to prepare strategies saying which of the systems can be combined, and how they could be able to interact with the Crickets.
The next step will be the adaptation of the various interfaces. While self-made sensor and actor devices can be designed or re-designed to meet certain requirements, purchased parts and especially the Crickets themselves should not be altered. By avoiding any change in the Crickets’ mechanical and electrical structures, it is possible to keep the modules fully replaceable. This means, they are not dedicated to a special application, but can be used in different projects just as well, which is very important for the exchange of experience between the CCE and other members of the Computer Clubhouse Network.
The cooperation within the Network is also the reason for the documentation of this thesis to be published on the Internet. Through the World Wide Web, mentors and kids at all Clubhouse locations will have the opportunity to share our experiences and results. While there are several possibilities how to present this documentation on the Web, readability in all modern browsers as well as easy-to-use navigation facilities should be granted the highest priority.
The central part is the Cricket module. What can be learned about its internal design (i.e., the properties of the processor, the memory, etc.) and its interface specifications? The latter include the IR port, the sensor inputs, and the motor outputs.
Regarding motors, there are many different types from Lego, Märklin, and other manufacturers. The Cricket outputs are only specified to work with the micro motors from Lego. About all other motors, no power ratings are available – important parameters like voltages, idle currents, and stalled currents need to be figured out.
Another challenging aspect is the combination of Crickets with Festo Pneumatic systems, as the electrical devices from Festo (magnetic valves) are controlled by a much higher voltage than the Crickets can provide. The valves’ power consumption will be a key factor to decide on possible solutions.
Some sensor devices are already available. What resistance value do they provide, and what is their range? The answers to these questions will show how new kinds of sensors could be designed to meet the Crickets’ requirements.
Just as important as the electrical interfaces are the properties of the various mechanical systems – the Lego and Märklin systems, for example, are based on very different strategies. Each system’s advantages and shortcomings with regard to easiness-of-use, strength, and compatibility, have to be considered.
Finally, the Cricket programming software is of great importance. As there are different kinds of software (source code programming, and graphical user interfaces), their respective possibilities need to be figured out. Criteria for the evaluation of software could be its set of commands, its flexibility, and last but not least, its suitability for kids.
Since the single elements (e.g., motors, valves, cylinders, metal bars, and plastic pieces) are integral parts of their respective systems, they must not be changed. Thus, no electrical connectors should be replaced by a different type, and especially the Cricket modules must be left in their original state.
Instead of changing existing parts, adapter elements should be placed between the systems. This applies to both electrical and mechanical interfaces. In other words, practical solutions should be found for the following challenges:
For the HTML pages, smaller versions of embedded images should be available to be displayed in the document itself. By clicking on a small image, the full-size version should be displayed separately. This procedure keeps loading times low over the Internet, an the high-detail image is still accessible.
The HTML documentation should be divided into several HTML files. This makes it easier for the reader to print just a part of it and speeds up the display of the pages in the browser. If frames are used, there should not be more than three frames at a time.
All parts must also be accessible with a browser that does not support frames. Basic navigation facilities must be granted for those browsers as well.
For the PDF documentation, no technical requirements are necessary. This file format contains the complete document in a quality that is comparable to the printed version. Included photographs and drawings may be sampled down to 300 dpi.