Handy Board Expansion Interface,
Version 2.0

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The HB Expansion Interface

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The Handy Board Expansion Interface plugs into the Handy Board, providing a number of new features:

• Sixteen (16) general-purpose analog inputs.
• Four (4) high-impedance analog inputs, suitable for interfacing with sensitive devices.
• Four (4) inputs for active LEGO sensors (the visible red reflectance sensor and the shaft encoder).

  Three analog inputs from the main board are used to provide these 24 inputs.

• Four (4) outputs for hobby servo motors. Power for the servo motors may be supplied from the main Handy Board battery pack (through a series diode circuit that reduces the battery voltage to a level appropriate for servo motors), or via an external battery pack attached to a screw terminal connector.

• Two (2) transistor outputs, capable of driving 1 amp at 9 volts.

• Connector for the Polaroid ultrasonic ranging sensor.

• User application prototyping area.

The following links provide information on a previous version of the Expansion Board. Note that this earlier version (which was not released widely) included some features that are not planned for the subsequent board (e.g., the PIC programming circuit), and lacked some features that are planned (e.g., the transistor-drive outputs and LEGO sensor inputs).

• Schematic diagram of Expansion Board main circuitry (on-screen display).
• Schematic diagram of Expansion Board PIC microprocessor, programming voltage, and ultrasonic connector circuitry (on-screen display).
• Both schematics as a color PostScript file.

• Expansion Board parts placement diagram (on-screen display).
• Expansion Board parts placement diagram (color PostScript file).

• Expansion Board parts listing (on-screen display).
• Expansion Board parts listing (tabbed version for importing into a spreadsheet).

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