Shown below is the Micro Beacon II controller board.  The board is a custom built, 2" x 2.75" double sided circuit board.  The board contains the processor as well as the power converter, temperature sensor, packet radio MODEM, and GPS engine. The shiny coating on the board's surface is conformal coat.  The sprayed on conformal coat protects the electronics from humidity and condensation encountered during a balloon mission.

Temperature Sensor National Semiconductor LM60 with 20dB gain through an op-amp to scale to the PIC 18F252 ADC input range.

Radio Interface Standard audio and PTT (Push-To-Talk) interface to radio.

Programming Port In-circuit serial programming port for PIC18F252 processor.  Software developed in C programming language.

Packet MODEM 1200-baud AFSK MODEM for AX.25 packet radio standard.

Power Converter  High efficiency power converter.  Heat sink not required.  Provides multiple output voltages (+3.0 and +3.7) for subsystems and runs from a single 2.8 VDC lithium cell or 2 NiMH cells.

Controller  Microchip PIC18F252 flash memory based processor running at 3.6864MHz.

Flight Data Recorder  1M bit (128K bytes) serial memory for flight data recorder.  10,000 write cycle capable.

All I/O through connectors to allow for ease of installation and repairs.

Industrial temperature range, -40° C to° C.




Micro Beacon II controller board.


Schematic / PCB Layout

For best quality, print the schematic on a single 8½ x 11" sheet of paper in landscape mode using your favorite graphics application.

Schematic (Graphic - GIF)	PCB Layout (Adobe PDF)