Power Distribution
Control Unit
Team MADD
Michael Davies
Andrew Mountain
Dan Hoang
Daniel Brink
History/Background
Citizen Explorer
Citizen Explorer-I (CX-I)
• Designed and built by students at Colorado Space Grant
Consortium in Boulder.
• The mission design allows K-12 schools around the world to be
involved as ground stations available to receive science data and
telemetry from CX-I.
• Two instruments, an aerosol meter and UV detector, will be used
by the K-12 students to take measurements on the surface of the
Earth.
• A low level of artificial intelligence will be supplied to the
spacecraft through the use of the Automated Scheduling and
Planning Environment (ASPEN). ASPEN is used to maintain a
spacecraft schedule in order to achieve the objectives a mission
operator would normally have to complete.
MADD Project Purpose
Design a new Power Distribution Control Unit (PDCU) for
the Colorado Space Grant Consortium’s Citizen Explorer
spacecraft. The new PDCU must meet CSGC’s reliability
requirements and integrate as a functional subsystem the
satellite.
MADD Objectives
Software Functionality
• Control the power distribution to seventeen component systems of
the spacecraft
Receive desired state commands from the flight controller
and ensure that the component system is in the desired state –
otherwise send flight computer an error message
Store the state of each relay into memory every 5 seconds, in
case of a power failure
• Check for proper functionality of flight computer
• Authorize digital signature from flight controller, otherwise
provide a power pulse to restart flight controller
• Relay the status of the PDCU through voltage, current and
temperature readings
MADD Objectives
Hardware Functionality
• Using a 12V source, provide four alternate voltage power
buses
• Secondary Objective is to design the 24V boost converter
• Using relays that receive a signal from the micro controller,
control the power distribution to seventeen component parts of
the system
• Fit the dimensions – 7.15" X 7.65" X 2.7"
• Build wire wrapped prototype
• Transfer to PCB
MADD Objectives
Reliability
• Nature of project reliability is a critical concern
• Included in design should be ability to check proper
function of system
• Devise a system for testing to prove reliability
Expand the test to use LED or other display
devices
• Emphasis on very tight, consistent and reliable code
Flight
Computer
Battery
PCB
PDCU Micro
Controller
Power
Converters
Thermistors
Relays
Critical
Decoder
ADCS
COMM
Science
CPU
RS485
Micro
Controller
Flash
Memory
Power
Converters
PCB
Therm
Therm
17 Relays
LED
LED
LED
LED
Hardware
Micro Controller
• Manufacturer: Microchip Technology
• Part number: PIC16C877
• Micro controller specified by CSGC
• Choose the 877 over 77 because of the flash memory
incorporated into the chip
RS-422/485 chip
• Manufacturer: Maxim Integrated Products
• Part number: Max3082E
• Provides communication between micro controller and
flight computer
Hardware
RS-232 chip
• Manufacturer: Maxim Integrated Products
• Part number: Max208
• Provides mechanism for interface with PC serial
port, can be converted to RS-422/485
Relays
• Manufacturer: Crydom
• Part number: DM063
• Part specification from CSGC
Hardware
Thermistors
• Manufacturer: Yellow Springs Instrument
• Part number: YSI44901
Memory
• Flash or FRAM
– Looking into the necessity of memory in addition to the
memory on the micro controller, depends on program
storage requirements
– FRAM more stable for space conditions
– Decision to be made within a week
Hardware
Power
• 24V boost converter
– CSGC design
• Power Buses all capable of 5 watts
–
–
–
–
15V converter
-15V converter
5V converter
12V converter
Risks/Contingency
Risks
• Unfamiliar technology
• Part availability
• Time constraints
• Funding
Contingency
• Help from Space Grant
• Order parts early
• Drop PCB
• UROP/Space Grant
Project Schedule
Divisions of Labor
•
•
•
•
Mountain: PCB Design
Brink: Hardware Layout
Davies: RS422/485 Protocol, PIC Programming
Hoang: RS422/485 Protocol, PIC Programming