Our final project is the CUSat Diagnostic Board (CUDB). This board will be used for monitoring CUSat system health as well as performing various functions allowing for easy integration and debugging of CUSat components.
1.1 CUSat
CUSat is the Cornell satellite team's entry into the Nanosat-4 competition sponsored by the Air Force Research Labs (AFRL). A significant milestone for CUSat is entering the "flat-sat" stage of manufacturing. This is where all satellite components are electrically connected on a clean-room bench, but not structurally integrated into the satellite frame. To make flat-sat debugging and integration easier, we have developed the idea of the CUSat Diagnostic Board (CUDB).
1.2 Report Layout
This project involves the combination of many circuit systems and many software systems. We have split up the report into several sections. Sections 3 and 4 of this report contain only design details. They do not contain the results of our tests and experiments to verify the functionality of the CUDB. Section 5 details our results of testing the various systems. Section 6 contains our conclusions.
2 CUDB Design Overview
The CUDB has the following functionality (each one of these functions is discussed in detail later in this report):
Current sensing of the CUSat power bus
Charge and discharge the CUSat batteries
Supply CUSat with a source of power
Ability to reprogram all microcontrollers on the satellite without have them removed from flat-sat
Interface with a PC for human control and data observation
The design of the CUDB is such that we can "make life easier" for the other subsystems as they begin integrating their hardware into flat-sat. For example, the first subsystem to have hardware in flat-sat is the Power subsytem. The Power subsystem harnesses energy from solar cells, which will not operate while we are in lab. As such, the CUDB provides the 18.5 volts that the Power subsystem expects from the solar cells - letting the Power team test their hardware. Further, the Power subsystem has a battery charging circuit which CUDB can power. And, CUDB provides a method of discharging the batteries (normally done by running actual CUSat hardware in flat-sat).
For the reasons outlined above, the only way for CUSat to complete a finished product with the project's strict schedule is to have the CUDB operational by the time flat-sat is fully developed.
Most of the part selection has been completed by CUSat members Kris Young and Michael Austin. The basic PCB design was finalized by CUSat member Tyler Orchowski, and reviewed by Eric Brumer & Jiangang Shi. Our project entails:
Populating and testing the CUDB as a standalone device
Writing all of the CUDB software (MCU and the graphical user interface [GUI])
Interfacing the CUDB with:
CUSat subsystem hardware
CUSat data bus
CUSat batteries and power subsystem
The CUDB GUI
2.1 Specifications
Since CUSat is being developed for the AFRL, all components (including support equipment such as the CUDB) must comply with select military specifications (MIL-SPECs). Here are some specifications which must be followed for CUDB development:
MIL-STD-1540D - "Product Verification Requirements for Launch, Upper Stage, and Space Vehicles"
KHB 1700.7C - "Space Shuttle Payload Ground Safety Handbook"
DOD-W-83575A - "General Information for Wiring Harness, Space Vehicle, Design and Testing"
A complete list of the military and department of defense specifications is not available to be published due to International Trade and Arms Regulations (ITAR) restrictions. However, if the reader is interested in mil-specs, please contact Eric Brumer for more information.
2.2 Parts List
Custom 2-layer Printed Circuit Board (PCB)
Atmel Mega128
16MHz Crystal
LM3480IM3-5.0 18.5V, 5V Voltage Regulator
LM4040 Zener diode voltage shunt
MAX3083, RS-485 Driver
MAX3322, RS-232 Driver
MAX4372T, Current Sense Amplifier (3x)
MIC442A, Power FET Drivers (5x)
Si4410DY, FET Switch (5x)
1101M2S3CQE2, Mechanical on/off switch
808 Circuit Breaker (3x)
AD7376-10k, High precision digital potentiometer
Various capacitors, resistors and resistor packs
Various LEDS for debugging and display information
Link: http://instruct1.cit.cornell.edu/courses/e...b229/index.html
1.1 CUSat
CUSat is the Cornell satellite team's entry into the Nanosat-4 competition sponsored by the Air Force Research Labs (AFRL). A significant milestone for CUSat is entering the "flat-sat" stage of manufacturing. This is where all satellite components are electrically connected on a clean-room bench, but not structurally integrated into the satellite frame. To make flat-sat debugging and integration easier, we have developed the idea of the CUSat Diagnostic Board (CUDB).
1.2 Report Layout
This project involves the combination of many circuit systems and many software systems. We have split up the report into several sections. Sections 3 and 4 of this report contain only design details. They do not contain the results of our tests and experiments to verify the functionality of the CUDB. Section 5 details our results of testing the various systems. Section 6 contains our conclusions.
2 CUDB Design Overview
The CUDB has the following functionality (each one of these functions is discussed in detail later in this report):
Current sensing of the CUSat power bus
Charge and discharge the CUSat batteries
Supply CUSat with a source of power
Ability to reprogram all microcontrollers on the satellite without have them removed from flat-sat
Interface with a PC for human control and data observation
The design of the CUDB is such that we can "make life easier" for the other subsystems as they begin integrating their hardware into flat-sat. For example, the first subsystem to have hardware in flat-sat is the Power subsytem. The Power subsystem harnesses energy from solar cells, which will not operate while we are in lab. As such, the CUDB provides the 18.5 volts that the Power subsystem expects from the solar cells - letting the Power team test their hardware. Further, the Power subsystem has a battery charging circuit which CUDB can power. And, CUDB provides a method of discharging the batteries (normally done by running actual CUSat hardware in flat-sat).
For the reasons outlined above, the only way for CUSat to complete a finished product with the project's strict schedule is to have the CUDB operational by the time flat-sat is fully developed.
Most of the part selection has been completed by CUSat members Kris Young and Michael Austin. The basic PCB design was finalized by CUSat member Tyler Orchowski, and reviewed by Eric Brumer & Jiangang Shi. Our project entails:
Populating and testing the CUDB as a standalone device
Writing all of the CUDB software (MCU and the graphical user interface [GUI])
Interfacing the CUDB with:
CUSat subsystem hardware
CUSat data bus
CUSat batteries and power subsystem
The CUDB GUI
2.1 Specifications
Since CUSat is being developed for the AFRL, all components (including support equipment such as the CUDB) must comply with select military specifications (MIL-SPECs). Here are some specifications which must be followed for CUDB development:
MIL-STD-1540D - "Product Verification Requirements for Launch, Upper Stage, and Space Vehicles"
KHB 1700.7C - "Space Shuttle Payload Ground Safety Handbook"
DOD-W-83575A - "General Information for Wiring Harness, Space Vehicle, Design and Testing"
A complete list of the military and department of defense specifications is not available to be published due to International Trade and Arms Regulations (ITAR) restrictions. However, if the reader is interested in mil-specs, please contact Eric Brumer for more information.
2.2 Parts List
Custom 2-layer Printed Circuit Board (PCB)
Atmel Mega128
16MHz Crystal
LM3480IM3-5.0 18.5V, 5V Voltage Regulator
LM4040 Zener diode voltage shunt
MAX3083, RS-485 Driver
MAX3322, RS-232 Driver
MAX4372T, Current Sense Amplifier (3x)
MIC442A, Power FET Drivers (5x)
Si4410DY, FET Switch (5x)
1101M2S3CQE2, Mechanical on/off switch
808 Circuit Breaker (3x)
AD7376-10k, High precision digital potentiometer
Various capacitors, resistors and resistor packs
Various LEDS for debugging and display information
Link: http://instruct1.cit.cornell.edu/courses/e...b229/index.html