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Power Distribution Control Unit Michael Davies Andrew Mountain Dan Hoang Daniel Brink Functionality • Power Distribution Control Unit for Colorado Space Grant’s Satellite Citizen Explorer • Implement commands from the satellite’s flight computer to provide the desired power to the unit’s subsystems • Monitor specified temperatures and power buses Schematic Distribution of Power • • • • 17 – 4-Pin solid state relays Control using 5V logic Direct I/O with PIC Connected with desired voltage Schematic Temperature • Voltage Divider • Maximum range voltage – low power consumption • Analog multiplexer • A/D converter on chip Schematic Power Supplies • Rigorously test power supplies • Power draw on each bus • Concern with noise on 5V power bus – Pi-Filter near each chip that require 5V PCB Board • 4-Layer Board • 2 Parallel 7.15" X 7.65" boards • Through hole parts for stability 7.15" X 7.65" Parts List • • • • • • • • Microcontroller: PIC 16C77 Relays: DMO063 Clock: ACH-20.000MHz Thermistor: YSI44901 12v to 15v/-15v Converter: JR12D15-330 12v to 24v Boost Converter: SI12S24-1250 12v to 5v Converter: LANC1205W5S Flight Computer Interface: RS485/422 Max3082ESH • PC Interface: Max208CN6 Microcontroller Relays Thermistors Temperature Resistance Characteristic 35,000 30,000 Resistance [ohms] 25,000 20,000 15,000 10,000 5,000 0 -40 -20 0 20 40 60 Temperature [celcius] 80 100 120 Flight Computer Interface Serial Communication PC Interface Basic Software Functions INITIALIZE VOLTAGES DELAY CURRENTS TEMPS SEND INFO? Basic Software Functions SET ANALOG SWITCH POS 1 VOLTAGES SAVE VOLTAGE 1 SET ANALOG SWITCH POS 2 SAVE VOLTAGE 2 SET ANALOG SWITCH POS n SAVE VOLTAGE n A/D CONVERSION RETURN Basic Software Functions INTERRUPT RECEIVE TRANSMIT RETURN OTHER? Basic Software Functions RECEIVE READ BYTE SET RELAYS SEND INFO RETURN Basic Software Functions BOOT SEQUENCE CD&H 1 min delay REQUIRED ADCS -extra delay for FC 3-5 sec delay Mnet 3-5 sec delay ARBITRARY Science 3-5 sec delay Deploy Schedule Division of Labor • • • • Michael Davies: Software Andrew Mountain: PCB/Schematic Design Daniel Brink: Hardware layout Dan Hoang: Hardware/Software interfacing Milestones • Milestone 1: Completed Prototype (wire wrap) and interface-able test code • Milestone 2: Completed PCB Design and ready to order (first revision) • Design Expo