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Detailed Design
Junction Box
The Junction Box serves as a node for all the leads from the solar panels to be brought together and condensed to power lines for each battery. The Junction Box will also house a telemetry board (linked to the C&DH system) to take voltage and current readings for each solar panel, as well as a thermistor for each side of the satellite and two thermistors per battery box.
The junction box will also act as the entry point for the external connections for ground battery charging and battery temperature monitoring.
Voltage Regulator/Battery Charger
A voltage regulator will be used to regulate the voltage charging the batteries. The power from the solar panels will vary as the satellite rotates. Some cells will be entirely in the dark, some will be in the light. The regulator will ensure the voltage supplied to the batteries does not fall below the voltage of the battery itself. Each battery will have its own regulator for redundancy. The voltage regulator will be located inside the Battery Box, on a printed circuit board (PCB).
Battery ChargersSwitches
The batteries will be controlled using electronic switches. There will be a switch between each battery, regulator, and distributor - two switches per battery per line (for redundancy). These switches can be used to isolate any battery from the system, or allow one battery to charge while another provides power to the distribution bus. Switches will be placed between each non-vital payload and the distribution bus. Although the power to the payloads is regulated, the switches will act as a further guard against surges. There will also be a battery bypass switch that can be used in the event of failure of both batteries to allow the distribution bus to run off of the solar array power. Various FET switches are currently being looked into.
Distribution Block
The payloads require voltages of +28, +15, +12, +8, +-9, +5.2, +5, and +4 V. The specific tolerances for each payload are listed under Power Requirements. Since the batteries will only provide a single voltage, the power from the batteries must be divided up before it can be used by the payloads. This will be done through the distribution block. The distribution block will be composed of several DC/DC voltage regulators. Where off the shelf DC/DC regulators are unavailable, another voltage within that payloads voltage tolerance will be used. Each regulator will have a remote operation function allowing the C&DH to turn the power to a payload on or off. The regulators that make up the Distribution Block will be on the same PCB as the Voltage Regulator. The regulated voltages will then feed out from the PCB and Battery Box to the payloads through a DB-25 connector .