Near Space Engineering

The NASA Ames Research Center is responsible for various cube satellites, suborbital experiments, and high altitude balloons. The goal of this project is to design a new revision of a circuit board that both enables a modem to connect to the internet and supports auxiliary equipment for NASA’s activities.

Background
Idaho Near Space Engineering teams work closely with NASA Ames to design and test satellites for suborbital missions. The aim of this project is to create a low‐power, general‐purpose communications and power management board for future space flights and high altitude balloon launches.

Deliverables
Design and program a power board. The board would at minimum support an Iridium 9603 data modem, a camera, and have enough general purpose output to drive other miscellaneous equipment such as a cold gas system.

Specifications
The following table contains the specifications for both the new revision being developed and the old revision.

Dip Trace Software
Dip Trace is used to design a printed circuit board (PCB) layout. A PCB electrically connects all the necessary components in a compact space.

Intel Edison
Originally this project was to use the Intel Edison as a processor for the telemetry board. It contains a high-performance, dual-core CPU and a single-core microcontroller that supports complex data collection in a low-power package. It will no longer be needed as a part of the power board.

Overview
The purpose of this board is to be an efficient, low-power support device that performs maintenance functions while the rest of the satellite is sleeping. It has a central microcontroller in a web of low-power peripherals that can be activated at need but remain sleeping otherwise. It will have an Iridium short-burst data modem for communication with the ground and an xBee for gathering data from wireless sensors. IO expander peripherals are used when possible to leave the microcontroller’s pins and serial buses free for communicating with external devices

Iridium Modem
The Iridium 9603 is designed to be integrated into a wireless data application with other host system hardware and software to produce a full solution designed for a specific application or vertical market. For this board, it will be used to long range broadcast the data collected by the various sensors.

Series 1 XBee
The XBee module requires minimal power and provides reliable delivery of data between devices. It will be used to locally broadcast the data collected by the various sensors.

Battery Connector
The 9155 MOBO 2.5mm Pitch Right Angle Battery Connector is rated at 3 amps. The connector’s design is small and compact to minimize its profile yet functionally stable having a contact point at 2.20mm above the PCB.

Battery Charger
The LTC 4000-1 is a controller that converts many externally compensated DC/DC power supplies into full-featured battery chargers with maximum power point control. The LTC4000-1’s battery charger includes: accurate (±0.25%) programmable float voltage, selectable timer or current termination, temperature qualified charging using an NTC thermistor, automatic recharge, C/10 trickle charge for deeply discharged cells, bad battery detection and status indicator outputs. The battery charger also includes precision current sensing that allows lower sense voltages for high current applications.

Thermocouple
The ADS1118 16-bit Analog-to-Digital Converter with Internal Reference and Temperature Sensor component will be used to sample temperatures for two K-type thermocouples. Because the thermocouples are used to measure skin temperatures during orbit and reentry, large measurement ranges are important.

H-Bridge Motor Driver
The DRV8835 has two H-bridge drivers, and can drive two DC motors or one stepper motor, as well as other devices like solenoids. The output driver block for each consists of N-channel power MOSFET’s configured as an H-bridge to drive the motor winding. An internal charge pump generates needed gate drive voltages.

The DRV8835 can supply up to 1.5-A of output current per H-bridge. It operates on a motor power supply voltage from 0 V to 11 V, and a device power supply voltage of 2 V to 7 V.

Buck Regulator
The BD86120EFJ is synchronous buck converters. The device integrates power MOSFETS that provide a each maximums current output current continuous load current over a wide operating input voltage of 4.5V to 18V. Current mode operation provides fast transient response and easy phase compensation.

Solar Panel Connections
Solar panels will be mounted perpendicular to the board on all four edges. They will have bare copper pads, ground and power, running down the center. The power board will have spring-loaded connectors on each edge that will draw power from the pads on the back of each solar panel.

Overview
The software for this circuit board will need to facilitate a number of housekeeping and communication tasks. Our code needs to collect sensor data from the thermocouples, IMU, barometer, batteries, and solar panels. The software must then be able to broadcast the data via the Iridium (long­range) and XBee (short­range) modems. In addition to broadcasting the housekeeping data, the software must also be able to interpret incoming commands from the Iridium modem. These commands will include tasks such as disabling power outputs and temporarily delaying Iridium transmissions.

The software has been broken down into individual tasks that will need to be implemented. There is existing code for certain tasks that will be modified accordingly.

Document Archive
Meeting Minutes (Fall Semester) Meeting Minutes (Spring Semester) Client Interview Design Review Detailed Design Review Final Report