Humble Hubble
Team 18:
Evan Foote, Doug Wile,
Tim Brown, Derek Pesyna
Background: http://apod.nasa.gov/apod/image/1302/ngc1763_lake_1600.jpg
Abstract
The proposed project is a self-aiming
telescope. This telescope will obtain
its global position and the local time
via GPS. It will then automatically
orient itself to point at a user selected
target (star) using a variety of onboard
sensors.
Background: http://apod.nasa.gov/apod/image/1302/ngc1763_lake_1600.jpg
PSSCs
• An ability to establish a coordinate system
based on the telescope's absolute global
position via a GPS chipset, and relative
orientation based on an accelerometer and
electronic compass.
• An ability to compensate for combined
variations in the Earth's gravitational and
magnetic field, and variations in telescope
geometry and mounting configurations via
electronic user calibration.
Background: http://apod.nasa.gov/apod/image/1302/ngc1763_lake_1600.jpg
PSSCs
• An ability to retrieve celestial coordinates and
targets via Bluetooth from an external host.
• An ability to automatically move and point the
telescope at the designated target using feedback
loops from integrated motor encoders.
• An ability to allow the user to manually override
the telescope's target coordinate using an
onboard electronic control interface, and to
display information regarding headings on an
onboard LCD.
Background: http://apod.nasa.gov/apod/image/1302/ngc1763_lake_1600.jpg
Block Diagram
Component Selection Rationale
• All on-board sensors are surface mount and 3-axis.
• GPS switched to on-board antenna, but not
Bluetooth
• CPU selection rationale:
Microprocessor
PIC24FJ64GB106-I/PT -
S912XDG128F2MAL -
Microchip
Freescale
Program Memory (Flash)
64Kb
128Kb
I2C Bus
3 busses
1 bus
I/O Pins
52 pins
91 pins
PWM Channels
9 channels
8 channels
UART channel
Yes
Yes
Operating Voltage
2.0-3.6V
2.75-5.5V
Cost
$6.26
$7.22
Packaging Design
Packaging Design
Schematic: Main Board
Schematic: Aux Board
Focus on Motor Control
PWM Signal
Brake / Coast
Enable (High Z)
Focus on 3.3V regulator
ON / OFF
interrupt
DPDT
Latching Switch
Hold Circuit on
Need to add headers
Schematic: Sensor Breakout Board
PCB Layout
Main Board
Rotary encoders
Auxiliary board
headers
Sensor board
headers
RS232 line
driver/receiver
PIC micro
LCD header,
shift register
VEX encoders
PCB Layout
Auxiliary Board
5V, 3.3V, GND
Bluetooth + GPS
headers
Bluetooth module,
50 ohm antenna
5V, 3.3V voltage
converters
GPS receiver
H-bridge +
power headers
H-bridges,
associated logic
PCB Layout
Sensor Board
Gyroscope
Accelerometer
Compass
I2C + power
headers
Errata
• VDD/VSS for I2C and VEX on main board
• Replace temporary headers with real headers
• Change 100uF capacitor from SMD to
through-hole on aux board
• Unconnected pins on microcontroller, sensors
• Make rotary encoder pads/hole larger
Software Design (Initialization)
Start
Init.
Move to
point North
Select calb.
target
Turn on
GPS.
Get reading
Turn on
Bluetooth,
Connect
Telescope
points to
calb. target
Accel,
compass
reading
Send
GPS/time
data to
Android
Move to
level
position
Android
calcs
calibration
targets
User
centers
telescope
on target
Init.
Done
Software Design (Main Loop)
Start
Main
Get target
from
Android
Move to
target
Wait for
new target
Project Completion Timeline
Week
Starting on Evan
2/25/2013Nothing
3/4/2013PCB parts feedback
3/11/2013Support
3/18/201340% PCB Populated and tested
3/25/2013PCB populated and tested
4/1/2013PCB debugged
Tim
Doug
Derek
Blink LED
Aggregate Star data
Simple GUI
I2C
I2C
Exams
Spring Break
Test software/
software design
Test software/
software design
Low level
development done
Spring Break
Build Mount
Bluetooth over
android
Android app
done
Android wiggle
room
Support Fist
Support Fist
high level software
development done
4/8/2013
WRAP UP ALL THE THINGS
4/15/2013
DEBUG ALL THE THINGS (and write the manual)
Questions?