AA241x
Spring 2015
Adrien Perkins
H A R D WA R E A N D S O F T WA R E O V E RV I E W
168 MHz Cortex M4F CPU 2 MB Flash 4 GB SD card – many many hours of logging
Pixhawk
Wireless Telemetry (3DR Radio)
915 MHz, 100 mW Unique “NetID” for each set Mavlink Protocol
USB Micro
USB
DF13 6-Pin
GPS + Magnetometer
GPS Radio› Needs clear sky view› 5 Hz update rate
Magnetometer› Provides heading estimate› Keep away from high power electronics (speed controller)› NOTE THE ARROW!!› If you reposition it, always good to recalibrate it
DF13 6pinGPS
DF13 4pinMAG
Airspeed Sensor
Measures difference between static and total pressure to determine airspeed
Wind will affect speed reading
Silcone Tubing
DF13 4pin
Power Module
Record current and voltage from battery Powers pixhawk, radios, receiver Does not power servos!
DF13 6-Pin
Safety Switch and Buzzer
Safety Switch› Physical “hardware” arming switch› To arm: press and hold for 3 seconds
(should go from slow flash to fast flash)
› Allows for “software” arming to occur• Down and to the right on left stick
of transmitter› Only after arming will power go to
servos Buzzer
› Provides auditory feedback (arming error alerts, low battery warning, etc)
› Learn to speak Pixhawk beep (PX4 dialect)
Servo Wires
Be very careful on direction!!!
Order of connection:› 1 – Aileron› 2 – Elevator› 3 – Rudder› 4 – Throttle
Look for indications like this
Lithium Polymer Batteries (LiPo)
3.7V per cell nominally Metrics
› N-cells: 2S means 2 cells (7.4V)› Capacity: 1100mAh› Discharge rate: 25C (27.5A)› Charge rate: 1C (1.1A)
Can catch fire or leak if not properly charged› Never leave a charger unattended
Batteries will brick if you drain too low! What is too low?
› Unloaded: 3.7V minimum› Loaded: 3.3V minimum
Old Slides
Speed Controller
Rated by Max Current and Max Voltage Direct Current Power in, Three-phase Alternating Current out “Opto” vs “BEC”
› BEC can power RC gear, Opto can’t
11
Brushless Outrunner Motor
“Outrunner” - magnets rotate around stator Rated by kV = no load rpm/V
› High kV = fast rpm, low torque› Low kV = low rpm, high torque
Too much power melts windings, burns out motor
12
Power Electronics Setup
13
DC Power
DC Power
3 Phase AC
Carbon Folding Props
More rigid, more efficient, more expensive (vs plastic props) More dangerous – they are spinning knives Spinner cap lets them fold on landing, or if motor braking is on (more efficient
glide)
14
Servos
Drive Motor + Rotation Sensor + PID Control board … in 8-grams
Forcing the control arms by hand wrecks gears
15
www.twf8.ws
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