AA241x
H A RDWA RE
AND
S OFTWA RE O V E RV I E W
Spring 2015
Adrien Perkins
Pixhawk
 168 MHz Cortex M4F CPU
 2 MB Flash
 4 GB SD card – many many hours of logging
Wireless Telemetry (3DR Radio)
 915 MHz, 100 mW
 Unique “NetID” for each set
 Mavlink Protocol
DF13 6-Pin
USB Micro
USB
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 6pin
GPS
DF13 4pin
MAG
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
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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
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Power Electronics Setup
DC Power
DC Power
3 Phase AC
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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)
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Servos
 Drive Motor
+ Rotation Sensor
+ PID Control board
… in 8-grams
 Forcing the control arms
by hand wrecks gears
www.twf8.ws
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