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

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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

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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)

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Servos

Drive Motor + Rotation Sensor + PID Control board … in 8-grams

Forcing the control arms by hand wrecks gears

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