AA241x Spring 2015 Adrien Perkins H ARDWARE AND S OFTWARE O VERVIEW

 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 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 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 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