My final touch to this project are the remote controlled LED headlights. As most of the other reviewers did, I also decided to use Würth Elektronik’s high power LEDs for my illuminated tricopter. These LEDs are powered using TPS92512 buck converter from Texas Instruments. TPS92512 provides two different ways of dimming and I chose to use PWM as it’s more suitable for my project.
Turing 9X is the remote controller that I use for all my aircrafts. It’s cheap but still provides most of the features that I need - except for being able to receive the telemetry data back from the aircraft. Since I don’t have the real telemetry this project is oriented to adding useful (or just good looking :)) LED indicators to my newest tricopter. Additionally, I wanted to be able to fly at night, at least to near proximity. That's why I planned to add high power headlights. I decided to dedicate one transmitter channel for headlight control. This station has 8 channels of which 4 are used to control the flight (pitch, roll, yaw and throtle), one is used to arm the controller and one is used to switch between flight modes (self-level, free flight etc.).
Receiver demodulates the transmitted signal and then converts the PPM signal into a set of PWM signals that are used to control the servos, ESCs, linear actuators and similar.
Receiver output signals are pulses with varying duration depending on potentiometer/switch positions on the transmitter but duty cycle has a very low range of 5%-10%.
Here, I'm showing the single decoded PWM signal that I use to control the brightness of Würth Elektronik high power LEDs:
So, as TPS92512 expects 0% to 100% duty cycle I had to output the desired PWM depending on receiver pulse duration. For that I added a small function that utilises pulseIn function to my Energia sketch so that I can measure the input pulse duration. Also I had to shift the 5V input signal to 3.3V input for MSP430.
Here you can see both input and output signals (IN: yellow; OUT: blue). This output signal is further connected to TPS92512's PDIM pin to control the LED brightness.
And here how the headlights operate (still not mounted):
Next update with test flight footage will be ready when all parts are mounted and when I get rain-free window of time.