Sociopath Community

My dad taught himself electrical engineering. And he did, he was a PhD physicist patent lawyer. He had all kinds of BOOKS. I wish we had saved them when we sold the house. Anyway I always wondered what it would be like to be an engineer and have this level of understanding of the world. Must be pretty sweet.

M4d said: 

My dad taught himself electrical engineering. And he did, he was a PhD physicist patent lawyer. He had all kinds of BOOKS. I wish we had saved them when we sold the house. Anyway I always wondered what it would be like to be an engineer and have this level of understanding of the world. Must be pretty sweet.

 That's cool your dad sounds like a smart guy. You should make a thread about your dad. I'd love to read it.

Being new to thing remote control (RC) flying thing I first had to understand how all the pieces fit together.

Here is a picture of the simplest RC system.

The hand held radio transmitter talks to the radio receiver in the RC airplane. ExpressLRS is the software used to manage and talk. The airplane receiver gets commands and instructions from the hand held transmitter on the ground.

The airplane radio receiver then passes these commands, such as throttle up, throttle down, aileron position, elevator position and rudder position on to the control servo motors and the motor electronic speed control (ESC).

Each servo motor or ESC is on one channel of the receiver.

The airplane receiver is just a slave or middle man to the hand held transmitter on the ground.

More complex systems have a flight control computer with telemetry, GPS and other options. More to come on the more complex systems.

Some tech. on servo motors.

Aileron position, elevator position and rudder position are controlled by servo motors. Servo motors can precisely control the positioning of these airplane controls. Servomotor are controlled by carefully-timed pulses from the receiver.

The timed pulses is called pulse width modulation.

The servo has three wires: power, ground, plus a third wire to carry the command pulses.

"Internally, the mechanism of a servo motor uses a potentiometer attached to the rotating shaft to sense the position. It measures the width of the incoming pulse and applies current to the motor to turn the shaft, until the potentiometer indicates that the position corresponds to the incoming pulse width. This is a form of feedback control. The motor has received the desired position from the pulse width, and the actual shaft position is fed back to the circuit via the potentiometer. It compares the desired value to the actual value and drives the motor in the direction that causes actual to match desired."

The servomotors are connected to the airplane control surfaces by connecting rods. This allows the aileron position, elevator position and rudder position to be controlled remotely via the radio transmitter.

Now, about the electronic speed controller (ESC) for the motor.

Similar to the servo control the ESC controls the speed of the motor with a pulse width modulated signal from the receiver.

"When the user adjusts the throttle on their remote control, the receiver sends a signal to the ESC. The ESC then adjusts the PWM signal sent to the motor, which in turn adjusts the speed of the motor. The higher the PWM signal, the more power is sent to the motor, and the faster it spins."

So the ESC is like a middle man taking commands from the airplane receiver and then passing the commands along to the motor. This picture shows two ESC's and two motors.

Now that the basics are complete, we can move on to more advanced topics.

The fight controller.

The simplest planes have a receiver only passing the PWM signal directly to the servo's and the ESC, more complex planes have an advanced flight controller computer that sits between the airplane radio receiver and the servos and ESC.

This flight controller allows many more advance features to be implemented such as telemetry on the airplanes systems, video camera enhancements, autonomous flight modes and GPS navigation.

This is where ExpressLRS comes in. An ExpressLRS firmware is loaded into the flight controller for these advanced features.

Here is a picture of a typical system with a flight controller.

You can see from the image that many devices are wired to the flight controller like, the servos for controlling the airplane, the ESC motor controllers, a USB C computer interface and buzzer, a GPS, a CRSF compatible radio receiver (more on this later), I2C devices like a speed sensor, cameras and a camera video transmitter.

"ExpressLRS is an open source Radio Link for Radio Control applications. Designed to be the best FPV Racing link, it is based on the fantastic Semtech SX127x/SX1280 LoRa hardware combined with an Espressif or STM32 Processor. Using LoRa modulation as well as reduced packet size it achieves best in class range and latency. It achieves this using a highly optimized over-the-air packet structure, giving simultaneous range and latency advantages. It supports both 900 MHz and 2.4 GHz links, each with their own benefits. 900 MHz supports a maximum of 200 Hz packet rate, with higher penetration. 2.4 GHz supports a blistering fast 1000 Hz on EdgeTX. With hundreds of different hardware targets from a wide range of hardware manufacturers, the choice of hardware is constantly growing, with different hardware suited to different requirements."

Here is an image showing the ExpressLRS needed software.