How to Set Up ExpressLRS on a Fixed Wing with PWM Outputs

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Introduction

ExpressLRS (ELRS) is a popular, open-source radio control system known for its low latency, long range, and affordable hardware. Setting it up on a fixed-wing aircraft with PWM outputs is a fantastic way to boost your flying experience, especially if you're a DIY enthusiast or hobby pilot in the UK. This guide will walk you through the essentials to get your fixed wing flying smoothly with ExpressLRS.

What You’ll Need

Before diving in, make sure you have the following:

  • A compatible ExpressLRS transmitter module (e.g., a 2.4GHz module)
  • An ExpressLRS receiver with PWM output support
  • A fixed-wing aircraft with a flight controller or direct servo connections
  • A computer to flash the firmware (Windows, Mac, or Linux)
  • USB cable for flashing
  • Basic soldering tools (optional, depending on hardware)
  • ExpressLRS Configurator software (available on GitHub)

Step 1: Flash ExpressLRS Firmware

First, you need to flash the ELRS firmware onto both your transmitter module and receiver. This ensures they can communicate properly.

  1. Download and install the ExpressLRS Configurator from the official GitHub repository.
  2. Connect your transmitter module to your computer via USB (or through your radio if it supports direct flashing).
  3. Select the correct target hardware and desired settings (e.g., 2.4GHz, power output, and packet rate).
  4. Build and flash the firmware to the transmitter module.
  5. Repeat the process for the receiver by connecting it to your computer via a USB-to-serial adapter or appropriate interface.

Step 2: Wiring the Receiver to Your Fixed Wing

ExpressLRS receivers typically provide PWM outputs on individual pins, which can be connected directly to servos or to a flight controller that accepts PWM inputs.

  • Identify the PWM output pins on your ELRS receiver. Usually, these are labelled as CH1, CH2, CH3, etc.
  • Connect the PWM signal wires from the receiver to the corresponding servo inputs on your flight controller or directly to the servos.
  • Remember to connect power (5V) and ground wires correctly to avoid damage.
  • If using a flight controller, ensure it’s configured to accept PWM inputs on the ports you’re using.

Step 3: Binding the Receiver and Transmitter

Binding links your transmitter module and receiver so they communicate securely.

  1. Power on your receiver in bind mode (usually by holding a button while powering up or by connecting a bind plug).
  2. On your transmitter module, enter bind mode through the ExpressLRS Configurator or by using the dedicated button.
  3. Wait for the binding process to complete, indicated by LED changes on both devices.
  4. Power cycle your receiver and transmitter to exit bind mode.

Step 4: Testing and Calibration

Once bound, test each channel to ensure the PWM outputs respond correctly to stick movements.

  • Move the sticks on your transmitter and watch the servo or flight controller respond.
  • If using a flight controller, configure your radio settings (e.g., channel mapping, endpoints) in your flight controller software (Betaflight, iNav, etc.).
  • Calibrate servos or control surfaces to make sure movements are smooth and within expected ranges.

Tips for UK Hobbyists

  • Check local regulations for 2.4GHz usage and maximum power output.
  • Use a good quality antenna and position it correctly on your aircraft for best range and signal stability.
  • Always test your setup on the ground before flying to avoid surprises.

Conclusion

Setting up ExpressLRS on a fixed wing with PWM outputs is straightforward and rewarding. With low latency and robust signal quality, ELRS can significantly improve your flying experience. By following this guide, you’ll have a reliable, DIY-friendly RC link ready to take to the skies. Happy flying!

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