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

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Introduction

If you're a hobby RC pilot or maker in the UK looking to upgrade your fixed wing aircraft's radio system, ExpressLRS (ELRS) is a fantastic choice. It's a long-range, low-latency open-source RC link that offers excellent performance and reliability. In this guide, we'll walk you through setting up ExpressLRS on a fixed wing plane using PWM outputs, perfect for those using traditional receivers without built-in serial outputs.

What You’ll Need

Before we start, make sure you have the following components:

  • An ExpressLRS compatible receiver (e.g., a 2.4GHz or 900MHz ELRS RX module)
  • A flight controller with PWM input capability (or a simple PWM servo tester board)
  • A compatible transmitter module or ExpressLRS radio transmitter
  • Battery and wiring appropriate for your setup
  • Access to the ExpressLRS Configurator software on your PC

Step 1: Flash the Receiver Firmware

First, you need to flash the appropriate ExpressLRS firmware on your receiver. Download and install the ExpressLRS Configurator from the official GitHub or website. Connect your receiver to the PC via USB or an appropriate programmer, then select the right hardware target and desired radio frequency (2.4GHz or 900MHz). Flash the firmware following the on-screen instructions.

Step 2: Bind the Receiver to Your Transmitter

Once flashed, bind the receiver to your ExpressLRS transmitter module. Usually, this involves putting your transmitter into bind mode and powering up the receiver while holding a bind button or shorting pads, depending on the RX model. Wait for the LEDs on the receiver and transmitter to indicate successful binding.

Step 3: Connecting the Receiver to Your Flight Controller

Since your flight controller (FC) uses PWM inputs, you’ll connect each channel output from the receiver to the corresponding PWM input pin on the FC. Unlike serial protocols like CRSF, PWM sends individual signals for each channel on separate wires.

Typically, an ExpressLRS PWM receiver has multiple servo-style outputs, each providing one channel's PWM signal. Connect these channels as follows:

  • Throttle (THR) to FC's throttle input
  • Aileron (AIL) to FC's aileron input
  • Elevator (ELE) to FC's elevator input
  • Rudder (RUD) to FC's rudder input
  • Additional channels (flaps, gear) as needed

Make sure to connect the receiver's ground and 5V power lines to the FC or power source as well for stable operation.

Step 4: Configure Your Flight Controller

In your FC's configurator software (such as Betaflight, INAV, or ArduPilot), set the input protocol to PWM for your receiver inputs. Calibrate the sticks and channels to ensure correct responses. You may need to reverse channels or adjust endpoints depending on your setup.

Step 5: Final Checks and Testing

Before flying, do some bench tests. Power up the system and move your transmitter sticks to verify the servo outputs and FC inputs respond correctly. Check for any signal loss or noise, and ensure the receiver LED indicates a strong link.

Tips for a Smooth Setup

  • Use quality shielded servo cables to reduce interference.
  • Keep your receiver antenna clear of metal parts for best range.
  • Double-check power connections to avoid brownouts.
  • Always test range and control response in a safe area before flying.

Conclusion

Setting up ExpressLRS with PWM outputs on a fixed wing is straightforward once you know the steps. With ELRS's great range and low latency, your flying experience will improve significantly. Happy flying and tinkering!

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