ExpressLRS: Open-source Radio Control Protocol
ExpressLRS, also known as ELRS, is an open-source radio control protocol designed specifically for FPV drones. It offers several notable advantages that make it an appealing choice for FPV enthusiasts. ELRS is available in two main frequency ranges: 915 MHz (868 MHz in some regions) and 2.4 GHz. The 915 MHz version provides longer range but requires larger antennas, while the 2.4 GHz version offers slightly less range but allows for smaller antennas.
ELRS stands out for its long-range performance, with a tested range of at least 40 km (nearly 25 miles). This capability ensures reliable signal transmission even in areas with obstacles such as buildings or trees. Additionally, ELRS boasts low latency, meaning there is minimal delay between control inputs and the drone's response. By adjusting the packet rate, pilots can optimize the balance between range and latency, with a maximum rate of 500 Hz.
One of ELRS's key advantages is its compact size. ELRS receivers are incredibly small and lightweight, weighing only 0.44g for the smallest version. This feature simplifies installation on FPV drones and improves overall flight performance. The antennas for 2.4 GHz ELRS are equally small, and they can be directly mounted on the drone's board without requiring additional wiring.
ELRS offers convenient firmware updates compared to other control links. Users can easily update the firmware via WiFi or USB using flight controller passthrough. This streamlined process enables pilots to keep their ELRS transmitters and receivers up-to-date with the latest features and bug fixes.
Cost-effectiveness is another notable aspect of ELRS. The transmitters and receivers are generally cheaper than many competing options while still delivering exceptional performance. This affordability is particularly advantageous for pilots with multiple drones or those seeking a budget-friendly solution.
When comparing ELRS to other popular control links, such as FrSky and Crossfire, ELRS emerges as a strong contender. It surpasses FrSky in terms of range, obstacle penetration, and firmware update simplicity. ELRS's binding process is also more straightforward. Compared to Crossfire, ELRS offers similar benefits but at a lower cost. Crossfire modules and receivers tend to be pricier, and their antennas are larger due to the 900 MHz protocol. Unless users specifically require Crossfire's smaller receiver size or plan to expand their drone collection significantly, ELRS is recommended as a more cost-effective alternative.
To set up ELRS, you will need a transmitter (radio or module) and a receiver. If you don't have an existing FPV radio, it is advisable to purchase one with ELRS built-in, as this option is more compact and cost-effective. The Jumper T-Pro and Radiomaster Zorro radios with internal ELRS modules are popular choices. However, if you already own a compatible radio, you can opt for an external transmitter module that fits your radio's module bay size. The Happymodel ES24TX modules are commonly recommended.
For receivers, there are different options based on your drone's requirements. Integrated antenna receivers feature soldered antennas directly on the circuit board, offering a compact form factor suitable for small drones. Happymodel EP2 receivers fall into this category. External antenna receivers, on the other hand, have UFL antenna connectors and provide greater range, making them ideal for larger builds. Happymodel EP1 receivers are a popular choice in this category. If your drone lacks a flight controller, PWM receivers like the Mateksys PWM ELRS R24 P are necessary for directly controlling servo motors.
To complete the setup, you will need to solder the receiver to your drone and configure your radio and receiver accordingly. While a written guide is unavailable, there are video resources available that cover the setup process in detail.
Please note
that the information provided is based on my knowledge cutoff in September 2021. For the latest information on ELRS, it is recommended to refer to the ExpressLRS website or relevant sources.