The first Maker Boat Advanced required real-time underwater video. Obviously, underwater video requires good visibility, so don’t expect to see much in a muddy river, or even in a lake as pictured above. As fans of open source hardware and software and users of ArduPilot-compatible flight controllers, we turned to the Herelink system to meet our real-time video needs. Herelink features a ground unit and an air unit, both of which work with ArduPilot and PX4. The air unit not only provides real-time video, but it also sends MAVlink data to the ground unit, eliminating the need for a telemetry module. The ground unit consists of an Android tablet with two gimbal sticks, six buttons, and a gimbal wheel. The ground unit runs QGroundControl and Solex. As a result, the ground unit eliminates the need for a RC controller and a separate device (laptop, tablet, phone).
Herelink Air Unit Integration
The Herelink air unit is mounted on an aluminum plate in the electronics enclosure on the Maker Boat Advanced. Originally intended for use on aerial drones, the air unit heats up in enclosed spaces. Inside the enclosure, the aluminum plate acts as a heat-sink. Additionally, two cooling fans also help keep the air unit cool. A HDMI ribbon cable sends the video from the GoPro to the Herelink air unit. The SBUS cable connects the Herelink with the autopilot. Two antennas at the top of the enclosure send the video and MAVlink data to the ground unit. The SBUS cable provided connects directly to the Cube. However, the Maker Boat Advanced uses a Pixhawk 4, requiring minor modifications to the SBUS cable. Watch this video if you need help configuring your Herelink.
Powering the Herelink Air Unit
The Herelink documentation states that the air unit requires an input voltage between 6 V and 12 V. However, we found this statement to be somewhat incomplete. In our opinion, the documentation should state that the Herelink air unit only operates reliably with a Mauch 12 V power supply. When powered by other, more affordable, power supplies, the Herelink air unit behaved unreliably. While we found the intermittent connection irritating, it rarely caused major problems. However, this would not be the case if I lost connection with my drone flying at 100 m. The Mauch power supply increases the cost of the Herelink system by over 10%. Please let us know if you have found any other power supplies that work reliably with the Herelink air unit.
Other Considerations
Overall, the Herelink system works well and we are pleased with the results. Not all cameras work with the Herelink system, though. Check here for a list of compatible cameras. The Herelink works with the GoPro Hero5, with limits on both the resolution of the video saved to the SD card, as well as the video streamed to the ground unit. When recording video on the SD card at 2.7K, the GoPro Hero5 Black outputs video at 720p. When increasing the resolution to 4K, the HDMI output resolution decreases to 440p, which the Herelink air unit does not recognize. Thus, we cannot take full advantage of the 4K capabilities of the GoPro Hero5 Black while also viewing real-time video. While not directly related to the Herelink, the GoPro generates a lot of heat when using the HDMI out, which also contributes to overheating issues inside the electronics enclosure. Finally, firmware updates tend to be somewhat disruptive.