I decided to get into the FPV Racing Drone scene and found this unit available in an almost ready to fly version for $140.
Almost ready to fly means that I need to add my own transmitter and receiver. Because it’s FPV, it also means that I need my own video receiver and display.
I have an FrSky Taranis transmitter, several compatible receivers, and a set of Fatshark Attitude V2 goggles, so when the model arrived, I expected all I would need to do was charge the battery and it was ready to fly.
It turned out it was slightly more complicated, but the past three years of playing with drones meant that it wasn’t too involved.
First I found a useful wiki page dedicated to the racer, with plenty of information. It allowed me to understand that I’d got version 5 of the racer, with the difference from version 4 being that they’d removed a safety tray that kept the battery from crushing the flight controller.
I figured out that to use S.Bus to communicate between my receiver and the flight controller, I’d need to download software to my PC, connect the PC to the flight controller with a USB cable, and configure it’s inputs. The instructions I found all referred to OpenPilot. OpenPilot is an open source project that is now defunct, including the domain name itself not going anywhere. The replacement project that is functionally similar, is LibrePilot. I believe that http://opwiki.readthedocs.io/en/latest/user_manual/index.html is the old documentation from the OpenPilot project, while the LibrePilot home page has links to all of the new project.
After downloading LibrePilot and installing the software on my PC, I couldn’t change the settings on the firmware that had shipped on my drone without upgrading to new firmware and resetting all of the configuration. After some hesitation, I allowed it to upgrade, then followed the wizard to configure the new firmware. I was impressed at the ease of setup, and later when I flew the device, it proved that the defaults worked nicely out of the box.
The original firmware had a rose icon, while the new firmware shows a warning icon. That could mean something important, but I never found any mention and the system seems to be working correctly. You can see that the drone shipped with a firmware dated 2015-03-12 and the new version is dated 2015-10-21.
Connecting the receiver to the flight controller using the S.Bus connection required using the MainPort connection on the flight controller. An appropriate cable shipped with the device that included 4 wires, colored black, red, green, and yellow. For S.Bus operation, the green wire is not used. I removed it from the flight controller side of the cable. When connecting to the receiver S.Bus, Black = (-) Red = (+) Yellow = (Signal).
My goggles only support 8 channels. The drone video transmitter supports 32. Finding a match required a bit of reading, and then deciding on what was least likely to cause conflicts with other people near the field I regularly fly at. I chose D7 on my transmitter and CH6 on my goggles, which worked out to 5840MHz. The newer version of my goggles supports 32 channels. (8 channels, on each of 4 bands.)
I found that http://www.rcgroups.com/forums/showthread.php?t=2266883 has a very nice explanation of the frequency bands used for FPV including details of how they overlap and recommendations for which frequencies to chose for the least interference between racers. It includes a google docs spreadsheet that’s been color coded to have the frequencies sorted in ascending order and make the bands more visible.
I got the video transmitter and receiver in sync by selecting the channel on my goggles, then cycling through all of the possible channels on the transmitter until I got the clearest video picture. My goggles auto select NTSC or PAL depending on the signal they receive. A friend using a full sized monitor wasn’t as lucky. That’s how I figured that the Eachine Racer 250 ships with a PAL camera.
The Eachine Racer 250 has a pair of bright white LEDs on the front, one on either side of the camera, and a LED lightbar on the back. The LED light bar on the back can be cycled through a series of colors by sliding a power switch located on the left side of the main board that turns all the LEDs off and on. There is also a two pin cable connector that can be plugged in to a receiver PWM output allowing remote light control. To use remote light control, the local switch on the drone must be in the OFF position. I’ll write more about this in a separate post.
After going through the LibrePilot setup wizard and putting the appropriate propellers on each motor, the racer flew completely as expected. It’s very responsive, and also very resilient to the basic crashes I’ve had so far. The biggest learning experience for me has been to add throttle when I think I’m going to crash on the ground. With my larger drones, I’ve wanted to stop and recover the drone when it hits the ground. With this drone, it is much more likely to bounce and be able to recover itself if I can get it off the ground. I recommend this drone as a good entry into the FPV racing drone scene. I’m sure that there are plenty of drones that are more resilient or responsive, but there’s also plenty more that can be spent than I did on this.