The last incendiary event made me figure out that a new ESC quartet would be required to get the craft off the ground anytime soon. I went and grabbed a bunch of T-Motor Air 20A ESCs, which turned out to be quite the reliable little beasts, and quiet too. The whole cable management business became a bit more messy, in comparison to the integrated ESC I was using. Due to ESC placement on the arms it is no longer possible to pass the motor cables through the carbon fiber tubes. Nonetheless, I am quite happy with the current setup.
BEC and PDB
One issue was that the new ESCs did not have a built-in BEC, so I had to grab a tiny PDB/BEC combo to go together (DALRC Micro PDB):
Below the arrangement of ESCs with the quadcopter PDB and LiPo connectors:
As you can see I’m still using the quad’s PDB, since it allows for shorter leads. I also have the impression that it can handle a bit more current than the 50amps of the DALRC PDB1.
The connection between the battery pads and the BEC turned out to be quite fragile and unstable. This led to the Flight Controller losing power on some occasions. I found out the hard way, when during an indoors flight the aircraft yawed uncontrollably to the right and crashed. Luckily nothing at all was damaged, apart from a broken zip-tie at the motor mount:
Seen from an optimist perspective, the damage kind of shows that the frame did break where it should, and contained the damage from breaking any critical components. Who knows what will happen if it falls from a height of 20m (60 ft) though..
Attaching the FC and Raspberry Pi
I eventually want to attach a Raspberry PI 2 (RPi) to capture video and do computer vision and autonomous flight when my NAVIO2 flight controller arrives. Therefore I started planning where the RPi board would go. The most sensible place seemed to be above the top plate at a distance so that the battery can go underneath it. To make mounting easy I designed customized spacers that could attach to the mounting holes on the RPi but also to the existing arm fixing holes on the top plate of the quadcopter. The following diagram captures the gist of it:
I first tried to 3d print the spacers by positioning them standing (long dimension facing up) as shown in the figure above. Unfortunately the print turned out pretty mangled due to the print head causing wiggling of the upper layers:
Eventually I realized that I had to print them by laying them down on the print bed. The result came out quite good. I didn’t have to use any support at all, because of the small dimension of the holes and overhangs. In use, the standoff looks like this:
And this is what the finalized “beast” looks like:
And, guess what: it flies! And pretty darn well too! Here’s is an animation taken from the video of the maiden flight: