I’ve made some pretty major upgrades, additions, and modifications to my quadcopter recently, so I thought now would be a good time to do another post. The base for this quad is still the same one I’ve been using for nearly a year now, which was the subject of the post about upgrading from KK2.0 to APM2.5. Some of the parts are the same but it’s hardly recognizable as the same machine. First, here are the things that haven’t changed:
- Frame – I’m still using the same DJI Flamewheel F450 frame that I reviewed in this post. Never had any trouble with it aside from replacing one broken arm.
- Motors – The same Turnigy D2830-11 1000kv brushless motors from my first quadcopter build and the Lunchbox Copter are still going strong.
- ESC – Same Turnigy Plush 25A speed controllers
- Props – The 9×4.7 and 9×4.7R Slow Fly electric props are still my propeller of choice for this quad
Now on to the good stuff. The biggest change on the quad is the autopilot. I upgraded to the 3DR Pixhawk with power module and 3DR external compass/magnetometer. One of the nice features of the Pixhawk is the buzzer which gives audible alerts for things like motors arming and low battery. There’s also an integrated safety button so you can power up the quad but can’t arm it until the safety button is pressed. The button and buzzer combo make for a much safer flying experience and lower the chances of something going wrong. The Pixhawk also has much more processing power than the APM, so eventually the code can be extended and additional sensors and functionality can be implemented.
I put the Pixhawk in the center of the frame where I had the APM and put the GPS/mag module on the front of the frame on a GPS stand like this to keep it up above the rest of the electronics and power cables which can cause interference. The power module went on the back of the frame.
The other major addition to the quadcopter is the brushless gimbal. I’m using this 2-axis gimbal and this control board from RCTimer. Designed to carry a GoPro, this gimbal actually performs pretty well after a little tuning. I found the tips and advice in this RCGroups thread extremely helpful when setting it up and tuning it. If you are going to use this gimbal, it is a good idea to have a dremel, file, and assortment of small metric screws, because as many people have also reported, I did not get all the correct screws from RCTimer and there are likely to be some minor adjustments you need to make to some of the pieces or screw holes to get it to fit together and rotate smoothly.
To accomodate the gimbal, which I attached to the front extension of the bottom frame plate using a couple of 4mm metal bolts, I had to get some extended legs because the F450 frame sits so low to the ground. Thankfully you can get cheap extended legs that attach easily using the existing mounting holes on the frame. I use this landing gear from RCTimer. I wanted to add about an extra inch of clearance to keep the gimbal off the ground so I did some cutting, drilling, and zip tying and attached pieces of some other plastic parts I had laying around to the ends of each of the four legs.
Once I got the gimbal tuned and working well, I wanted to add the ability to adjust the tilt using my radio transmitter. To accomplish this I ran a wire from the RC9 output on the Pixhawk to the receiver input pins on the gimbal control board. After adjusting a few settings in Mission Planner it worked like a charm.
Speaking of the radio transmitter, I decided to upgrade from the Turnigy 9x. The Pixhawk is what’s called a PPM-input autopilot, which means “it gets RC input from a single cable to the receiver, either via the PPM port, the Futaba S.BUS port, or the special satellite receiver port for Spektrum gear.” I went with the Spektrum DX7s transmitter and the Spektrum 9645 DSMX Remote Receiver, which plugs directly into the Pixhawk without the need for an encoder board.
The last modification I made is to add some LEDs to the bottoms of the motor mounts. I put white LEDs on the white arms and red LEDs on the red arms, to help with orientation, especially when flying in the evening. I had some red and white waterproof LED strips from HobbyKing lying around from an octocopter project so I cut off a small strip of 3 LEDs for each arm of the quad and ran some small power wires along the arms and soldered them onto the PDB where the ESC power wires attach.
For batteries, I’m still using 3S 3000 or 3200mAh on top for the main flight battery, and I strap a smaller 3S 1800mAh on the bottom to separately power the gimbal. Getting around 5 minute flight times, which could be improved by upping the battery to a 5000mAh.
Here’s a closeup:
I took the quad out to a racetrack and got some sweet GoPro footage of some fast cars in action. Here’s a pic of the quad in flight: