Friday, July 12, 2013

Review: Hummer Brushless Gimbal for DJI Phantom and GoPro Hero 3

Figure 1: Hummer brushless gimbal, straight out of the box before any modifications

The Hummer Brushless Gimbal is a 2-axis direct-drive brushless motor camera gimbal designed specifically for use with the DJI Phantom quadcopter and the GoPro Hero 3. It comes with everything you need, fully assembled and configured, right out of the box. No configuration, assembly, soldering, or balancing is required, making it a true plug-and-play system. However, in my testing I found a couple modifications that can be done to make it better.


Material: 2mm carbon fiber plate
Weight: 146 grams (includes cables)
Firmware: Alexmos 1.3B1 (preinstalled)
Power: 3S LiPo (JST connector preinstalled)
Current: 0.3 to 0.4 Amps
Tilt Range: 180 degrees
Roll Range: 60 degrees

Installation and Connection

The top plate of the Hummer gimbal assembly has two holes that precisely match the positions of the mount holes under the DJI Phantom. Two screws are included to secure the top plate to these mount holes. The rest of the gimbal assembly is suspended from this top plate via O-rings. Each O-ring has a chunk of yellow foam inserted to provide vibration damping and stabilization. The foam itself is worthless because it's too soft and easily compressible, but I rectified this by replacing it with small squares of 1/2-inch thick DuBro foam. 

Figure 2: The Hummer gimbal comes with these useful connector cables pre-soldered to the main board
Fortunately the Hummer gimbal comes with connector cables pre-soldered, instead of providing header pins to connect them yourself. There is so little extra space under the DJI Phantom body that having header pins sticking up out of the control board would be inadvisable due to space constraints.

These cables include white signal wires to adjust pitch and roll. Configure your transmitter to apply greater or less than 1500 PWM to move roll and pitch, and exactly 1500 PWM to lock in the adjusted roll or pitch setting. I only connected the pitch control wires, since I have no need for roll to be anything other than level with the horizon.

Also very convenient is that the Gimbal includes a built-in video-out/power cable for your GoPro Hero 3. The end with the servo connector plugs into most video transmitters' video out, GND, and +5V pins (if your video tx doesn't supply a +5V out sufficient to power a GoPro, or you want to power your GoPro from its own battery, then you can leave this red wire disconnected). See Figure 2.

Figure 3: Nuts added to either side of bearing to prevent it from slipping out

Note that the bearing opposite the tilt motor is not well installed, and tends to pop out of the hole in the carbon fiber plate that seats it. I resolved this by simply adding a nut on either side of the bearing to keep it in place (fortunately the shaft came already threaded for this purpose). See Figure 3.

Testing the Hummer Brushless Gimbal

Figure 4 below shows the Hummer brushless gimbal and GoPro 3 installed on the DJI Phantom. The GoPro fits into the gimbal by friction alone, so it's very easy to remove when you want to--no need to muck with unreliable velcro straps.

It's also very easy to remove the mount when you don't want to use it. Just unhook the O-rings from the mount and leave the top plate and O-rings attached to the copter, or remove the two screws holding the top plate on as well, if you wish.

In my tests I found the Hummer to be an excellent gimbal, perfectly suited for the Phantom and GoPro 3. The only major issues I had were the low-quality foam that came supplied with it, and the problem of the bearing popping out, both of which were easy fixes.

Figure 4: Hummer brushless gimbal installed on DJI Phantom airframe
My first use of the Hummer Gimbal was on my ArduPhantom, testing my SplineNav code:

But for a more extreme test in high winds, I made this video, flying the ArduPhantom in 25 km/h winds with very bouncy turbulence down among the treetops. Watch how the trees flail around, especially near the end of the video as the oncoming typhoon gains strength. The aircraft was bouncing around severely, but the Hummer gimbal reduced the movement significantly, although not completely, considering it can only stabilize pitch and roll, not yaw or linear motions:

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