 |
| The Tarot T-2D V2 Gimbal |
The Tarot T-2D V2 gimbal that came with the hexacopter had been sitting idle for a while because it can't be used without a GoPro 3 or 4 to mount in it as a counterweight at the least. I had been concerned about the status of the gimbal because Sebastian had claimed that it needed to be tweaked, and at one point had mentioned that it might need a new board, so it had been prompting me to try to acquire a GoPro quickly so I could test the gimbal.
So I sold off all my old quads and their associated spare parts to put together enough cash to get the camera. With my PayPal account loaded up for a shopping spree, I was just not having any luck at all finding a suitable camera used on the web, which would have been my "go to" method of getting the camera. In retrospect, this was a fortunate happenstance for a couple of reasons. It didn't occur to me at first that I would have my money tied up in a camera that I really couldn't use if the gimbal turned out to be unusable! I'd have to save up to either repair or replace it before the GoPro would really be of use to me, and that money could (and will) be put to a more immediately useful purpose, which is to add FPV capability to my FW550. Actually, the test flight for the gimbal proved to me that FPV capability is absolutely required to make the copter truly useful as an aerial imaging platform. Those parts were readily available, and are on their way to me at the time of this writing. I'll post all about the installation and testing when they all get here.
But for now - back to the gimbal...
 |
| GoPro mounted up - not too tightly! |
I was able to borrow a GpPro 3+ Black edition from Bill, the media minister at my church (thank you SO much, Bill!), and I set about mounting the camera to the gimbal. WARNING: This camera is a very tight fit for the gimbal. If you have one of these gimbals, be certain to only tighten up the blue retainer just enough to hold the camera in the mounting. I'm pretty confident that tightening it down all the way would damage your camera!
I re-installed the gimbal on the front of the hex.
Instead of powering it off the flight battery, as Sebastian had done, I decided to try to use a smaller 800 mAh 12.6 volt (3S) battery that Sebastian had also sent along to separately power the gimbal. This is because I am using a 5000mAh 4S (16+ volts when fully charged) LiPo as a flight battery. In researching this gimbal I discovered that while the manufacturer says that you can power it from a 4S battery, the power regulators on the board get very hot and this can lead to failure of the board.
 |
| 3300 mAH Counterweight! |
Unfortunately, the 800 mAh battery did not weigh nearly enough to counterbalance the gimbal and camera when installed on the mounting plate at the rear of the hex. I decided instead to use one of the two 3300mAh LiPos that Sebastian had sent to provide power as it balanced the gimbal well and provides a suitable voltage. The downside to this was that it made the airframe much heavier. I wasn't a big fan of this approach, but at the time it seemed to be okay for testing purposes. In fact it flew well during the tests where I used it in this configuration. It just felt really "heavy", as it would reduce altitude alarmingly quickly when bringing down the throttle and seemed to need a little more throttle to hover than normal. I really shouldn't need this much weight to get things balanced.
A short side note: while shopping for the FPV parts I came across a really nifty solution to the whole balance issue - a camera positioning kit from a company called HeliPal. Essentially, it's a couple of 660mm carbon fiber rods and the associated hardware required to mount the gimbal way out at the front of the hex in front of the motors, and the flight battery at the rear at whatever point it needs to be to balance the center of gravity front to rear. The camera mounting rails I currently have installed on the hex do much the same job, but they are much shorter than the ones on the camera positioning kit. If I end up seeing the front props in my video I think I'm going to see if I can source the 660mm CF rods and an extra battery tray to duplicate this great idea with my current gear.
 |
| Baby battery up front... |
 |
| Flight battery to the rear. |
Back to the gimbal...
Later (after my initial test flights) I was able to rectify my weight issue. I discovered that if I were to mount the 800 mAh battery on top of the gimbal and mount the flight battery to the rear of the airframe I (just barely) got a good balance front to rear and a nice reduction in weight.
I'm guessing that Sebastian may have had this in mind when he sent the smaller battery along in the first place. The more I work on this airframe the more I appreciate all the goodies that he sent along. Thanks Sebastian!
So, now I have the gimbal and camera mounted and balanced. Time to check it out and see how (or if) it works.
Although the official documentation leaves a lot to be desired (and a lot unsaid) there is absolutely no shortage of end user instructions for setting up this gimbal, and I have scoured the web to read as much of it as I could. Unfortunately it's a mixed bag as far as reviews of this gimbal are concerned, so fearing the worst and hoping for the best, I plugged in the power.
Good! It initialized right away and brought itself to level - well, most of the way to level - the roll motor doesn't quite put the camera truly level. I'm not too worried, I've read of several fixes for this problem and I'm certain that it can be corrected. I picked the airframe up and moved it around to see how the gimbal reacted. Again - good! the gimbal was able to keep the camera in place even in some reasonably extreme positions, just like it's supposed to. No "freak outs". No resets. No power issues. Touching the powered up and running gimbal I could fel no motor vibration at all, which means that it's pretty well tuned up already. With this out of the way I am confident that any problems I would run into from here on would be solvable by adjustments in the software parameters. The gimbal lives!
Next job is getting the gimbal programming software loaded on my laptop and getting it connected to the gimbal controller. Please note that the manual and the software are compressed using the .rar compression method, so you'll need to install a program like the very good (and free) 7-Zip program in order to extract the files from the archive. I'm fairly PC competent, so the driver installation went off without a hitch and the software connected to the USB programming "dongle" with no problems, although many folks report having trouble with this step.
The software itself doesn't come with an "installer", you can run it just by double clicking the .exe file.
As I said earlier, there's no shortage of end user tutorials for programming the gimbal controller, so I'm not going to go through a step by step how-to for this article. I will say that the software is not very intuitive, and has a few "gotchas" - things you will need to know in order to ensure that things work without a hitch. Do what I did - use your friend Google and read as many of these end user instructions as you can. At this point I think that most of the "gotchas" have been documented multiple times, but they aren't all necessarily in the one place.
First I checked the current firmware version running on the gimbal. If you don't have a current version of the firmware installed all sorts of unfriendly things can happen. Fortunately, Sebastian had the latest version (1.5) installed, so we're good there. Given how well behaved the gimbal has been so far I suspected that this would be the case.
Fixing the not quite level roll position ultimately turned out to be a simple matter of running the calibration routine in the gimbal controller software. One time through and it's done - the roll motor puts the camera exactly where we want it now. I've read where this might take a few passes to get it right.
Next I wired up the pitch control to the Aux3 channel on my receiver, and set the range of travel that would be allowed when turning the knob. Sebastian had not given the knob very much travel when he initially set this up, so I canged it to be able to point straight down as the down limit and about 45° as the upper limit. After the test I believe that I'm going to either change the upper limit to have the camera looking straight forward, or mix in a switch that allows me to either work off the knob to position the camera or flip the switch to make it point straight forward, as it can be a little hard to know when the camera is in the forward position.
Sebastian had originally cabled the Aux3 channel through the Naza flight controller for gimbal control. I've read that this is not only truly unecessary (since the gimbal already has its own controller), but it can also cause problems (for the same reason). At any rate, the tilt function is working perfectly now, and I'm quite happy.
Time for a test flight! Here is the raw video from the GoPro:
{mp4}GOPR0014_trim{/mp4}
It looks pretty good, although I'm not sure if the slight back and forth motion I sometime see is a problem or me testing by shaking the airframe in flight. I'll have to test again without trying any funny business to verify this and find a cure if it is a problem. Even so, I'm quite pleased with the performance so far.
I also can see by this video where having FPV (first person viewpoint) is a must. I had tried to fly over the small telescope dome and look down inside, but it's nearly impossible to know when you are actually over it from the pilot's position on the ground. With FPV, this would have been simple to do. Can't wait until all the gear gets here!
Now I need that GoPro! I think that I might be getting one for my birthday....
Charlie