September 12, 2017

FPV150 revisited

Today I finally spent some time one the FPV150 I built a year and half ago. I was quite satisfied with the machine except for a few issues. First off, it sometimes does strange things while flying, like tilting and pitched. Second, the flight controller is mounted so badly it must be unscrewed to connect the USB wire. And the flight controller; well it's a CC3D.

I have noticed the stream of all-in-one flight controllers integrating more and more functions in one single unit. First off was the PDB, but then voltage sensors, current sensors and OSD chips have been added. Even video transmitter on the most recent ones. I got myself the "HGLRC" F3 V3.1. It is essentially some form of Seriously Pro racing F3 clone. I regret not getting the version with video transmitter while I was at it.

I started with a weigh-in. Always interesting to see how this effects the weight. I'll be ripping out three parts and putting only one back in to replace them.


Ok. Now let's open her up. I remember it was quite hard to get it together with all the wiring and boards crammed into the the body.


I remembered correctly. Inside I found a CC3D board in a small form factor, a "super simple" OSD board, a orangerx receiver of some kind. I had used the PDB that came with the Diatone frame. And a noname video transmitter. So I ripped out everything but the transmitter that I left on the top plate of the frame.


Left was only the motors and the OSD. After this image was taken, I also de soldered the ESC leads and removed the camera "assembly". Then I started putting her back together again. First off soldering the ESCs to the PDB. Well, the PDB means the flight controller in this case.


I picked this particular board because i got the feeling that they had made many iterations and improvements on it. This can always be fake and a noname product from China can be utter crap no matter what facade they try to put up. But I think they've gotten quite far with this one. It is made to be fitted in a racing multirotor craft of course, and as such has the wire leads for the ESC just like the motor layout in clean/beta flight. Only this detail is fantastic alone compared to board from the history of FPV racing. It also has easily accessible solder pads for the receiver, instead of trying to put together one of those microscopic connectors for the receiver.


And this is what it looks like with almost everything wired up. Neat compared to what it looked like a few hours back.

I put everything together. No big deal. I kept the buzzer connected to a PWM output on the receiver. This is simply because I've had very little luck with buzzers connected to the flight controller so far. So I'd rather not. After everything was assembled I weighed it again. I was only 2 grams down. Well, I checked the weight of the parts I removed and the weight of the flight controller and it was essentially the same. The 2 grams is probably due to a bit less wiring. Maybe the capacitor that I forgot to solder back on.

After putting everything together I realized there is a big hole on the bottom of the quad, exposing the flight controller. The PDB covered this hole before. 


So I printed a piece of plastic to cover it up.


Setting up betaflight took me probably 2 hours in total. Almost as much time as the build itself. It is simply because I ran into a few issues with the setup and the work went completely without hickups for once.
I had a big problem with the board not arming as expected and I had to do a few things to get it sorted.
  • Upgrading the firmware. Because at some point betaflight stopped displaying receiver signals in the GUI. Maybe betaflight updated in the background and I needed to put in a new firmware. I don't know why.
  • Lower the refresh rates in the PID. The board reported 7% load but the LED indicated overload. I have no idea why.
  • Set the min_check manually. When upgrading the firmware I used the "diff" command as recommended to store my setup. For some reason diff exported a min_check = 0. I don't really know why.
Feels like flight controller setup routine. I have no idea why, but I had to fix 3 things and now it works. I just hope it stays that way!

Footnote 1: I weighed my JJPRO 130 as well to see the difference. At 195 grams I understand why it barely flies. It is too heavy for flying with only 3-inch propellers. It was a big disappointment as it was a drop-in replacement for the FPV150 that I never took the time to fix.

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