DJI FPV quadcopter build log
Few months ago DJI has released their newest gear for FPV enthusiast – the DJI Digital FPV System. It aims to revolutionize the drone racing industry by providing low-latency HD video transmission. We decided to test it and build a new FPV quadcopter with 3rd party recommended components offered by DJI on their webstore. The idea is to review how easy it is for new FPV pilots to build their first drone with this complete package. And at the same time provide a step by step tutorial how to connect these components.
Before we start with the build log, let´s list the components we have used:
- DJI FPV Fly More Combo (Mode 2)
- TransTEC Laser HD Frame
- 4 x T-Motor HOM KV1750
- T-Motor F55A PRO II + F4 HD Stack
The DJI FPV Fly More Combo includes the DJI FPV Goggles, DJI FPV Air unit (camera is included) and the DJI FPV Remote Controller. Accessories like antennas, power cable, USB-C cable and sleeve are also included. A battery for the remote controller is also included.
The DJI FPV air unit includes the HD digital video transmitter, command & control receiver and integrated DVR in one. It is amazing how DJI integrated everything in such a small box.
Now let´s look at the 3rd party recommended parts for our FPV quadcopter.
The TransTEC HD Laser HD frame was well packed, so nothing gets scratched. The quality of the carbon parts is also great, so hopefully it will stand a lot of crashes. What we really like is how all the screws were packed and marked. Therefore it is super easy to follow the provided assembly manual and use just the next box of screws.
It is no wonder DJI recommends T-Motor motors as these are one of the best on the market. We have tested many of these in the past and quality was always superior. The HOM KV1750 are no exception. You could also use the T-Motor F40 Pro III. These are smaller and lighter, but with high-KV you could go for 4S-battery based quadcopter. Have a look at our F40 Pro III review T-Motor F40 Pro III.
We are also using the recommended T-Motor F55A PRO II + F4 HD Stack. It consist of a F4 flight controller and F55A PRO III 4in1 ESC. Quality of the PCB boards looks great. It is also nice, there is a power cable with XT60 plug, cables to connect to the DJI FPV air unit and a capacitor.
So now let´s start with building the drone. You could also follow the manual for the frame assembly. First we have mounted the 3D-printed antenna holder to the upper part of the frame and inserted the DJI antennas inside. Then mount the DJI FPV air unit to the top plate using the zip ties (included in the frame box).
Note: we have used all 3 zip ties at the beginning, but then realized the 3rd one is covering the USB port. Therefore we removed this. The air unit is still fixed and secured well enough.
In the next step you should use the 3D-printed camera mount and fix the FPV camera to it. Unscrew the camera screws on the side and use these to fix it.
Then assemble the frame (arms and bottom plate) and mount the T-Motor F55A PRO II 4in1 ESC.
Next you can mount the four motors on every arm.
Cut the motor cables to the desired length, so the cables can be nicely soldered to the pads of the T-Motor 4in1 ESC. Fix the motor cables to the arms either with zip ties or tape. In a next step solder all motor cables, the capacitor and the power cable.
Note: pay attention to the polarity of the capacitor. The negative is marked with a grey line and a minus inside it. Make sure you can bent the capacitor till the back of the drone, so you can have enough space to fit the DJI FPV air unit.
The great thing about this combo is, all the soldering is already done. On top of the ESC you put some spacers and fir the F4 flight controller. Fix the flight controller using some of the provided nuts. Then connect the ESC with the flight controller with the supplied cable. In a next step connect the flight controller with the DJI FPV air unit and mount the top frame plate.
This is it! The hardware part is done and you just need to fit your propellers and battery. But before you do that, lets do some software modifications, before the quadcopter is ready to fly.
First lets flash the latest Betaflight firmware to the F4 flight controller. Install the Betaflight Configurator on your computer and connect it to the flight controller with a USB cable. Click on “Update Firmware” and choose the board type (in this case the TMOTORF4).
Then click on “Connect” and go to the “Ports”-tab. Enable MSP on the UART2 port. This will allow the flight controller to provide the voltage information directly on your DJI Goggles screen (OSD).
Enable “Serial RX” on UART5, so you can use the inbuild SBUS receiver in the DJI FPV air unit.
In a next step go to the “Configuration” Tab and setup the protocol for the ESCs to DSHOT600. The F55A PRO II ESC is running BLHeli32 firmware, which supports this protocol and it is much faster than the old OneShot125. In overall it will provide you with a better response and flight experience.
Make sure to also select the Receiver mode and provider as shown on the picture below.
In general these are the basic settings you need to adjust to make sure your drone will fly.
Last but not least, you should make sure the motors are spinning in the right direction. As on every quadcopter two of the propellers should rotate clockwise (CW) and two of them counter clockwise (CCW). The standard, which is defined in Betaflight is shown on the picture below. Motors 1 & 4 are CW and 2 & 3 CCW. You can change the motor direction by either reversing one of the 3 motor cables (hardware change) or by software. Of course the second option is much more convenient as you already have soldered the cables.
With props removed, power on the quad with a battery. Connect your computer to the flight controller (via USB) and open the BLHeliSuite32.exe. Click on “Connect” and the on “Read Setup”. If everything goes fine, you should receive some information about the T-Motor ESC. Then you should select one-by-one every ESC (1-to-4), change the motor direction as desired and “Write”/save the changes.
Note: in our case we needed to change the motor direction on motor 1 & 4 to “reversed”.
In the “Motor”-Tab in BLHeliSuite you can check if the motors are spinning as you wish. Again: no props mounted.
Now your FPV quadcopter is almost ready. Make sure you have activated and registered your DJI FPV Goggles, air unit and remote controller and that you are running the latest official firmware.
After all, mount your propellers, charge your batteries and go out for flying. Enjoy the world of digital HD video!
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