Dodecarotor cox wiring

Pixhawk
1

Hello everyone!

In order to lift my DSLR camera in the air, I decided to design a larger drone and build. So far, I have only experience with smaller fast quadcopter.
I always like to find difficult projects to grow around it, relative to my knowledge.
So the decision fell on a 12 engine machine.

For this I have already done some development work and milled a prototype.

IMG-20190514-WA0010
IMG-20190514-WA00104608×2272 676 KB

I’m currently planning with a Pixhawk 4 as FC. My frame design is designed for 9 inch propellers. In addition T-Motor AIR Gear 350 with 920 KV engines x 12 and 20A ESC’s.
According to my calculations, this should provide enough thrust to lift the weight of the drone + camera long enough, for my needs, in the air.

For me, the following points are currently to be clarified, to which I hope to get constructive answers here. I also attached a plan of the wiring, which is not my greatest strength.

  1. I wonder how 12 motors are powered by the HOLYBRO PM07 PDB for PIXHAWK 4? For this I have an idea (see plan), but I do not know if I think everything right here. Can I realize the power supply of the 12 motors from only 6 connections?

  2. The description of the HOLYBRO PM07 PDB for PIXHAWK 4 says “PCB Current: total 120A outputs (MAX)”. Is this the maximum ampere flow of an output for the engines? Or is it the maximum number for everything together. The latter would be surpassed by the engines at peak load (12 x 20A = 240A).

  3. If the HOLYBRO PM07 PDB for PIXHAWK 4 is not useful in the context of the dodecarotor cox which PDB could I use? What options do I have to fully supply the engines?

  4. The first 6 motors are supplied with a drive signal via the I / 0 PWM line. The other 6 motors are supplied with signals via the FMU PWM line. Unfortunately, I find no explanation for what FMU is the abbreviation, but would like to know.

Dodecaopter%20wireing
Dodecaopter%20wireing3622×2202 1.45 MB

I think I have more questions, but I would be happy to get answers and hints.

greetings
CHO

2

2.3. 120A outputs means all together (not for one output). You can solder one more pdb next to it to have total of 240A. Check how to create double connector for supplying both. Also remember that for example xt60 connector holds up to 60A and xt90 up to 90amp.

3

Hi, one question to point 4:
How did you solved the ESC problem?
In my case the otherr 6 motors get no signal out of the FMU PWM line.

Would be great if you can help me out.

Thanks and regards

4

One more info for this problem:
all top motors 1-6 which are connected via m1-m6 on the PDB are running. But the bottom motors wont spin. these are connected via the FMU PWM out of the PDB.
What can I do that all 12 motors will work?
Thanks a lot to your help guys!!

5

Hi @Mario2410 ,

Can you tell more details about the Firmware version please? Are you using master, v1.9 or a custom or early version?

Can you give the output of
ver git
pwm info
pwm info -d /dev/pwm_output1
dmesg

and best would be the link of a small log file uploaded to http://logs.px4.io .

6

Hi, thanks a lot to your answer:
I use the 1.9.2 firmware.

the outputs and the log file I post you tomorrow when I have acess to the drone.

thanks a lot to you

7

Hi , did you manage to get the signal from the fmu line? With this configuration you use M1-M6 and the other 6 are connect to the fmu. There’s another forum that use M1-M8 and other 4 connect to the fmu.

I am currently on a project of this dodecacopter using pixhawk