Advice for BEC / wiring from experienced AP/AV folk

[crayfellow]

Hi guys,

I need BEC/wiring advice. We have a pretty common scenario config-wise, so I am hoping to benefit from your experience in order to avoid unnecessary components.

Power is 6S, and I want to try to power everything from the main source.

5V
* Flight Controller servo rail (backup power)

12V
* FPV flight camera (will use video switcher between this and a GH4)
* FPV OSD and vtx
* LED Lighting

14V+
* 3-axis gimbal + controller (4S equivalent or greater)

I'm an electrical engineer so the technical aspects of this aren't the issue; there are many ways to solve this with various regulators. What I am hoping for is the most elegant solution, one that is informed by your experience.

You AP guys usually have a separate 4S for gimbal, vtx, etc., right? But if I am using the main battery, I might end up with a mess like this:

In frame
* 5V buck for FC (or equivalent via PDB)
* 12V buck for LED (or equivalent via PDB)
* Adjustable higher-current 14+V BEC wired to gimbal (is this necessary, since gimbal/controller could simply run on 6S? the idea was to isolate the gimbal and whatever is connected to it as a safety measure)

On gimbal
* 12V buck for vtx from 14+V BEC source


4 BEC's, seems like the opposite of elegance! I know the 5V and 12V buck could just be one of those PDB's with integrated BEC's, so that would be one simplification.

Also considering the flight camera should be on the frame, would you just wire that down to the vtx source switcher on the gimbal? Or is that nonstandard?

I know these are VERY basic questions with pretty obvious answers, but I'm aiming for elegance and simplicity, and I know you guys have a much better feel for that than I do right now for this application.

Thanks!

 

[stevemaller]

I've used a PDB with integrated BECs and it worked ok until I realized it was spewing EMI and interfering with my UHF receiver. I'd also stick to 12v for your gimbal if it's just a GoPro.

 

[Mactadpole]

I would just do a 5v BEC and a 12V BEC. I believe I read that Jakub (InfinityMR gimbal) said he sees better/equal performance at 12V on the gimbal. That way you have the redundant power to Pixhawk (5V) and you could run these LED's (I use them and like em') at 5V from the rail or rx. Everything else off 12V. It can unfortunately get messy quick.

 

[crayfellow]

thanks for the LED recommendation!

the motivation for looking at >12V for the gimbal was Jakub's recommendation to me via email.
"I suggest using 4s lipo (16V). Motors used in the gimbal can work with 3-4s but in my opinion 4s is better."

But the 5V/12V could come from a little PDB which would power Pixhawk servo rail and LED's.

Some adjustable higher-current BEC could power the gimbal as "4S equivalent" then add a step down to 12V on the gimbal for the vtx (or use a vtx that is happy with 4S and forget about the flight camera)

EDIT: I looked closer at your suggested LED solution; at 5V that simplifies things a lot. 5V to the rail and LED's, then "whatever 12-16V" to the gimbal and a vtx that is happy with 4S. Only thing I'd need 12V for then is an OSD and flight camera, but a tiny Pololu 12V reg can provide that with practically no additional weight.