I am attempting to mount a Rasberry Pi 3 onto my F450 based frame Quadcopter, using a Pixhawk as the flight controller.
Ive read on some forum an approach to powering the Pi on a such a build, would be to directly wire a 5V UBEC to the main LiPo.
What would be the difference If i instead wired the UBEC to the power distribution board of the F450 frame? The difference being it would be wired in after the power has passed thru the Pixhawk's power module.
This would be a easier, but i'm unsure if it introduces other issues.
Any advice?
Replies
Yes
So would this diagram be accurate?
OK I see the confusion,
You are actually right, but that big red wire isn't really "from" the Power distribution board, it is simply a resistive shunt so the total amperage (current) can be "read". as well as the battery supply "to" the power module.
Normally when you say "from" a power module or power supply or UBEC you are referring to the modified power the power supply itself is producing.
In this case you are perfectly OK using the PDB to supply power to the UBEC and that is actually the best place to do so as it allows the Power module - Pixhawk to see the total current being consumed including that of the UBEC / Pi3.
Also you are very much right in using a separate UBEC to supply power for the PI as the power module does not have any spare power to do this.
If your ESC's have built in BECs it it possible that one of them might be sufficient to power the Pi, but you would have to check that the power is sufficient.
Also, you cannot increase the available power by wiring ESC BECs in parallel so the power from one ESC BEC would need to be sufficient.
Im a bit confused,
According to this:
http://ardupilot.org/copter/docs/common-3dr-power-module.html
The battery connects to the Pixhawk Power Module (PM) and the PM is connected to the power distribution board (PDB).
Is this somehow different for the F450 PDB?
On the power distribution board, the power is directly wired to the battery and then goes to the Pixhawks power module, not the other way around, so wiring the UBEC also to the power distribution boards main battery power should be fine.
You would not want to wire the input to of the UBECs power to the output of the Pixhawk power module under any circumstances, you would be trying to power a 5 volt UBEC with 5 volts from the Power module and that WILL NOT WORK.