My understanding is that the Pixhawk alone shouldn’t be used to power servos – from what I could gather from looking at various wiring schematics (like below), it seems that I should use the “BEC” cable off of the ESC and connect it to any of the outputs on Pixhawk?
brunswickrc.com/images/diagram.jpg
So in essence the Pixhawk gets two power inputs: the “BEC” cable to power servos and the “POWER” input on the Pixhawk itself to power the logic board/receiver. Is that correct? Thanks.
@arandall,
When in doubt read the Wiki: http://plane.ardupilot.com/wiki/common-autopilots/common-pixhawk-overview/#powering
Regards,
TCIII GM
After reading it I was still unsure so I thought I’d ask. It seems mis-wiring things is an easy way to fry a $300 device. I guess you plug it into a PWM port? Does it matter which servo output port that the 5V, ground, and signal plugs go into? Thanks.
I would use the supplied 3DR power module with XT60 connectors and 6-position connector cable to power the Pixhawk correctly.
To power the servos you need to buy or make a power distribution board. You would then connect a BEC to the Power distro board and then connect all your servos to that. From there just split the signal wire from that power board and run it to the Pixhawk.
Thanks for the reply – what does it mean to “split the signal wire”? I guess I’m confused because the pixhawk has +5V pins for servos, but it sounds like it’s not providing power, only the signal. If that’s the case then why does the pixhawk have those pins…?
While you could make a dedicated power distribution board for the servos that’s a bit advanced for what I think is the OP’s basic question and has ended up confusing him. While it may be a good practice for some installations it certainly isn’t necessary.
The power output “rail” for the Pixhawk has for each channel, a signal pin (bottom row), a ground pin (top row) and a + 5 volts. The + 5 volts is the row of center pins. The Pixhawk itself doesn’t provide any power to this center row, you have to do that externally.
You can do this by plugging a 5 volt BEC into one of the unused output channels with the + 5 volts on the center pin. This feeds +5 volts to all the center pins.
Another way to achieve this is to use the +5 volt output from ONE of your ESCs, assuming they have a several amp output capacity (i.e., aren’t Afros or DJI Optos). If you plug in more than one + 5 volts output from an ESC they can “fight” each other so it’s usually not advised. Just remove the center +5 volt wire from the other ESCs. You only want power from ONE ESC feeding the +5 volt rail.
As an added bonus of providing +5 volts to the output rail, the Pixhawk will switch over to it as a backup power source if the Power Module fails.
As long as you pay attention to the polarity when plugging the servo connectors in, you won’t fry your Pixhawk.
