I have plugged all of my servos for my ailerons, rudder, elevator, and motor into the Pixhawk's servo rails. I am trying to set up my Pixhawk system within a rather large UAV airplane, and for some reason I am not getting power to the servos when I turn on the system and try to move the sticks on my transmitter. I have uploaded the firmware and the transmitter and receiver are bound together. Any thoughts? I read that I need a separate power input directly onto the servo rail, but I just wanted to make sure.
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So the problem that I had was that I didn't make the connection between the ESC/Throttle connector and the power for the servo rail: The servo rail is indeed NOT powered by the Pixhawk. All your power on the servo rail comes from the connection that you made with the Throttle connector, which should already be connected to an ESC/BEC (a lot of time these are in the same unit, I think...). So if you have an ESC that controls your throttle, that throttle connector will also give power to the rest of the servo rail when you plug it in.
I was confused for the longest time, so I feel really good to finally know this is true :-P
Make sure you include the recommended zener diode or you may experience unexpected Pixhawk reboots.
Regards,
TCIII AVD
Andrew A > Thomas J Coyle IIIApril 12, 2015 at 7:35pm
@TCIII AVD
Thanks a lot for the response! The link definitely helped, and I am well on my way to flying this thing :-).
I am still confused on some things though.
1) I have had a while to work on it, and, based off of the powering instructions in the link you gave me, it says quote "Pixhawk does not supply power to the servo rail" end quote.
However, when I plugged in my 11.1 V, 1800mAh, 3 cell battery (not going to be the actual flight battery, in case anyone asks) to the power module, I was able to figure out how to fun my servos without ANY secondary power supply plugged into the servo rail directly (i.e. ~5 volt power supply that would be plugged into the servo rail's power and ground pin).
First I just plugged in the battery to the power module, let the Pixhawk warm up and give me the beeping sounds indicating it is OK, and then I held down the external safety switch. Holding down this switch for a few seconds caused my servos in my airplane to activate. I was then able to move the servos around and control them with my transmitter. So, to me, that clearly goes against that specific part of the instructions that tells me that Pixhawk does not supply power to the servo rail (which I think I proved that it does). Can anyone please explain what I am missing?...
2) Also, I fully intend to use a secondary power supply on the servo rail anyway for backup in case my motor and/or ESC dies on me. So to test out the secondary power supply, I again used the same battery, but with a BEC to drop the voltage down to ~5 volts. This caused power to go into my Pixhawk, as expected, where all the lights and sounds started to do their thing. I was also able to, again, hold down the safety switch, and my servos were activated.
My main issue is this: If there are 2 (or more) places in the Pixhawk where I can plug in electrical power and run my servos off of them, is there a risk that I can draw too much current from the two power sources that both have the ability to go into the servo rail? If there is a risk of this, what would be a good way to configure my electronics so that I don't risk drawing too much power through the Pixhawk and ruining it?
Anything helps! If anyone is confused about my explanation of anything, I can supply pictures if need be ;-)
Replies
Actually, nevermind. I think I figured it out. Sorry for the confusion.
How did you solve this? I'm having the same problem as well.
Hey Jose,
So the problem that I had was that I didn't make the connection between the ESC/Throttle connector and the power for the servo rail: The servo rail is indeed NOT powered by the Pixhawk. All your power on the servo rail comes from the connection that you made with the Throttle connector, which should already be connected to an ESC/BEC (a lot of time these are in the same unit, I think...). So if you have an ESC that controls your throttle, that throttle connector will also give power to the rest of the servo rail when you plug it in.
I was confused for the longest time, so I feel really good to finally know this is true :-P
@Andrew,
When in doubt, consult the Wiki Link
Make sure you include the recommended zener diode or you may experience unexpected Pixhawk reboots.
Regards,
TCIII AVD
@TCIII AVD
Thanks a lot for the response! The link definitely helped, and I am well on my way to flying this thing :-).
I am still confused on some things though.
1) I have had a while to work on it, and, based off of the powering instructions in the link you gave me, it says quote "Pixhawk does not supply power to the servo rail" end quote.
However, when I plugged in my 11.1 V, 1800mAh, 3 cell battery (not going to be the actual flight battery, in case anyone asks) to the power module, I was able to figure out how to fun my servos without ANY secondary power supply plugged into the servo rail directly (i.e. ~5 volt power supply that would be plugged into the servo rail's power and ground pin).
First I just plugged in the battery to the power module, let the Pixhawk warm up and give me the beeping sounds indicating it is OK, and then I held down the external safety switch. Holding down this switch for a few seconds caused my servos in my airplane to activate. I was then able to move the servos around and control them with my transmitter. So, to me, that clearly goes against that specific part of the instructions that tells me that Pixhawk does not supply power to the servo rail (which I think I proved that it does). Can anyone please explain what I am missing?...
2) Also, I fully intend to use a secondary power supply on the servo rail anyway for backup in case my motor and/or ESC dies on me. So to test out the secondary power supply, I again used the same battery, but with a BEC to drop the voltage down to ~5 volts. This caused power to go into my Pixhawk, as expected, where all the lights and sounds started to do their thing. I was also able to, again, hold down the safety switch, and my servos were activated.
My main issue is this: If there are 2 (or more) places in the Pixhawk where I can plug in electrical power and run my servos off of them, is there a risk that I can draw too much current from the two power sources that both have the ability to go into the servo rail? If there is a risk of this, what would be a good way to configure my electronics so that I don't risk drawing too much power through the Pixhawk and ruining it?
Anything helps! If anyone is confused about my explanation of anything, I can supply pictures if need be ;-)