I just received a new Pixhawk yesterday and spent yesterday exchanging it with my APM 2.5 in my 3dr quad… I have bench tested it and all is functioning well…
Radio TF8g ,Futaba 6203 SB
FW 3.1.1rc1
MP 1.2.93
With the APM, I used RC control for my gimbal for manual pitch and roll on channels 9 and 10… I was glad to learn that the Pixhawk aux outputs 1 and 2 correspond to those channels… I have set 9 and 10 for RC passthru (1)… BUT, the gimbal locks up with extreme positioning… What am I missing?..
In my case I connected the servo to Aux Out 3, configured RC11 for the tilt and RC6 (you can use CH9, just make sure the Pixhawk is seeing the channel in radio calibration).
Can someone from 3DR please clarify how to power servos from the Pixhawk; If the Pixhawk is being powered from the power module is it safe to connect servos to the servo output ports and have them powered from a BEC also connected to an output port? In this case, is the Pixhawk being powered from the PM or the BEC? Additionally, If the servos were to draw more current than the BEC can provide, would the Pixhawk brown-out or would the servos die but the Pixhawk switches over to being powered by the PM?
I believe the Pixhawk has a 3-way power controller, and can take power supply from either the PM input plug, servo rail, or USB but I am yet to find a diagram or function block showing how this works.
Is there a schematic for the power circuitry?
On the ETH Pixhawk website it states:
Servo rail input (4.1V to 5.7V) UP TO 10V FOR MANUAL OVERRIDE, BUT AUTOPILOT PART WILL BE UNPOWERED ABOVE 5.7V IF POWER MODULE INPUT IS NOT PRESENT. though this doesn’t seem to make anything much clearer in regards to my questions.
I have posted in this thread though I have decided to make a new one as my questions are not just for the AUX outputs and the original thread has since been marked as SOLVED so I’m not sure if it will be checked by 3DR staff. This topic is obviously very important for fixed wing users and those who wish to use gimbals on their multirotors.
[quote]Can someone from 3DR please clarify how to power servos from the Pixhawk; If the Pixhawk is being powered from the power module is it safe to connect servos to the servo output ports and have them powered from a BEC also connected to an output port? In this case, is the Pixhawk being powered from the PM or the BEC? Additionally, If the servos were to draw more current than the BEC can provide, would the Pixhawk brown-out or would the servos die but the Pixhawk switches over to being powered by the PM?
I believe the Pixhawk has a 3-way power controller, and can take power supply from either the PM input plug, servo rail, or USB but I am yet to find a diagram or function block showing how this works.
Is there a schematic for the power circuitry?
On the ETH Pixhawk website it states:
Servo rail input (4.1V to 5.7V) UP TO 10V FOR MANUAL OVERRIDE, BUT AUTOPILOT PART WILL BE UNPOWERED ABOVE 5.7V IF POWER MODULE INPUT IS NOT PRESENT. though this doesn’t seem to make anything much clearer in regards to my questions.
+1. This is an essential piece of missing information for Pixhawk.
I learned that painfully after I spent two days troubleshooting why the RC9 to RC11 AUX ouputs did not trigger my IR device for my SONY NEX : it was because the AUX outputs do not provide enough power to external devices, even those not consuming a lot (I just have my receiver and this IR trigger device).
Problem was solved when, in addition to the power port being powered by a BEC, I also added a BEC to the AUX outputs rail. (this would have not been the case for APM which I used in the same configuration with only one BEC powering everything)
Hi Nick, I connected a second BEC directly to the IR device that is connected to AUX2 (RC10) of PIxhawk; indeed Pixhawk AUX2 was unable to provide enough power for this IR device although it does not consume much : just a IR led that is turned on once for 1/10th second (thus much less than a servo).
I’m even worried now that my receiver (FrSky X8R) connected on the Pixhawk RC in shall not get enough power, but so far it seems ok.
In other words, I would not connect any device requiring power to the Pixhawk outputs. Maybe add a BEC input on the Pixhawk rail to power your extra devices?
I will add a couple of points from my Pixhawk experiences of the last few weeks.
Do NOT feed your BEC to the servo rail (on Pixhawk) to the RC Input Port!! You will short out the IO board portion, requiring replacement. For whatever reason, I had the BEC from my ESC going to my receiver, which then fed the servo rail. Not good. 3DR was great, though.
Using a FrSky D8R-II+ receiver sending it’s own battery level back to the Taranis transmitter, and having six (6) volts from my BEC to the servo rail, the receiver was only getting ~ 4.86 volts. When I added a connection for RSSI, the receiver voltage jumped a full volt, to approx 5.85.
The servo rail in general, and Especially the RC input port, are very particular about the power levels, and you must investigate to your own satisfaction it’s ability to provide the power your systems require.
Nick and Chris, I’m the Director of Software Engineering for 3DR
If the Pixhawk is being powered from the power module is it safe to connect servos to the servo output ports and have them powered from a BEC
In this case, is the Pixhawk being powered from the PM or the BEC?
Yes it is safe. The Pixhawk has a power monitor that picks the Power module first, the servo rail second, and the USB input third.
Pixhawk is designed to be powered off the servo rail but only up to 5.7Volts. What we are seeing is that on some systems the servo rail is really noisy and the noise can be sufficient to damage the Pixhawk. Pixhawk is dutifully shutting off to protect itself. We have changed the description on the website to recommend that people use a Zener diode across the rail to prevent the servo spikes from going above 5.7V
From 5.7 - 10 volts the output part of the Pixhawk will remain powered. This will allow a manual override on planes in the event that the Pixhawk does fail. This feature is still being worked on in software but the hardware is in place to allow the feature.
I merged these topics together so the information about powering the servo rail is all together.
The RCIN connection will power a receiver the rest of the servo rail must be powered from some external source. The Pixhawk will not power your servos.
AIL, ELE, RUD servos connected with all three pins to labeled connections
CH5 is connected to a Castle 10A 5v BEC, powered by a separate 11.1v battery
Is this a correct method of connecting, and will it provide adequate power to the servos?
Are the PWM outputs also powered by the same servo rail?
In the event of a dead flight battery or faulty power module, will the BEC input still be able to power the Pixhawk, R/C Rx, and servos?
[quote=“Craig3DR”]I merged these topics together so the information about powering the servo rail is all together.
The RCIN connection will power a receiver the rest of the servo rail must be powered from some external source. The Pixhawk will not power your servos.[/quote]
This is what I’m planning on doing with my Skyhunter Pixhawk setup. Power module connected, but also powering 5v to the servo rail via a Castle 10A BEC. This shouldn’t overload the servo rail, but will provide redundant power, and adequate power to all the servos.
What zener diode should be used? A part number? Specs?
With what polarity should the zener diode be connected on the servo rail? ( the wiki is not showing any connection diagram, just a picture of an unknown zener diode)
I used this diode and it got extremely hot with a 5v UBEC.
Is this the wrong one?
It has the same part number but it looks different than the one in the wiki.
1N5339[b]B[/b ]is the 5 Watt type. Without the B it’s only 0.5 or 1W, which is the one you see in the Wiki.
If it gets hot, you either connected it wrong or your BEC constantly spits out more than 5.6V
It’s connected in blocking direction, means cathode towards plus and anode towards minus. Only when the voltage on the bus exceeds 5.6V, the Zender breaks through and thus reduces the voltage.
Besides I bought the same 10 pack from the same guy .
This model you crimp with the side which has the ring towards the middle (+) pin and the side without the ring towards the outer (-) ping of a servo plug.
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