This question is both for a pixhawk and an APM 2.6 (I have both).
Short question is that I have 2 12V lipos. I'd like the first one to run the motor and the second one to run the flight computer, servos, camera, and OSD.
This way if the throttle battery runs out of juice, the 2nd battery can still control the flight computer which in turn can talk to servos that are also powered by the 2nd battery (and of course the OSD and video are still running too)
I know that the APM 2.6 (and I'm guessing pixhawk too) doesn't provide enough current on the 5V outputs to run servos.
Currently I have a 12V lipo connected to an ESC that acts as BEC and feeds power to the pixhawk/APM2.6 via the throttle input.
At the same time, pixhawk/APM2.6 also gets power from the power module.
I'm not sure how many amps the power module can provide to the arduino, but looking at the thin wire sending power to the arduino, I'll guess very little :)
Now, I have a 2nd 12V lipo that powers a camera connected to a miminOSD.
The board has a 12V to 5V voltage regulator too, but I'm also going to guess you can't source enough current from it to power servos either.
Also, I've read that I should consider powering the miniOSD from the 5V side and not the 12V side because the 5V voltage regulator is noisy.
(google rctimer-minimosd-5v-mod)
Questions:
0) Is my APM 2.6 currently getting 5V current from my ESC and passing that on to the 5V servo output, therefore providing enough amps to control the servos?
1) what is my best way to power at least the pixhawk or APM2.6 from the 2nd battery?
2) doing #1 would be good, but if the servos won't move, I guess it's not that useful :)
3) I assume I should disable the 12->5V voltage regulator on the minimOSD since it's noisy and won't help power my servos anyway
Does it mean that I effectively have to buy a BEC, in other words a 3rd device converting 12V to 5V, to make things work like I'd like?
Isn't there an APM power control board that can act as a BEC which has enough current to power servos?
Or any other way to do what I'm trying to?
Thanks.
Replies
Thanks for sharing your setup, very interesting.
Hi,
first of all you could read this: Warning-about-helicopter-power-supply
and there is some interesting information
here Power supply
and here Hints regarding Servos
#1 you MUST provide regulated 5V to APM/Pixhawk. as long as possible
#2 you MUST NOT use the 5V for APM/Pixhawk for anything else because of possible brown-outs.
#3 you should have a backup battery to power APM/Pixhawk and RC in case the LiPo or BEC quits
Here is my setup as a possible compromise depending on your priorities:
I removed the JP1 Jumper.
My RX can take 8.4V and reports the voltage via telemetry. I want redundancy as well and use a 4 cell eneloop 2000mAh for that (the eneloops keep there voltage during storage much better than usual NiMh) because I use 6V servos.
Therefore I use the balancer connector to get 2s (8.4V) from the LiPo and connect it to one anode of a MBR2545 rectifier and the eneloop goes to the other anode of the MBR2545. The cathode of the MBR2545 delivers the power to the RX.
From the RX I use a LDO (MIC29300) and 10µF to power APM/Pixhawk.
For the servos you want a setup that delivers a higher voltage than the backup battery. Most ESCs are less likely to fail if they don't have to deal with the servos. In my case I use an external 6V BEC with 6A continuous / 12A peak. The BEC and the eneloop are connected to a second MBR2545 and this power is connected to the output of APM / Pixhawk to power the servos. I use two low ESR capacitors with 4700µF/35V for buffering on the output.
This setup has the advantage that you usually have to charge only the LiPo and everything should work as the eneloop is not used in regular operation. With this setup you can i.e.power only the RX and APM / Pixhawk by connecting only the 2s balancer - no power on the ESC - for testing or warming up of electronics and GPS. You can test servos, RX and APM / Pixhawk by connecting the eneloop and still have no power on the ESC.
General warning ! If you connect the 2s you MUST connect the minus cable of the LiPo first and the plus afterwards. If you connect balancer and plus of LiPo without minus you have a good chance for expensive smoke on your equipment as strong return currents can flow through the balancer connection.
Hi Ultrafuge,
Thanks for sharing ur setup with us, I have some queries regarding my setup and i'd be glad if u cud advice on this issue.
I have a gasoline engine R/Cmodel, I intend to use two flight batteries...one(independent) for the engine power supply and the second one to power my pixhawk and servo rail which should be able to power up to 6 servos.
From the second battery(3S lipo - 12 V), i use a power module to power my pixhawk and the servo rail. since the servos require only 6V, should i use a voltage regulator to power my servo rail or is there an alternative?
Thanks in advance!!!
Anyone else?
Would anyone agree that leaving JP1 actually gives you redundant power is is a good thing?
I asked 3DR and they responded that JP1 must be removed in a dual power situation, and said it's because the servo side can somehow create brownouts on the APM side.
Since there is a zener diode to prevent exactly that from happening, I'm not too sure how that's possible, so I'm still not certain why it's there, but apparently you have to remove it.
Marc, I'm running a APM 2.5 with the JP 1 jumper removed. I use a LiFe 6.6 to power the power module, receiver, telemetry and sonar. I use a BEC set at 5.7 volts to power the output side of the APM. My FPV transmitter and camera gimbal are powered by a small 3s 900Mah LiPo. This has worked fine for me for a year now flying a traditional helicopter.
Regards,
David R. Boulanger
So you're running with 3 batteries? Ok, I guess that's one way to do it :)
I was reading more about the power distribution on the APM 2.5/2.6 and I understand that with a power module, I can remove JP1.
However if the 5V converter in the power module fails, with JP1 removed, then the APM would die in flight.
Since there is a diode preventing current from the APM to the servos connected to output, am I not better off leaving JP1 on, so that the APM can get power from both sides (BEC on output via diode) and power board input?
Thanks, Marc
Marc, Yes. If my power module fails I'm screwed. I'm not sure about leaving JP1 on.
Regards,
David R. Boulanger