There seems to be a big, big issue with builders frying the APM 2.0.
A good many of them seem to know what they are doing. What is the problem?
I want to know once and for all how NOT to fry the APM 2.0.
It's my understanding that the APM 2.0 needs/uses 5v. It is also my understanding from the posts and submissions from the forums that supplying more or less than the stated 5v can or will cause issues.
Seems simple enough, but then why are guys having a problem?
I'm not a computer scientist or electrical engineer, so I must rely on the kind help and support from others here.
In my case I have a servo that must use 6v because of the torque. My Castle Creations phoenix Ice 50 motor controller is programmable and can supply 5v.
I also have a separate Castle Creations BEC battery eliminator. It is also programmable and can supply 4.8v-9.0v
Now, beyond the 6v servo. I am not running anything special. I plan on using the GPS, xbee and maybe the wind speed sensor.
The question is using a single 4s 5000mah lipo, what is the safe and correct way to wire the APM 2.0 so as to NOT fly it?
You might be best to just get a proper 5V servo. Messing with all that wiring can certainly increase your chances of frying the APM. You could also have interference problems and ground loops and diode burnouts or other problems. I don't think the added weight and complexity of wiring is worth it. KISS right?
It would be a real heart breaker to crash or burn out your $200 APM over a $10 servo issue.
Looking at other servos was a good idea... but I'm running into some problems.
The APM is restricted to 5v right... But I also believe it is restricted to 3amps correct?
My servo is a HS-5645MG which stalls at 157oz using 6v. The servo arm that is attached to the servo is 2.5" long.
The total aircraft weight is about 6lbs... I don't know the calculation but the torque needed is beefy.
I can drop down the voltage on powering my current servo but the torque drops to the 114oz range. So that won't work.
I could get another servo in the same size form factor that outputs 144oz torque at 4.8v. The stall amps draw is at 3amps.
I could go larger yet but the amp draw goes over 3amps which is bad news. So that puts me in the same position that I am in now where I would have to separate the power using another BEC correct?
If it is likely to draw that much current? then yes...
But if your aircraft is only 6 pounds then I doubt you need so much torque?, I have about 180oz on a warbird that weighs 30 pounds!
I would suggest that you need a servo of around 70oz torque and even that will be more than enough...
I am assuming you are talking about the elevator? if not? and another control surface then even less will be good
And it depends how you will be flying it? 60mph hard loops then 50 - 70oz will be fine
100+ mph and hard loops then you will need a little more, but if the aircraft only weighs 6 pounds it probably couldn`t handle the stresses involved in such maneuvers?
You can always ask advice at your local model shop, on what servo they recommend? as long as they know their job well..
The 5v and gnd pins are all tied together on the output rail. You can run lots of current through these rails because there's no components involved. If you notice any problems just take two lengths of wire and solder them along the rails on the underside. Or just bridge them with solder.
If the trace melted at some point you can easily just do what I said above to fix it. No chance of burning out your board.
I think I have a good plan! I'll use the motor controller to supply 5v to the APM and R/X thru the output rail via the throttle ch. The separate BEC will power the servo/s directly using the a power and ground via a Y harness.
From the APMs servo output I'll connect the just ground and signal to the servos ground and signal thus maintaining common ground for the whole system.
With this setup I hope to have more flexibility in what I can connect to the APM without limitations on the amps or voltages within reason. I'm still experimenting with the airframe and how much weight and where the CG needs to be. So I still require flexibility with the servo and the length of servo arm..
I'm totally thankful for all the responses for help... thanks guys. I'm be wiring everything up in the next several days I'll keep you all posted.
I had a similar problem, which was due to the BEC in the ESC not having any smoothing capacitors, which could drive the servo's fine but the voltage drop when all 4 servo's were under load would cause the APM to lock up and lock the servo's into position (no reboot). I ended up using a spare ESC which had smoothing capacitors to power the APM only. Both BEC's are powered up off a common connection from 3 x 3S2200mAh LiPo that gives me 20 min flight time in a Multiplex Mentor with around 800mAh remaining.
I've seen a lot of guys on in here that have cooked their APM 2.0 due to power issues.
My approach is that I run a UBEC to power just the APM 2.0 and use the aircraft's ESC to power the R/X and servos.
I run just one battery, so I have y harness on my 5000mh 4s lipo one feeds the APM and the other the ESC.
The other thing I do is that I have a switch on the APM between the battery so that any sparking while trying to connect the battery won't effect the APM. Don't know if that matters but I also like to turn on the APM after the RX has powered up.
Ive been told you'll need to isolate the APM from the ESC if running different voltages, so you don't want the ESC to feed power to the APM or the other way around. So pull the hot wires that go to and from your APM and be sure you are maintaining a common ground if you are running a single battery. This will allow for the AMP to signal the servos with out powering them.
The other way I've been told is to power just the servos with the UBEC and have the ESC power the APM and RX. In this approach you will need to just power the servos with ground and power, from the APM I've been told to use just ground and signal. So it would take a Y harness for ground going to the servo, one to the UBEC and one to the APM.
I think that the best option to power the APM is using the output rail, using both or just the input rail seems like it can cause issues with over amperage.
Anyway that's my take on it. Do come careful reading on maintaining common grounds... because that will really screw up electronics if its not done correctly.