I have noticed in the forum a number of people advising the connection of ground (negative power) of all their ESCs to the APM. In some cases some people are also connecting multiple 5 volt lines to the APM in the hope of providing redundancy of the 5 volt line. In my opinion both these practices can lead to intermittant issues that could cause your copter to occassionly behave erratically, and at worse damage your APM (as connecting multiple ESC grounds to the APM can create ground loops). Ground loops will create a noisy and unstable ground for the APM, which is the last thing you want with sensitive gyros and accels. The random issues that ground loops/bad power can lead people to incorrectly assume that there is something buggy with the software, causing unnecessary work for the developers and testers.
Ideally a seperate, single BEC (5 volt regulator) should be used to power the APM as the 5 volt line from an ESC that is also powering a motor will get very hot, causing the 5 volt line to become noisy and possibly brown-out/shut-down in flight. The BEC should not get so hot that it is uncomfortable for you to keep your finger on it for more than a couple of minutes with APM+GPS+Xbee etc connected. If so, a BEC with a larger heatsink or a switch-mode BEC should be used. In addition using a seperate BEC also ensures that the APM does not share a noisy ground return of an ESC.
I think a lot of the intermittant and unexplainable issues people have had can be resolved by ensuring the power supply and powering wiring topology is sound to begin with.
Does anyone know who contact about having documentation updated to reflect the above?
sweet _and_ cheap ;)
I tried this. Use a bec to power the apm. Then only signal wires to the ESC's and I can say that they turned in little ovens.
So I reconnected the -wires again and all is well again.
ok, so now I'm confused again :))
Sorry man, I think it is my fault. I'm speaking about the jdrones esc's. Should have read the whole tread...
Hmm, I'm certain it works with grounds connected, I'm uncertain it won't fry when I touch it :)
And I want to comprehend it, only then can I blame myself when it blows up instead of blaming all of you, and only then am I comfortable passing this knowledge to other confused souls.
I have my ArduQuad flying, but I am really confused about powering the APM 1.4 / 2.0, and in need of clarification for powering my custom Hexa/Ardu build. The parts I have:
1. Diydrones Hexa PDB
2. Dimension 5V / 3 amp BEC
In the PDB instructions there is a section describing the soldering of the APM power wires, and near the end of the document is says: "Finally solder in the small two-wire cable into the small holes marked “To APM” “+” and “-“, again with the red wire into “+” and the black wire into “-“.".
Should I instead solder the BEC into this location? I don't know if this +/- connection on the PDB is being being power from the big battery leads, or from one of the ESC/BEC built into via the right angle headers?
Will the RC Receiver still be powered from the APM, through this BEC?
Also, I am concerned about getting the grounds right. If I use the stand-alone BEC will I have the right ground paths for all to work?
Thanks for your note. I still have a few questions. BTW, I am NOT using opto-isolated ESCs.
The 5 volt + / - output on the PDB, how does it produce output of 5 volts? Is there some kind of conversion within the board itself or does that 5 volts come from one of the plugged in PDBs? I just don't see how that output becomes 5 volts, when my 3S or 4S batteries are plugged in.
Really confused here: you say "The "APM (-)(+)" on the PDB is a 5 volt output, which you connect directly to your APM. You then connect only one 5 volt BEC to the right angle header pins. "
Then you say "A stand-alone BEC connected in the way describe above will be fine (having the PDB solves ground related issues to do with incorrect wiring). "
I am not sure which one you are suggesting I should do, or which one is recommended. Sorry to be thick.
>>Lastyl If you have servos, powers these by a seperate BEC, independant of the PDB.
OK, I have the UDrones camera mount with roll/pitch servos, and according to the Ardu wiki I simply plug those servers into the receiver 1/2 positions (http://code.google.com/p/arducopter/wiki/AC2_Camera). Can you explain why you are suggesting use a separate BEC for such servos?
how many amps for copter or plane with all the bells & whistles
Again, thanks for educating. I will do as you suggest, draw things up and post.
Perhaps in addition to advocating star grounding topologies, the idea of additional power supply rail decoupling for the APM might be in order for more complex wiring schemes. For example, I added a 10uF tantalum to my APM just to make sure the 5V line has a better chance of staying clean. Bypassing that with a good 4700 pF ceramic might not be a bad idea either, considering the highly complex noise environment in which these things operate. (my apologies if this has already been suggested)