Hi guys,


3DR arducopter, APM2.5 :

during ESC calibration i noticed one of the fourth ESC (motor4) an extreme overheating. Three possibilities : ESC problem, motor problem or PDB problem on output motor 4.

I excluded ESC and motor problem by swapping the "hot" ESC by a nother ESC : this other ESC was also getting hot. Then I used PDB output n°3 on motor 4 and everyhting was fine -> this excluldes a short on motor n°4.

So obviously I have a problem with my PDB on output 4, that provokes extreme overheating of the ESC. I measured with an ohmeter the resistor between the + and - of PDB output 4. It is the same as all other outputs (so no short at that level). Plus the fact that even if the ESC overheats, the motor 4 still turns fine !


So what could be a cause on that PDB that makes the output 4 , thus the ESC4 overheat, but still driving the motor to turn fine ??? A short on the PDB ? Did I solder something wrong on the PDB ?


Please help because I have exhausted all I could test. Should I disassemble the whole thing to get a closer look at the PDB ?  What  other tests could I do on the PDB to detect an eventual issue ?

I want to avoid having to replace a PDB, not only is it more dollars to dish out, but further it is a pain to assemble and solder.



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Replies to This Discussion

Are you providing power to your APM 2.5 board from your ESCs?  Do you have the power lead from all 4 ESCs attached to the APM 2.5 board?  This is the configuration I'm using and I am having the same issue.  I am starting to believe this configuration is causing this.  Hopefully someone here can recommend a better way.

Yes, if you're using one of the ESCs to provide power to the APM and other electronics, that ESC will run hot. That's why we recommend you use the Power Module instead to power the electronics. Much more reliable.

I am using the 3dr power module. I kept the red/black connector between the PDB and the APM output rail. JP1 is off.

So this is not the problem.
Any other idea of what could be wrong ?

Just how long are your power leads?


The length they come in the 3DR kit

@Chris Anderson : if using 3DR power module, do i need to disconnect the power lead between PDB and APM output rail ?

Chris... My configuration exceeds the 90A rating of the Power Module by a little bit.  My calculations indicate that I will draw roughly 105A at full throttle (Quad with 3530-14 1100kv motors, 30A SimonK based ESCs, 6000mAh 3S 25-50C LiPo, etc.).  Each ESC has a 5V 2A BEC. What other options do I have for powering the APM 2.5 board without using the the ESC's BECs?

The 3DR power module will power the APM. You should try and disconnect the red/black wires from the PDB and see if the problem goes away. Keep in mind that the 3DR power module can power the APM, but don't add any camera servos, it can't handle both the APM and the camera servos. If you need camera servos you will need a larger BEC. I use a 5 amp BEC to power everything. I don't get the battery monitoring. So I fly with small battery buzzer attach to the balance plug on my battery.
Get a bec like Castle. Take out jp1; both sides of the apm with the bec. Take the power lead out of all of the esc cables and run them right up to the apm outputs. Sometimes noise causes the esc to send reversing signals to the motor. Fewer connections from the apm to the esc the better.
Thx for your advices.
However i want to pinpoint the root cause(s) of this PDB output 4 causing ESC overheat.
I will disassemble the quad to recheck evey solder, to recheck there are no shorts. I will also try this test: i will power ESC 4 by PDB output 4, but using the signal wire of PDB output 3. This test will tell me if the problem is on the power/Dean circuit side or rather on the motor signal drive circuit.
Will keep you posted
Update after investigation and tests:
I disassembled the 3DR quadcopter to unmount the PDB. I then checked every single solder, they were fine. I checked if there were shorts but all was ok. I checked to be sure no bare cables or connectors were touching conductive parts of the PDB or connectors, all was ok.
I did the test described in my last post, the ESC number 4 was still overheating.
I then noticed that the 3DR PDB board has a specificity for its output number 4: this is also the output of the PDB where a black & red 5V servo cable is soldered to feed the APM output rail.
I then disconnected this cable from the APM and BINGO, problem is solved !

Conclusion and summary: for all of you out there who use a 3DR power board and 3DR power module, you must DISCONNECT the red&black servo cable between the PDB and the APM2.5 output rail.

If a moderator of the arducopter wiki manual reads this,could you please add this instruction to the 3DR assembly guide ?

Bob... can you explain what you mean by "Take the power lead out of all of the esc cables and run them up to the apm outputs."?  I was planning on adding a separate 5V 5A BEC to my set up to power the APM.  This would mean I have to remove the red power lead connection from all my ESCs to the APM, correct?  Also, where is the best place to connect the BEC output to the APM 2.5?

It sounds like the BEC is overloaded. Using multiple (linear) BEC in parallel or using a larger BEC should solve the issue.


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