APM 2.5 and 3DR power module failure.

Hi guysRecently A friend Louis and I bought a complete APM 2.5 setup for x8 flying wingsAPM 2.53Dr radio 433 MHzUblox / Mediatek GPSAirspeed sensorAnd the 3DR power module , we completed our setup and started testing the configuration for elevon setup because of the x8 delta wing, then Louis started seeing a problem where after boot up he would try move the servos and APM would reboot.After many hours of testing he asked me to test the same on my setup and since our x8 setups are identical it would be a good test. It turns out when you move servos very slowly APM would work fine but when rolling the elevons around fast on the stick my APM also restarted.We immediately thought of power supply issue and I soldered a 5A BEC to my setup and everything was working 100% that could only mean that our setups was drawing more current then what APM power module could supply . I checked the spec sheet for the 3 DR power module and it states that the module can supply 2.25A !?Then I checked the power consumption today on my setup and stationary I was drawing 900 mah and when motor was running and moving the servos fast it was on average 1300mah , So well under the 2.25 A max limit .Does Anyone have any ideas ?This problem was now confirmed on 3 different setups !

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  • Without reading every post on seven pages,
    I assume we did find out that it's not a current limit, it's a power limit as the 2.25a is at 12V input and I'm guessing it's about 25v battery to fly an x8?

    The power drop on the higher voltage is in the order of (25-5)^2/(12-5)^2 or abut ten times.
  • Hi, i am seeing my voltage jumping around like crazy and showing about 8.8amps.....with just the usb plugged in (does it with battery also). I had to replace the voltage regulator on this unit (I12C was reading .09v) and im not sure it was doing it before. I blew the VR because i was plugging in stuff while it was powered on. I have tried two different VR's from mouser and the same problem on both. The voltage reading from the I12c port is a steady 3.3volts. Anything I can do to get a true reading?

  • I am encountering a similar problem with my APM2.5 Power Module.  I am using the same components, however I do not have an airspeed sensor.  I am using a 900Mhz 3DR telemetry radio as well.

    Everything powers up fine off the APM, but if I have my receiver connected it dies within a few moments after the APM initializes.  It seems that the Power Module is just faulty or that it is not actually capable of powering the APM, GPS, and  telemetry radio.  I have no servos at all at this point since this is a quadcopter.

    This is pretty frustrating, I paid for the hardware from 3DR assuming this was an "integrated solution" instead of buying the clones, and to invest in 3DR's contribution to the community.  However it seems I am in a bind, how am I to trust this power module with $1500 of equipment if I can't even trust it to operate under ideal conditions on the ground?  

    I have no problem using a BEC to power everything else I may add, I use the Castle BEC on all of my R/C systems.  I would happily power my APM from the BEC, but then my impression is that this conflicts with the power input from the Power Module...if I disconnect the Power Module I lose current sensing.  

    The system works fine without the PM, JP1 installed and being powered from a BEC...but of course I have no current sensing.  Should I just remove the 5V power leads from the Power Module?  On my other Arduino systems you can have 2 power sources and the board will select whichever has "higher" power, is this an option on the APM?

    Any input to this newbie is greatly appreciated.  It would be great of the Wiki/manual was updated with more guidance and scenarios about how to power the system, as clearly we cannot assume the Power Module will do the trick.

  • I hope this in on topic here..

    I want to power the input side of my APM 2.5 with 10A bec.  I also want to use a 90A Attopilot to monitor current and voltage.

    I have it set up very similar to my APM 2.0 and have used the same pins as for APM 2.0, A1 A2 for the voltage current.

    I do not get any current readings though. I have set up properly in MP for the Attopilot.

    Is there something I am doing wrong?

    I have JP1 installed for now, but I expect /plan to remove it and power output rail with a separate BEC.

    Am I doing all this right?  Maybe my Attopilot is not working?

  • I wanted to share some thoughts on my experience so far with the APM 2.5 and APM power module.  I was tempted to start a new thread, but a lot of the discussion here is relevant so I decided to post here instead.

    My setup is a 3DR Quad - C with 900 MHz telemetry, ublox GPS, and Spektrum AR8000 receiver.  I am also using the Spektrum TM1000 unit for additional telemetry.  The battery is a 4S LiPo.

    Initially, I had all flight electronics (no servos) powered from the APM, which was in turn powered from the APM power module.  Upon powering everything up on the bench, I noticed that the measured battery voltage through the mission planner was jumping around substantially - as much as a full volt from the high end to the low end.  The problem went away when I disconnected the TM1000.  I thought perhaps I had an EMI issue, but when I powered the TM1000 via one of the ESC BECs, the jumpy voltage problem did not return.

    I also observed that when I plugged or unplugged other items such as the GPS or 3DR TM unit, the measured voltage also changed by a small but significant amount. Adding devices which draw more power (in a steady manner) was causing the displayed voltage in the mission planner to increase - by perhaps a tenth or two of a volt.

    Next I started probing with the DMM, and observed that at the PM jack on the APM, the supplied voltage measured about 0.02 V lower when the GPS and 3DR TM unit were plugged in.  The voltage sense wire, however, was perfectly steady.  This is significant because the voltage sense wire is approximately 1/10 of the flight pack voltage, so a 0.02 V change in the reference voltage will correspond to approximately a 0.2 V change in the calculated flight pack voltage.  I believe that this change in reference voltage would also affect other analog values measured by the APM, but I have not investigated to confirm that.

    Notice that I also said the PM's voltage divider is "approximately" 1/10.  The mission planner has this entered (and the textbox made readonly) as exactly 10.000 (I believe it was to the 3rd decimal).  In actuality, my PM appears to be dividing by approximately 10.18.  I was able to alter the VOLT_DIVIDER parameter accordingly in the advanced parameter list.

    Now, back to the jumpy behavior when the TM1000 is powered via the APM. The TM1000 appears to transmit its data in a short burst on the same channel as the most recently received frame from the DX8 transmitter, in a timeslice immediately following said frame (I've investigated this briefly with a USRP).  Obvious this type of intermittent transmission will cause intermittent power consumption.  So I plugged the AR8000 and TM1000 back into the APM power and put a scope on the power module jack again.  The supply voltage had intermittent spikes of approximately 0.3V amplitude peak to peak.  Obviously this will wreak havoc upon analong measurements, at the very least.

    My solution to the problem was simply to power the AR8000 and TM1000 from an ESC BEC rather than the APM.

    However, I wanted to put forth some suggestions for the community to consider and provide feedback on:

    • The APM Power Module could possibly be improved to provide more consistent voltage levels (also, the wires are pretty damn thin - this may be part of the issue).  A voltage drop of 0.02 V doesn't seem like much, until you multiply it by 10.
    • The voltage divider and Amps/Volt value in the mission planner should be editable from the Battery Monitor page directly by default.
    • Instructions to measure these multipliers should be provided for those users interested in a more precise calibration of battery values (I realize I could contribute this, but I at least want to discuss it first).
    • Users should be aware that adding or removing load on the APM's power supply will affect the calibration of analog measurements.
    • Any devices (not just servos) which consume power in an intermittent fashion should NOT be powered via the APM.
    • The TM1000 is specifically a problematic device, which would not necessarily be obvious at first.  Some filtering to absorb the transients from the TM1000 may be worth investigating.

    And lastly, I found on the page http://code.google.com/p/arducopter/wiki/AC2_Current the statement (emphasis added):

    Note for ArduCopter users: you must remove the APM's JP1 jumper when using the Power Module so your electronics are only powered from the Power Module's onboard regulator and not from your ESCs. You can leave the jumper present if you are using "no-BEC" ESCs (the jumper's presence does not matter in this scenario). The two-wire PDB power cable should still be connected to the APM's output pins, as this is the ground connection between the APM and the ESCs.

    and I'm not sure this is the case.  The 3DR ESCs have a very low impedance (zero as far as I could measure with a DMM) between input ground and BEC ground.  I suppose this might not be the case for all ESCs, but I don't know.  We might want to revise this bit on the wiki.

    Any alternate analysis, thoughts, comments, are welcome of course.

    • Hi, i am seeing my voltage jumping around like crazy and showing about 8.8amps.....with just the usb plugged in (does it with battery also). I had to replace the voltage regulator on this unit (I12C was reading .09v) and im not sure it was doing it before. I blew the VR because i was plugging in stuff while it was powered on. I have tried two different VR's from mouser and the same problem on both. The voltage reading from the I12c port is a steady 3.3volts. Anything I can do to get a true reading?

  • I don't know who started the crazy idea of putting multiple 7805 linear regulators into ESC and not providing any heatsink.

    ESC with linear UBEC is simply a really bad idea, we don't need more heat in the ESC and the wiring adds to ground loops and increases the chance that 1 failed ESC takes out everything.

    Here is a typical ESC BEC which claims to provide 3A at 5V, yellow arrows point to 2 x 7805, red arrows point to ALL the tiny copper that is in effect NO HEATSINK. If one unwisely tried to draw 3 A from these it would create 22W of heat in total, the 7805 cannot handle 11W each with no heatsink, it would likley get hot enough to unsolder itself!


    On the 3 pin cable from ESC I disconnect all the black and red wires from all the ESC, reason for disconnecting the Black wire is to avoid Ground Loops, I only connect the white wire [Signal] to APM 2.5

    I use a low noise switching regulator to power the APM 2.5, Receiver, 3DRadio and GPS. Switching regulators cope well with a brown out [unless you load them to the max] when I disconnect the Lipo, the output LED on the switching UBEC as well as APM 2.5 LEDs stay lit at full brightness for another 3 or 4 seconds, so that would cope with a brown out.

  • Servos can draw a lot of current for as tiny as they are, anywhere from 1A to more than 5A for each servo. A single higher end servo could easily draw more then APM power supply is capable of handling. If the APM power supply was powerful enough to cover all the bases it would cost way more, weigh a lot more, and generally be overkill for most people. Get a good BEC to handle the servos and get to flying!

  • The really excellent Opto 18 and 30 amp optically isolated ESCs provided with the DJI Flamewheel ARF kits have a great reputation for longevity and do not include BECs.

    The Castle Creation 5-10 amp Switching BEC recommended by Jack is superior in every way to the linear BECs found in most ESCs in any case.

    A switcher can achieve consistent efficiency in excess of 90 percent.

    The linear BECs are lucky to average 50 percent.

    On our multicopters it is possible to generally parallel multiple (linear) BECs as found in the ESC's without problem, but they will not produce more peak power than a single BEC the only advantage is that in case of the most common failure one of the other BECs can pick up the load. Unfortunately in the second most common kind of failure the failed BEC can take out one or more of the other ESC's as well. So to cut the extra red wires or not is kind of a crap shoot.

    You absolutely cannot parallel switcher BECs however, one to a customer only.

    Putting on a sizable capacitor will definitely increase peak short term load capability and will smooth "sag" in any case.

    I don't know if the new 3DR power supply is linear or switcher, but if you have a decent size switcher BEC anyway you are probably better off running everything from that.

    Two separate power supplies are just 2 separate ways for something to go wrong. Not going to be doing you much good if the APM and receiver are still working and the rest of your plane isn't. - I guess the final flight log!

  • Do NOT power anything else but the APM and daughter boards with the power module. You may want to consider running a power line directly from a regulator over to your RX receiver. I had three different issues with my APM. One of which did not end very well. I'm attaching my Tlog data. You can clearly see in the logs a power dip in Vcc. At the same time you can see a spike in current_battery. This is consistant across all three of my logs. 

    2012-12-09 10-27-47 crash.tlog

    2012-12-21 21-25-28.tlog

    2013-01-05 12-53-53.tlog

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