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suspected power issue when system is powered from 3DR power module

Posted by Mike Evers on November 6, 2014 at 6:24am

I would like to raise a concern I have about the 3DR power module. I have completed my hex (900mm) setup and have done around 10 flights. I am running 2x 4S 5000 mAh in parallel with 2814 770kv Tmotors 13x4 props APM 2.6 with V3.1.5 FW and no servos connected. I managed to do 2 successful autotune but I am not happy with the performance. I noticed when I go to auto and start going through my waypoints there is a very big altitude change/drop when arriving at the waypoint and setting up the heading to the next. When the altitude drop happens the motors spin up quit hard and it is a bit scary to see this happen. I was expecting a more fluent flight behaviour. Unfortunately I erased the logs so I can’t ok back at the amp draw and how much the altitude drop is but I will make sure I get the logs this weekend.

When I landed the last 3 flights I noticed that my receiver (XPS 8 channel) shows an orange LED instead of the expected Green. Based on the Received manual it means that the voltage for the received has dropped below 4.4V I can’t tell how much below 4.4v, how long and how many times… I hope I can find more accurate details this weekend since I am going to install a TattleTale and compare them to the APM logs.

The TattleTale is a tiny and lightweight device that plugs into a empty receiver channel (or through a Y-cable). This device measures the input voltage and displays the lowest voltage threshold that was captured after being powered on. With a programmable acquisition time of 1ms to 100ms, even the shortest voltage sags can be detected!

The tattletale has helped me in many occasions when I am facing an abnormal behaviour in my Heli FBL or Fixed wing power setup. I strongly recommended this product from XPS.

My question is in regards to the power module performance:

-          Shouldn’t the 3DR power module be able to power my APM 2.6 in my current config? I am surprised that the voltage of the power module dropped below 4.4V.

-          Can a voltage drop to or below 4.4V that was registered by my receiver cause the behaviour that I am seeing on my Hex?

-          I was planning to cut the red wire from the power module going to the PM port and connect it to an external BEC so that the APM + Received get powered from the BEC instead of the power module. Does that make any sense?

- should I get a new power module and try that out?

All suggestions are welcome…

Thanks a lot,

 

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Tags: 26, bec, apm, module, power
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  • Admin
    Thomas J Coyle III November 6, 2014 at 6:31am

    @Mike,

    You need to download either the tlog or the data flash log from the APM2.6 and take a look at the hardware voltage parameter to see what voltage was being supplied to the APM from the PM during the flight.

    Regards,

    TCIII AVD

    • Mike Evers > Thomas J Coyle III November 6, 2014 at 5:42pm

      Hi Tom,

      Thanks for your reply. I remember I had the logs but cleared them from my APM. The reason was since I was not able to open them up.

      I got the following error:

      Log browse will not function correctly without FMT messages in your log.These appear to be missing from your log.

      Not sure what there error means and how to avoid it in the future.

      I checked on my laptop and found the logs this morning on my laptop under:

      C:\Program Files (x86)\APM Planner\logs\HEXAROTOR\1

      .I have attached them so you can have a look at them. Maybe you know a way around  the error message.

      I will perform some more tests tomorrow morning and see if I can upload the logs from tomorrow's flight so hopefully those will be able to help out more.

      Thanks again for you help.

      2014-11-02 17-54-02.tlog.jpg

      2014-11-02 17-54-02.tlog

      2014-11-02 17-54-02.rlog

      • Mike Evers > Mike Evers November 8, 2014 at 4:06am

        I did some tests this morning.

        1. 1x 4S 4200 mAh Hyperion battery (480 gr) and no camera gimbal. The result was great. I was able to fly in auto without having the initial issue that I was reporting. When I landed the LED on the Tattaletale that was plugged in my bat port on my RX was GREEN blinking. This indicated that the voltage never had dropped below 4.5V I ran the auto analysis and this is what I got:

         

        Log File C:/Program Files (x86)/APM Planner/logs/2014-11-08 08-22-57.log

        Size (kb) 983.5517578125

        No of lines 14574

        Duration 0:07:27

        Vehicletype ArduCopter

        Firmware Version V3.1.5

        Firmware Hash 3c57e771

        Hardware Type APM 2

        Free Mem 1206

        Skipped Lines 0

         

        Test: Autotune = UNKNOWN - No ATUN log data

        Test: Balance/Twist = GOOD -

        Test: Brownout = GOOD -

        Test: Compass = GOOD - No MAG data, unable to test mag_field interference

         

        Test: Dupe Log Data = GOOD -

        Test: Empty = GOOD -

        Test: Event/Failsafe = GOOD -

        Test: GPS = GOOD -

        Test: Parameters = GOOD -

        Test: PM = GOOD -

        Test: Pitch/Roll = GOOD -

        Test: Thrust = GOOD -

        Test: VCC = GOOD –    <<<

        1. In my second test U used 2x 4S 5000 mAh batteries (1150 gr) and 1  camera gimbal with Hero 3 (270 gr) This was an additional 940 gr. I flew and found the exact same behaviour what I initially reported. When switching to auto the hex couldn’t hold it’s altitude very well. When switching to auto, it showed a very aggressive flight behaviour going to WP1 , Alt was set to 35m and I managed to see around 80+ m on the HUD  during flight when it reached WP1.

        I had setup autotune on one if my switches but was unable to get into autotune mode.

        After my first flight seeing the behaviour with 1 battery and no gimbal I kind of suspected that the additional weight was the cause of all of this.

        When I landed the Tattletale was blinking yellow. This indicated that the voltage on the RX had dropped between 4.5V and 4V. I checked the log and the min voltage (Vcc) shows: 4.28V

        I ran the auto analysis and this is what I got:

         

        All looked the same except for this:

        Test: VCC = WARN - VCC min/max diff 0.68v, should be <0.3v

         

        Based on the 2 flights performed and the limited log analysis I can perform it looks lik eteh additional weight is the cause of this. I should probably run autotune again with the 2 battery and gimbal installed.  The Vcc reading still doesn’t look good from a power module point of view:

         

        http://store.3drobotics.com/products/apm-power-module-with-xt60-con...

        The specs on the web show:

        Switching regulator outputs 5.3V and 2.25A max

        I am not sure how the Vcc voltage can drop so low when it just powers the APM 2.6 and my RX.

        I have attached today’s logs in case you can do some further analysis and see if there is anything else that you can find.

         

        My plan at the moment is to run autotune again and see how it goes. If it is not givig me the right results compare to flying with 1 battery I might upgrade my per setup to 6S 15” props. Maybe using T-Moter NM3508-380Kv or

        Can there be a negative effect of over powering my setup?

        Thanks a lot…

          

        Flight 1 1x 4S 4200 mAh.log

        Flight 2 2x 4S 5000 mAh.log

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