Unable to read voltage - not sure how to troubleshoot

Hi All,


I am having an issue with the voltage sensor – I just can
not seem to get it to read a voltage. It always displays 17.8 volts. I have installed
an AttoPilot Current Sensor Board. I am using the monitoring number 4 (current
and voltage). I can get a current reading which is working fine (could be 15%
out). The voltage on AN0 is connected directly to the battery so I am not using
the AttoPilot for voltage sensing.


I have a 3.9K resistor installed and if I use a multimeter
to check the resistance between ground and the AN0 pin I get 13.9K which I believe
is correct. Because there is a 10K resister on the AN0-3 pins.


It doesn’t matter what voltage I put in to the system it doesn’t
change the read out in the current test in the CLI. I have tried 2s and 3s LiPo
packs. I have also tried mode 3 which is just total battery voltage on AN0 but
I get the same results.

I am not sure who to troubleshoot this.



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  • Hi Guys

    I have the same issue as Simon.

    After upgrading my APM 1280 to a 2560 a few month ago, I have also noticed that the voltage sensing was not working as Simons says.

    I purchased an Attopilot voltage and current sensor and still the voltage was not being read correctly. I notice that the current sensing works ok so I changed my current and voltage leads around so that the current is sensed on AN0 and the Voltage is sensed on AN1. Now the voltage is sensing correctly and the current is not sensing at all. I have now set the set the Voltage to AN1 and current to AN2 in the advanced parameters list in Mission Planner and all seems to be working fine now. 

    I will also check with my old APM 1280 and see if the AN0 works just to confirm that the fault is on the APM 2560 board and not the OIlpan as Simon has stated as well.



  • Hi All,


    I have been doing some testing - I have 2 APM and 2 Oilpans, both oilpans work fine however only one APM works. The 1280 APM works and the 2560 one doesnt sense the voltage.


    How do I troubleshoot to APM.





  • With the standard code, the current sense output is supposed to be connected to AN1.  Have you done that?
  • Moderator
    I don't have battery monitoring hooked up yet- it is next on my list (should have been first). But, I see you mention the "Current" test. Do you want to use the "Battery" test instead to get what you're looking for? (Again, I haven't done this yet, and maybe it's not what you're after, but I thought I'd ask.)
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