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Allegro acs756 current sensor for arducopter

Posted by Alexey Kozin on November 7, 2012 at 11:00am

allegro current sensor

allegro.jpg?height=297&width=400


allegro2.jpg?height=254&width=400


The sensor is galvanically isolated from the circuit, but in contrast to the classical current sensor shows not only the battery discharge and charge it (eg energy recovery in airplanes)
but because of this, at zero current output, exactly half the supply voltage (for classical sensors autopilot 0) ie 2.5 volts.

to correct this misunderstanding to change firmware code



defines.h  change

#define CURRENT_AMPS(x) ((x*(g.input_voltage/1024.0))-g.curr_amps_offset)*g.curr_amp_per_volt

 

parameters.pde add

    // @Param: AMP_OFFSET
    // @DisplayName: current sensor zero calibration
    // @Description: in volts
    GSCALAR(curr_amps_offset,      "AMP_OFFSET", CURR_AMPS_OFFSET),




parameters.h  add
 

      k_param_curr_amps_offset = 193,



      AP_Float        curr_amps_offset;




//#ifndef CURR_AMPS_OFFSET   
 # define CURR_AMPS_OFFSET               0.0
//#endif

allegro4.jpg?height=400&width=340

archive with source and HEX file for quaid "x"  APM2 here

Tags: arducopter, current, sensor
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Comments

  • daniel garrow October 6, 2017 at 11:18pm

    my X8 can pull up to 531 amps so can I even use a current sensor?

  • Harald Finster March 24, 2014 at 12:53pm

    @William: sorry, very late reply - just came across your question by accident.

    Short Answer: the unidirectional versions map currents from zero to max_current to output voltages between 0V and 5V, whereas the bidirectional ones match the range from negative max_current to positive max_current to 0V - 5V.

    Thus zero current equals an output value of 2.5V.

    As your copter does not have any brakes feeding current back into the battery (I suppose ;-) ) a unipolar version of the circuit will be better for your application.

    Greetings

    Harald

  • Alexey Kozin February 5, 2014 at 10:04am

    Thanks!!!!

  • Ronny Hasse February 3, 2014 at 11:04am

    checkout 3.1.1 rc2 from github(master branch) and you have it! I have testet!

  • Alexey Kozin February 1, 2014 at 8:31am

    somebody ask Randy include this in the official firmware

  • Ronny Hasse January 30, 2014 at 12:12pm

    I have compiled 3.1.1 rc2 with AMP_OFFSET is out of the box. thumbs up!

  • William September 25, 2013 at 2:11am

    Hi, I would be really grateful if someone could give me some advice regarding the allegro sensors. My octocopter has the potential to draw a high current (about 180amps) so looking at the Allegro ACS758 200 Amp Series Hall Current Sensor, is it appropriate? Also should I get the Bi-directional or uni-directional version, I don't understand the difference. Thanks.

  • Alexey Kozin February 21, 2013 at 10:22am

    I offered Randy enable this setting in the official firmware
    he either missed my post, or ignored.
    try someone  to write about it again to Randy

    ps

    and arduplane this parameter has made​​.

  • Eric Thomas February 19, 2013 at 12:06am

    One thing to watch out for is that, in ArduCopter 2.9.1, parameters have been added and "k_param_curr_amps_offset = 193" will conflict with another parameter (resulting in the "AMP_OFFSET" value not saving to the non-volatile memory). A higher value needs to be used, like "k_param_curr_amps_offset = 199".
    --ET

  • Eric Thomas February 18, 2013 at 10:00pm

    There doesn't seem to be any sign of a new "AMP_OFFSET" parameter in the ArduCopter v2.9.1 release (contrary to Andrew's 11/20/2012 comment). Would be great if it's added soon so we don't have to keep "hacking" it in.
    --ET

This reply was deleted.