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Allegro acs756 current sensor for arducopter

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

allegro current sensor

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

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

arducopter, current, sensor

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Comments

Alexey Kozin November 20, 2012 at 11:28pm

many thanks Andrew,
unit of measurement offset in volts, the range of values from 0.00 to 5.00
by the way this applies to standard sensors to calibrate the zero value
Developer

Andrew Tridgell November 20, 2012 at 6:34pm

Thanks Alexey! I've added your change in for the next release.
Alexey Kozin November 13, 2012 at 10:43pm

dont calculate cf and rf

it may be

rf = 1KOm - 3 KOm

cf = 1 - 4.7 microfarads

rfcf filter needed for accuracy measurement of "average current"
Rick Eis November 13, 2012 at 9:53pm

Alexey,

Awesome job on the voltage regulator!

So did you build as in the schematic posted above and if so, what did you use for Cf and Rf ?

Rick
Alexey Kozin November 8, 2012 at 11:20am

new value amp_offset used for tune input voltage on current sensor port "a1" with "zero current" allegro sensor with "zero current" have about 2,5 volts output

amp_per_volt used too, for calibrate sensivity

for +-100A allegro chip it is 40.0

for +-50A allegro chip it is 20.0
Andy November 8, 2012 at 6:04am

so the only vlaue that we have to determine is the "g.curr_amp_per_volt" am I right?
Alexey Kozin November 7, 2012 at 7:16pm

im tested with apm2 connect all 3 pinsto port a1

Gnd-gnd

+5 to +5

vout to signal
Carl Campbell November 7, 2012 at 12:26pm

Just to clarify the Ears are soldered to the + leg of the connectors with the - leg straight through. And looking at the label side, it is wired + - S for the connection to that APM?
Yuan Gao November 7, 2012 at 11:49am

Allegro current sensors are great! I started using them in my final year engineering undergraduate project, and haven't turned back since. They're affordable, and just as accurate as current transducers more than ten times their cost. (An RC filter on the output is useful)