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AttoPilot Voltage/Current Sensor with connectors

The sensor is also available from SparkFun http://www.sparkfun.com/products/9028

SparkFun Power sensor board (Same as AttoPilot board)

The sensor provides a scaled output for battery voltage and current. The outputs are scaled for a 12 bit 3.3V ADC. Full range is 51.8 Volts and 89.4 Amps.

The connector that is wired into the AttoPilot sensor is pinned for a direct connection to the APM shield.

To prep the shield I left the first two resistor positions open (no resistors installed) and shorted the last two positions.

I installed a 3 pin header. The 4th pin from the bottom of the row is ground (the black lead). The next pin up is battery voltage (the red lead). The 3rd pin is the battery current (white lead).

I noticed that during the "test -> battery" only 1 reading was displayed and it was inaccurate.

I changed the 'sensors' file so that the battery read continues until you hit Enter to exit.

To incorporate the Power Sensor I had to modify these files:

sensors

defines.h

test

config.h

APM_Config.h

ArduPilotMega

Here are the changes I made:

sensors

#if POWER_SENSOR == 1

void read_battery(void)

{

battery_voltage1 = BATTERY_VOLTAGE(analogRead(BATTERY_PIN1)) * .1 + battery_voltage1 * .9; //reads power sensor voltage pin

battery_voltage2 = BATTERY_CURRENT(analogRead(BATTERY_PIN2)) * .1 + battery_voltage2 * .9; //reads power sensor current pin

battery_current = battery_voltage2;

}

#endif

#if BATTERY_EVENT == 1

void read_battery(void)

{

battery_voltage1 = BATTERY_VOLTAGE(analogRead(BATTERY_PIN1)) * .1 + battery_voltage1 * .9;

battery_voltage2 = BATTERY_VOLTAGE(analogRead(BATTERY_PIN2)) * .1 + battery_voltage2 * .9;

battery_voltage3 = BATTERY_VOLTAGE(analogRead(BATTERY_PIN3)) * .1 + battery_voltage3 * .9;

battery_voltage4 = BATTERY_VOLTAGE(analogRead(BATTERY_PIN4)) * .1 + battery_voltage4 * .9;

#if BATTERY_TYPE == 0

if(battery_voltage3 < LOW_VOLTAGE)

low_battery_event();

battery_voltage = battery_voltage3; // set total battery voltage, for telemetry stream

#endif

#if BATTERY_TYPE == 1

if(battery_voltage4 < LOW_VOLTAGE)

low_battery_event();

battery_voltage = battery_voltage4; // set total battery voltage, for telemetry stream

#endif

}

#endif

defines.h

#define BATTERY_VOLTAGE(x) (x*(INPUT_VOLTAGE/1024.0))*VOLT_DIV_RATIO

#define BATTERY_CURRANT(x) (x*(INPUT_VOLTAGE/1024.0))*CURR_DIV_RATIO

test

static int8_t

test_battery(uint8_t argc, const Menu::arg *argv)

{

print_hit_enter();

#if POWER_SENSOR == 1

while(1){

for (int i = 0; i < 20; i++){

delay(20);

read_battery();

}

Serial.printf_P(PSTR("Volts:"));

Serial.print(battery_voltage1, 2); //power sensor voltage pin

Serial.print(" Amps:");

Serial.println(battery_voltage2, 2); //power sensor current pin

if(Serial.available() > 0){

return (0);

}

}

#else

Serial.printf_P(PSTR("Power Sensor Not enabled\n"));

#endif

delay(3000);

#if BATTERY_EVENT == 1

while(1){

for (int i = 0; i < 20; i++){

delay(20);

read_battery();

}

Serial.printf_P(PSTR("Volts: 1:"));

Serial.print(battery_voltage1, 4);

Serial.print(" 2:");

Serial.print(battery_voltage2, 4);

Serial.print(" 3:");

Serial.print(battery_voltage3, 4);

Serial.print(" 4:");

Serial.println(battery_voltage4, 4);

if(Serial.available() > 0){

return (0);

}

}

#else

Serial.printf_P(PSTR("Battery Event Not enabled\n"));

#endif

delay(3000);

}

config.h

//////////////////////////////////////////////////////////////////////////////

// Battery monitoring

//

#ifndef POWER_SENSOR

# define POWER_SENSOR DISABLED

#endif

#ifndef BATTERY_EVENT

# define BATTERY_EVENT DISABLED

#endif

#ifndef BATTERY_TYPE

# define BATTERY_TYPE 0

#endif

#ifndef LOW_VOLTAGE

# define LOW_VOLTAGE 11.4

#endif

#ifndef VOLT_DIV_RATIO

# define VOLT_DIV_RATIO 3.0

#endif

#ifndef CURR_DIV_RATIO

# define CURR_DIV_RATIO 3.0

#endif

APM_Config.h

// Battery monitoring

#define POWER_SENSOR ENABLED

#define BATTERY_EVENT DISABLED

#define BATTERY_TYPE 0

#define LOW_VOLTAGE 9.6

#define VOLT_DIVRATIO 15.7 //AttoPilot sensor voltage ratio (Minor adjustments to these values

#define CURR_DIV_RATIO 30.35 //AttoPilot sensor current ratio allow calibration to desired accuracy)

ArduPilotMega

// Sensors

// --------

float airpressure_raw; // Airspeed Sensor - is a float to better handle filtering

int airpressure_offset; // analog air pressure sensor while still

int airpressure; // airspeed as a pressure value

float battery_voltage = LOW_VOLTAGE * 1.05; // Battery Voltage of total battery, initialized above threshold for filter

float battery_voltage1 = LOW_VOLTAGE * 1.05; // Battery Voltage of cell 1, initialized above threshold for filter

float battery_voltage2 = LOW_VOLTAGE * 1.05; // Battery Voltage of cells 1+2, initialized above threshold for filter

float battery_voltage3 = LOW_VOLTAGE * 1.05; // Battery Voltage of cells 1+2+3, initialized above threshold for filter

float battery_voltage4 = LOW_VOLTAGE * 1.05; // Battery Voltage of cells 1+2+3+4, initialized above threshold for filter

float battery_current;