Published October 22, 2016

Electric Box Supervisor

I would like to use the Analog Coprocessor Pioneer Kit to create the supervisor for the electric box for outdoor usage.

BeginnerFull instructions provided8 hours696

Things used in this project

Hardware components

Cypress PSoC Analog Coprocessor Pioneer Kit

Story

INTRODUCTION:

I would like to use Analog Coprocessor Pioneer Kit in order to address the following problem:

Electric boxes are especially used for outdoor applications and because of that sometimes it can be bad for the device. When either temperature or humidity conditions are not optimal then maintaining the box can cause serious damage. Since an electric box is under high voltage any drop of water on “hot” elements can be fatal for them and it is the best way to harm the device inside the box. Moreover it can be also dangerous for an operator who maintains it.

Conditions that are perilous to be considered:

Electric components inside the box work under the both high temperature and humidity conditions.

Outside temperature is low. While maintaining the box by an operator, temperature inside the box is higher.

Well known is a situation where components inside an electric box are being cooled down quite quickly and in fact we can observe occurrence of the “dew point” effect.

The “dew point” can cause appearing of water drops on “hot” elements mentioned earlier. In result it can be a reason to short circuit.

Solution proposal:

1. Temperature and humidity sensors can calculate when the “dew point” effect is possible based on the surrounding conditions.

2. Indication on the front panel if opening the box is safe - for example by using LED signal. (Red - danger do not open / Green - good to operate)

3. When it’s red then an operator is able to use a ambient light sensor as switch (cover the sensor by finger will behave as pressing the button). It will allow him to activate an internally mounted fan and heater to rise temperature and allow to circulate the air faster inside the electric box. In result the “dew point” can be decreased to a level being safe for the device inside.

SCHEMATIC:

I have based my project using the PSoC Analog Coprocessor pioneer kit (CY8KIT-048).

CODE:

Main operation is related to Dew Point calculation. I have used the formula described in one of the application note from Sensirion company www.sensirion.com

RESULT:

Measure the temperature inside box (DieTemp sensor) and outside box (thermistor)

Measure humidity inside the box

Calculate the dew point occurrence if the temperature inside box will drop to outside level ( door open by operator ).

If unsafe conditions can occur Red LED is on

If the safe conditions present then Green LED is on

In the project I have also used the ALS sensor to work as a button (decided to do it because it provide a good galvanic isolation). Covering the ALS sensor will allow to turn on the AC fan and heater inside the box and allow to remove the unsafe conditions. Operator can activate it only when the danger conditions are present.

Code

Electric_Supervisor

/******************************************************************************
* Project Name      : Electric Box Supervisor 
* Version           : 1.0
* Device Used       : CY8C4A45LQI-L483
* Software Used     : PSoC Creator 4.0 update 1
* Compiler Used     : ARM GCC 4.9.3 
* Related Hardware  : CY8CKIT-048 PSoC Analog Coprocessor Pioneer Kit 
*******************************************************************************/

#include "project.h"
#include "math.h"

// 
#define ADC_CHANNEL_VREF			    (0u)
#define ADC_CHANNEL_VTH				    (1u)
#define ADC_CHANNEL_ALS                 (2u)
#define ADC_CHANNEL_DIE				    (3u)

#define FILTER_COEFFICIENT_TEMPERATURE	(32u)

#define CAPACITANCE_AT_55_RH            (1800)

/* Sensitivity numerator and denominator indicate sensitivity of the sensor */
#define SENSITIVITY_NUMERATOR           (31)
#define SENSITIVITY_DENOMINATOR         (100)
/* Value of reference capacitor.  Note that this value includes the pin capacitance
    and the physical 180pF reference capacitor */
#define CREF                            (1930)
/* Offset Capacitance */
#define COFFSET                         (150)
/* This is raw count equivalent to trace capacitance */
#define OFFSETCOUNT                     (1536)
#define BUFFERSIZE                      (8)
#define READ_WRITE_BOUNDARY             (0)
/* Nominal humidity 55% */
#define NOMINAL_HUMIDITY                (550)
#define HUMIDITY_0_PERCENT              (0)
#define HUMIDITY_100_PERCENT            (1000)
#define HUMIDITY_50                     (500)   

#define FILTER_COEFFICIENT_ALS	        (10)

/* Constants for photodiode current calculation */
/* Scale Factor = (VREF / (2048 * 220K)) * 10^9 nA = 2.6633 
   As the TIA produces a negative voltage, the scale factor is made 
   negative */
#define ALS_CURRENT_SCALE_FACTOR_NUMERATOR		(-26633)
#define ALS_CURRENT_SCALE_FACTOR_DENOMINATOR	(10000)

/* Constants for ambient light calculation */
/* Scale Factor = 10000Lx / 3000nA = 3.333 */
#define ALS_LIGHT_SCALE_FACTOR_NUMERATOR		(3333)
#define ALS_LIGHT_SCALE_FACTOR_DENOMINATOR		(1000)


#define LED_ON						    (0u)
#define LED_OFF						    (1u)

// Variables to hold the the ADC readings 
int16 adcResultVREF, adcResultVTH, adcResultDie,adcResultALS;
    
//Filter input and output variables for Vref and Vth measurements 

int16 filterOutputVref=0;
int16 filterOutputVth=0;
  
// Variables for temperature readings

int16 thermistorResistance, temperature, correction;
int32 temp_out_box,temp_in_box;
    
// Variables for relative moisture readings

uint16 humidityRawCounts;	/* Raw count from CapSense Component for the humidity sensor */
uint16 capacitance;			/* Capacitance of the humidity sensor */
uint16 humidity;			/* Measured humidity */
uint16 rawCountsRefCap;     /* Raw count from CapSense Component for the Reference capacitor */

// Variables for ALS readings
int16 alsCurrent;
uint16 illuminance;
int16 alsCurrent;			/* Ambient light sensor current output */
uint16 illuminance; 		/* Ambient light illuminance */	
uint16 illuminance2;
// Variables for main processing

float H,RH,DewPoint_Temp;

int16 filterInput;
int32 filterOutput = 0;


__inline uint16 CalculateCapacitance(uint16 rawCounts, uint16 refSensorCounts);
__inline uint16 CalculateHumidity(uint16 capacitance);

int main(void)
{
    CyGlobalIntEnable; /* Enable global interrupts. */

    
    ADC_Start();
    CSD_Start();
    VrefBuffer_Start();
    PVref_Start();
    PVref_Enable();
    Opamp_TIA_Start();
    
    for(;;)
    {
        
        ADC_StartConvert(); 
        ADC_IsEndConversion(ADC_WAIT_FOR_RESULT); 
        adcResultVREF = ADC_GetResult16(ADC_CHANNEL_VREF);
        adcResultVTH = ADC_GetResult16(ADC_CHANNEL_VTH);
        adcResultDie = ADC_GetResult16(ADC_CHANNEL_DIE);
        adcResultALS= ADC_GetResult16(ADC_CHANNEL_ALS);
     
        
         //TEMPERATURE CALCULATIONS
        
        /* Low pass filter the measured ADC counts of Vref */            
        filterOutputVref = (adcResultVREF + (FILTER_COEFFICIENT_TEMPERATURE - 1) * filterOutputVref) / FILTER_COEFFICIENT_TEMPERATURE;
        /* Low pass filter the measured ADC counts of Vth */         
        filterOutputVth = (adcResultVTH + (FILTER_COEFFICIENT_TEMPERATURE - 1) * filterOutputVth) / FILTER_COEFFICIENT_TEMPERATURE;
        /* Calculate thermistor resistance */
        thermistorResistance = Thermistor_GetResistance(filterOutputVref, filterOutputVth);           
       
        /* Calculate temperature in degree Celsius using the Component API */
        temperature = Thermistor_GetTemperature(thermistorResistance);
        temp_out_box=temperature*0.01;  // External temperature out side the electic box
        
        /* Calculate temperature in degree Celsius using the Component API */
        
        correction=(1.2/1.024)*adcResultDie; // Reference voltage used is 1.2V while for the DieTemp sensor reference voltage is 1.024V
        temp_in_box = DieTemp_CountsTo_Celsius(correction);// Internal temperature inside the electic box

        //LIGHTING CALCULATIONS
                        
        /* Low pass filter the ADC result */
		filterInput = adcResultALS;
    	filterOutput = (filterInput + (FILTER_COEFFICIENT_ALS - 1)*filterOutput)/FILTER_COEFFICIENT_ALS;
    	/* Calculate the photodiode current */
		alsCurrent = (filterOutput * ALS_CURRENT_SCALE_FACTOR_NUMERATOR)/ALS_CURRENT_SCALE_FACTOR_DENOMINATOR; 
		/* If the calculated current is negative, limit it to zero */
		
         if(alsCurrent < 0)	alsCurrent = 0;
        
        illuminance = (alsCurrent * ALS_LIGHT_SCALE_FACTOR_NUMERATOR)/ALS_LIGHT_SCALE_FACTOR_DENOMINATOR;	
        
        CyDelay(500);
        
        filterInput = adcResultALS;
    	filterOutput = (filterInput + (FILTER_COEFFICIENT_ALS - 1)*filterOutput)/FILTER_COEFFICIENT_ALS;
    	/* Calculate the photodiode current */
		alsCurrent = (filterOutput * ALS_CURRENT_SCALE_FACTOR_NUMERATOR)/ALS_CURRENT_SCALE_FACTOR_DENOMINATOR; 
		/* If the calculated current is negative, limit it to zero */
		
         if(alsCurrent < 0)	alsCurrent = 0;
 
        illuminance2 = (alsCurrent * ALS_LIGHT_SCALE_FACTOR_NUMERATOR)/ALS_LIGHT_SCALE_FACTOR_DENOMINATOR;	
           
          if(!(CSD_IsBusy()))
        {       
           humidityRawCounts = CSD_BUTTON0_SNS0_RAW0_VALUE;
           rawCountsRefCap = CSD_BUTTON0_SNS1_RAW0_VALUE;
           /* Convert raw counts to capacitance */
           capacitance = CalculateCapacitance(humidityRawCounts, rawCountsRefCap);
           /*Calculate humidity */
           humidity = CalculateHumidity(capacitance);  
           RH=humidity*0.1;
           CSD_ScanAllWidgets();
        }
        
  // Main calcualations
        
        H=(log10(RH)-2)/0.4343 + (17.62*temp_out_box)/(243.12+temp_out_box);
        DewPoint_Temp= 243.12*H/(17.62-H); // temperature when dew point can be reached
          
          if(illuminance2<illuminance)
        {
            Pin_FAN_Heater_Write(LED_ON);
        }
     
        if (temp_out_box <= DewPoint_Temp ) {
            Pin_LED_Green_Write(LED_OFF);
            Pin_LED_Red_Write(LED_ON);
        }
            else
        {
             Pin_LED_Green_Write(LED_ON);
              Pin_LED_Red_Write(LED_OFF);
            Pin_FAN_Heater_Write(LED_OFF);
        }
         
        
    }
}
__inline uint16 CalculateCapacitance(uint16 rawCounts, uint16 refsensorCounts)
{
    return (uint16)((float)(rawCounts - OFFSETCOUNT) * (CREF - COFFSET) / (float)(refsensorCounts - OFFSETCOUNT));
}

__inline uint16 CalculateHumidity(uint16 capacitance)
{
    int16 humidity;
    int16 delta;
    /* Find capacitance difference from nominal capacitance at 55% RH */
    delta = capacitance - CAPACITANCE_AT_55_RH;
    /* Calculate humidity from capacitance difference and sensor sensitivity */
    humidity = ((delta * SENSITIVITY_DENOMINATOR) / SENSITIVITY_NUMERATOR) + NOMINAL_HUMIDITY;
    /* If humidity is less than zero, limit it to 0; If humidity is greater than 1000 (100%), limit to 1000 */
    humidity = (humidity < HUMIDITY_0_PERCENT) ? HUMIDITY_0_PERCENT : (humidity > HUMIDITY_100_PERCENT) ? HUMIDITY_100_PERCENT : humidity;
    /* Return Humidity value */
    return humidity;
}

/* [] END OF FILE */

Credits

Jacek Pieczaba

6 projects • 7 followers

Hardware design engineer;Technology enthusiast;