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Stephan Mühl
2023-03-22 12:15:18 +01:00
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commit adb5102869
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203
lib/LightResistor/LightDependentResistor.cpp Normal file
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/*
* \brief Get light intensity value (Lux & FootCandles) from Light dependent Resistor (implementation)
*
* \author Quentin Comte-Gaz <quentin@comte-gaz.com>
* \date 30 January 2023
* \license MIT License (contact me if too restrictive)
* \copyright Copyright (c) 2023 Quentin Comte-Gaz
* \version 1.4
*/
#include "LightDependentResistor.h"
LightDependentResistor::LightDependentResistor(int pin, unsigned long other_resistor, ePhotoCellKind kind, unsigned int adc_resolution_bits, unsigned int smoothing_history_size) :
_pin (pin),
_other_resistor (other_resistor),
_mult_value(32017200),
_pow_value(1.5832),
_photocell_on_ground (true),
_adc_resolution_bits(adc_resolution_bits),
_smoothing_sum(0.0f),
_smoothing_history_size(smoothing_history_size),
_smoothing_history_next(0),
_smoothing_history_values(new float[smoothing_history_size])
{
switch (kind)
{
case GL5516:
_mult_value = 29634400;
_pow_value = 1.6689;
break;
case GL5537_1:
_mult_value = 32435800;
_pow_value = 1.4899;
break;
case GL5537_2:
_mult_value = 2801820;
_pow_value = 1.1772;
break;
case GL5539:
_mult_value = 208510000;
_pow_value = 1.4850;
break;
case GL5549:
_mult_value = 44682100;
_pow_value = 1.2750;
break;
case GL5528:
default:
_mult_value = 32017200;
_pow_value = 1.5832;
}
for (unsigned int i = 0 ; i < _smoothing_history_size ; i++)
{
// We initialize the values as impossible value (lux can't be negative)
_smoothing_history_values[i] = -1.0f;
}
}
LightDependentResistor::LightDependentResistor(int pin, unsigned long other_resistor, float mult_value, float pow_value, unsigned int adc_resolution_bits, unsigned int smoothing_history_size) :
_pin (pin),
_other_resistor (other_resistor),
_mult_value (mult_value),
_pow_value (pow_value),
_photocell_on_ground (true),
_adc_resolution_bits(adc_resolution_bits),
_smoothing_sum(0.0f),
_smoothing_history_size(smoothing_history_size),
_smoothing_history_next(0),
_smoothing_history_values(new float[smoothing_history_size])
{
for (unsigned int i = 0 ; i < _smoothing_history_size ; i++)
{
// We initialize the values as impossible value (lux can't be negative)
_smoothing_history_values[i] = -1.0f;
}
}
LightDependentResistor::~LightDependentResistor()
{
// De-allocate the table at the end of the use of the class
delete[] _smoothing_history_values;
}
void LightDependentResistor::updatePhotocellParameters(float mult_value, float pow_value)
{
_mult_value = mult_value;
_pow_value = pow_value;
}
float LightDependentResistor::luxToFootCandles(float intensity_in_lux)
{
return intensity_in_lux/10.764;
}
float LightDependentResistor::footCandlesToLux(float intensity_in_footcandles)
{
return 10.764*intensity_in_footcandles;
}
void LightDependentResistor::setPhotocellPositionOnGround(bool on_ground)
{
_photocell_on_ground = on_ground;
}
int LightDependentResistor::getCurrentRawAnalogValue() const
{
// Analog resolution setter is not handled on all boards (not compatible boards: MEGA, ESP8266, Uno)
#if !defined(__AVR_ATmega1280__) && !defined(__AVR_ATmega2560__) && !defined(ESP8266) && !defined(__AVR_ATmega328P__) && !defined(__AVR_ATmega168__)
analogReadResolution(_adc_resolution_bits);
#endif
return analogRead(_pin);
}
float LightDependentResistor::rawAnalogValueToLux(int raw_analog_value) const
{
unsigned long photocell_resistor;
if (pow(2, _adc_resolution_bits) == raw_analog_value)
{
raw_analog_value--;
}
float ratio = ((float)pow(2, _adc_resolution_bits) / (float)raw_analog_value) - 1;
if (_photocell_on_ground)
{
photocell_resistor = _other_resistor / ratio;
}
else
{
photocell_resistor = _other_resistor * ratio;
}
return _mult_value / (float)pow(photocell_resistor, _pow_value);
}
float LightDependentResistor::getCurrentLux() const
{
return rawAnalogValueToLux(getCurrentRawAnalogValue());
}
float LightDependentResistor::getCurrentFootCandles() const
{
return luxToFootCandles(getCurrentLux());
}
float LightDependentResistor::getSmoothedLux()
{
float sumResult = 0;
if (_smoothing_history_size == 0)
{
// Smoothing disabled, return current value.
sumResult = getCurrentLux();
}
else
{
if (_smoothing_history_values[_smoothing_history_next] < -0.1f)
{
// Smoothing enabled but not all values are filled yet
// (Let's fill one more)
_smoothing_history_values[_smoothing_history_next] = getCurrentLux();
_smoothing_sum += _smoothing_history_values[_smoothing_history_next];
if (_smoothing_history_next < _smoothing_history_size - 1)
{
// Still not all buffers filled
_smoothing_history_next++;
sumResult = _smoothing_sum / _smoothing_history_next;
}
else
{
// All buffers filled now, start regular operation
_smoothing_history_next = 0;
sumResult = _smoothing_sum / _smoothing_history_size;
}
}
else
{
// Smoothing enabled and buffer filled previously.
// => Regular operation from now on:
// Replace previous value by the new one (from buffer and sum)
_smoothing_sum -= _smoothing_history_values[_smoothing_history_next];
_smoothing_history_values[_smoothing_history_next] = getCurrentLux();
_smoothing_sum += _smoothing_history_values[_smoothing_history_next];
// Update next value tu acquire
_smoothing_history_next = (_smoothing_history_next < _smoothing_history_size - 1) ? _smoothing_history_next + 1 : 0;
sumResult = _smoothing_sum / _smoothing_history_size;
}
}
return sumResult;
}
float LightDependentResistor::getSmoothedFootCandles()
{
return luxToFootCandles(getSmoothedLux());
}

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lib/LightResistor/LightDependentResistor.h Normal file
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/*
* \brief Get light intensity value (Lux & FootCandles) from Light dependent Resistor (LDR) a.k.a. photocell or photoresistor
*
* This library is easily usable with most GL55xx photoresistors (at ~25°C).
*
* It is also possible to use it with any other photocell (with the right parameters).
* If you use this library with other photocells, please send me the parameters in
* order to add them in the list.
*
* Schematics:
* ^
* _____ ___/___
* 5V |---|_____|----|__/____|--| GND
* or Other /
* 3.3V Resistor Photocell
*
* Note: By default, the photocell must be on the ground.
* It is possible to exchange the position of the photocell and the other resistor
* but you will have to call \p setPhotocellPositionOnGround(false).
*
* \author Quentin Comte-Gaz <quentin@comte-gaz.com>
* \date 30 January 2023
* \license MIT License (contact me if too restrictive)
* \copyright Copyright (c) 2023 Quentin Comte-Gaz
* \version 1.4
*/
#ifndef LightDependentResistor_h
#define LightDependentResistor_h
#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif
class LightDependentResistor
{
public:
/*!
* \enum ePhotoCellKind Photocell component
*/
enum ePhotoCellKind {
GL5516,
GL5528,
GL5537_1,
GL5537_2,
GL5539,
GL5549
};
/*!
* \brief LightDependentResistor Initialize the light intensity getter class
*
* \param pin (int) Analog pin connected to the voltage divider
* \param other_resistor (unsigned long) Resistor used for the voltage divider
* \param kind (ePhotoCellKind) Used photocell
* \param adc_resolution_bits (unsigned int, optional, default: 10) Number of resolution bits for the ADC pin (more information here: https://www.arduino.cc/reference/en/language/functions/analog-io/analogread/)
* \param smoothing_history_size (unsigned int, optional, default: 10) Max number of raw values used for \f getSmoothedLux or \f getSmoothedFootCandles
*/
LightDependentResistor(int pin, unsigned long other_resistor, ePhotoCellKind kind = GL5528, unsigned int adc_resolution_bits = 10, unsigned int smoothing_history_size = 10);
/*!
* \brief LightDependentResistor Initialize the light intensity getter class
*
* Even thought some photocells are already defined, it is possible to
* define your own photocell.
* The relation between the photocell resistor and the lux intensity can be
* approximated to I[lux]=mult_value/(R[Ω]^pow_value).
*
* Example for GL5528 photocell:
* 1) Find curve Resistor->Lux intensity: http://cdn.sparkfun.com/datasheets/Sensors/LightImaging/SEN-09088.pdf
* 2) Get 2 points from the datasheet log curve: log(55000[Ω])->log(1[lux]) and log(3000[Ω])->log(100[lux])
* 3) Convert those 2 point into a "log linear curve" (with Excel for example): log(R[Ω]) = -0.6316 * log(I[lux]) + 4.7404 (linear)
* 4) Solve the equation to get I[lux]=mult_value/(R[Ω]^pow_value) approximation (with wolframalpha for example): I[lux] ~= 32017200/R[Ω]^1.5832
* https://www.wolframalpha.com/input/?i=log10(x)%3D-0.6316*log10(y)%2B4.7404
* 5) You just found the 2 parameters: mult_value=32017200 and pow_value=1.5832
*
* \param pin (int) Analog pin connected to the voltage divider
* \param other_resistor (unsigned long) Resistor used for the voltage divider
* \param mult_value (float) Multiplication parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
* \param pow_value (float) Power parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
* \param adc_resolution_bits (unsigned int, optional, default: 10) Number of resolution bits for the ADC pin (more information here: https://www.arduino.cc/reference/en/language/functions/analog-io/analogread/)
* \param smoothing_history_size (unsigned int, optional, default: 10) Max number of raw values used for \f getSmoothedLux or \f getSmoothedFootCandles
*/
LightDependentResistor(int pin, unsigned long other_resistor, float mult_value, float pow_value, unsigned int adc_resolution_bits = 10, unsigned int smoothing_history_size = 10);
~LightDependentResistor();
/*!
* \brief getCurrentLux Get light intensity (in lux) from the photocell
*
* \return (float) Light intensity (in lux)
*/
float getCurrentLux() const;
/*!
* \brief getCurrentFootCandles Get light intensity (in footcandles) from the photocell
*
* \return (float) Light intensity (in footcandles)
*/
float getCurrentFootCandles() const;
/*!
* \brief getCurrentRawAnalogValue Read light intensity from the photocell, and provide the sensor raw analogic value (not a really readable value)
*
* \return (int) Light intensity (in sensor raw analogic value), not a really readable value, prefer \f getCurrentLux or \f getCurrentFootCandles
*/
int getCurrentRawAnalogValue() const;
/*!
* \brief rawAnalogValueToLux Convert raw value from photocell sensor into lux
*
* This function is only needed if the sensor MUST NOT be handled by this library...
* Else, it is better to directly use \f getCurrentLux that will read sensor value and convert it into lux.
*
* \param raw_value (int) Analog value of the photocell sensor (WARNING: This value must be with the same adc resolution as the one in the constructor)
*
* \return (float) Light intensity (in lux)
*/
float rawAnalogValueToLux(int raw_analog_value) const;
/*!
* \brief luxToFootCandles Get footcandles from lux intensity
*
* \param intensity_in_lux (float) Intensity in lux
*
* \return Footcandles retrieved from \p intensity_in_lux
*/
static float luxToFootCandles(float intensity_in_lux);
/*!
* \brief footCandlesToLux Get Lux intensity from footcandles
*
* \param intensity_in_footcandles (float) Footcandles
*
* \return Intensity in lux retrieved from \p intensity_in_footcandles
*/
static float footCandlesToLux(float intensity_in_footcandles);
/*!
* \brief setPhotocellPositionOnGround Configure the photocell as connected to +5V/3.3V or GND
*
* \param on_ground (bool) True if the photocell is connected to GND, else false
*
* True: ^
* _____ ___/___
* 5V |---|_____|----|__/____|--| GND
* or Other /
* 3.3V Resistor Photocell
*
* False: ^
* _____ ___/___
* GND |---|_____|----|__/____|--| 5V
* Other / or
* Resistor Photocell 3.3V
*/
void setPhotocellPositionOnGround(bool on_ground);
/*!
* \brief updatePhotocellParameters Redefine the photocell parameters
*
* \param mult_value (float) Multiplication parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
* \param pow_value (float) Power parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
*/
void updatePhotocellParameters(float mult_value, float pow_value);
/*!
* \brief getSmoothedLux Read light intensity (in lux) from the photocell, apply linear smoothing using the number of historic values specified with the constructor.
*
* \return (float) Light intensity (in lux) after applying linear smoothing
*/
float getSmoothedLux();
/*!
* \brief getCurrentFootCandles Read light intensity from the photocell, apply linear smoothing using the number of historic values specified with the constructor, convert to footcandles.
*
* \return (float) Light intensity (in footcandles) after applying linear smoothing
*/
float getSmoothedFootCandles();
private:
int _pin; //!< Analog pin connected to the voltage divider
unsigned long _other_resistor; //!< Resistor used for the voltage divider
float _mult_value; //!< Multiplication parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
float _pow_value; //!< Power parameter in "I[lux]=mult_value/(R[Ω]^pow_value)" expression
bool _photocell_on_ground; //!< Photocell is connected to +5V/3.3V (false) or GND (true) ?
unsigned int _adc_resolution_bits; //!< Number of resolution bits for the ADC pin
float _smoothing_sum; //!< (smoothing only) Current sum of valid values of \v _smoothing_history_values
unsigned int _smoothing_history_size; //!< (smoothing only) Size of the table of values
unsigned int _smoothing_history_next; //!< (smoothing only) Next value to get/replace
float* _smoothing_history_values; //!< (smoothing only) All valid values (in lux) in a table of \v _smoothing_history_size values maximum (oldest value will be replaced by a new one if table is full)
};
#endif //LightDependentResistor_h