A thermistor analog device. More...

#include <grmcdorman/device/ThermistorSensor.h>

Inheritance diagram for grmcdorman::device::ThermistorSensor:

Public Member Functions
	ThermistorSensor (float thermalIndex, float t1Kelvin)
	Construct a new ThermistorSensor object. More...

DynamicJsonDocument	as_json () const override
	Get the values, as a JSON document. More...

virtual String	get_status () const
	Get a status report. More...

Public Member Functions inherited from grmcdorman::device::AbstractAnalog
	AbstractAnalog (const __FlashStringHelper device_name, const __FlashStringHelper device_identifier, float defaultScale=1.0f, float defaultOffset=0.0f, bool invert=false)
	Construct a new Basic Analog object. More...

void	setup () override
	Setup the device. More...

void	loop () override
	Main loop. More...

bool	publish (DynamicJsonDocument &json) const override
	Publish the value and attributes. More...

float	get_last_reading () const
	Last computed reading. More...

float	raw_value () const
	Last raw value (no scale or offset applied). More...

float	get_current_average () const
	Get the last average reading. More...

Public Member Functions inherited from grmcdorman::device::Device
	Device (const __FlashStringHelper device_name, const __FlashStringHelper device_identifier)
	Construct a new Device object. More...

virtual	~Device ()
	Destroy the Device object.

const __FlashStringHelper *	name () const
	Get the device name; used for UI names and IDs. More...

virtual const __FlashStringHelper *	identifier () const
	Get the device identifier. More...

virtual void	set_defaults ()
	Set defaults, if necessary. More...

virtual void	set_devices (const std::vector< Device * > &list)
	For devices that support it, add devices to manage. More...

const definition_list_t &	get_definitions () const
	Get the definitions list. More...

const ::grmcdorman::SettingInterface::settings_list_t &	get_settings () const
	Get the settings list. More...

bool	is_enabled () const
	Get whether this device is enabled. More...

void	set_enabled (bool state)
	Set whether this device is enabled. More...

void	set (const String &setting, const String &value)
	If possible, set a setting's value. More...

String	get (const String &setting) const
	Get a setting value, as a string. More...

virtual bool	get_is_published () const
	Get whether the device readings have been published. More...

void	set_is_published ()
	Set the device as having published readings. More...

void	clear_is_published ()
	Set the device as not having published readings.

Protected Member Functions
virtual float	transform_raw_reading (int reading) override
	Transform the raw reading to a temperature. More...

Protected Member Functions inherited from grmcdorman::device::Device
void	initialize (definition_list_t &&definition_list, ::grmcdorman::SettingInterface::settings_list_t &&setting_list)
	Initialize the definition and setting lists. More...

Protected Attributes
float	inverse_thermal_index
	The inverse of thermal index of the thermistor.

float	inverse_t1
	The inverse of the T1 temperature of the thermistor.

NoteSetting	title
	Device tab title.

InfoSettingHtml	device_status
	Last update.

Protected Attributes inherited from grmcdorman::device::AbstractAnalog
FloatSetting	scale
	Offset.

FloatSetting	offset
	Scaling.

ToggleSetting	invertReading
	Whether to invert the reading.

UnsignedIntegerSetting	readInterval
	How often to request a reading.

uint32_t	last_read_millis = 0
	Timestamp of last read.

Accumulator< float, 5 >	sensor_reading
	Reading.

Protected Attributes inherited from grmcdorman::device::Device
ToggleSetting	enabled
	Whether this device is enabled.

Additional Inherited Members
Public Types inherited from grmcdorman::device::Device
typedef std::vector< const Definition * >	definition_list_t
	The type containing a list of Definition objects.

Static Public Member Functions inherited from grmcdorman::device::Device
static void	set_system_identifiers (const __FlashStringHelper *firmware_name_value, const String &system_identifier_value=String())
	Set the system identifier values. More...

static const __FlashStringHelper *	get_firmware_name ()
	Get the firmware prefix. More...

static const String &	get_system_identifier ()
	Get the system identifier. More...

Static Public Attributes inherited from grmcdorman::device::Device
static constexpr int	D0 = 16
	D0 is GPIO16, HIGH at boot, not suitable for most usages.

static constexpr int	D1 = 5
	D1 is GPIO5; often used as SCL.

static constexpr int	D2 = 4
	D2 is GPIO4; often used as SDA.

static constexpr int	D3 = 0
	D3 is GPIO0; pulled up; connected to FLASH button; not for input.

static constexpr int	D4 = 2
	D4 is GPIO2; pulled up; HIGH at boot; on-board LED; not for input.

static constexpr int	D5 = 14
	D5 is GPIO14; SPI (SCLK)

static constexpr int	D6 = 12
	D6 is GPIO12; SPI (MISO)

static constexpr int	D7 = 13
	D7 is GPIO13; SPI (MOSI)

static constexpr int	D8 = 15
	D8 is GPIO15; pulled to GND; SPI (CS); not recommended.

static const ExclusiveOptionSetting::names_list_t	data_line_names { FPSTR("D1"), FPSTR("D2"), FPSTR("D3"), FPSTR("D5"), FPSTR("D6"), FPSTR("D7")}
	Names for each configurable data line; see `settingsMap`.

Static Protected Member Functions inherited from grmcdorman::device::Device
static int	index_to_dataline (int index)
	Convert a data line index to a ESP data line. More...

static int	dataline_to_index (int dataLine)
	Convert a data line to an index. More...

Static Protected Attributes inherited from grmcdorman::device::AbstractAnalog
constexpr static uint32_t	statusReadInterval = (30 / 5) * 1000
	Default read interval. Chosen such that there should be 5 readings per 30 seconds.

Static Protected Attributes inherited from grmcdorman::device::Device
static const int	settingsMap [6]
	The set of data lines usable for communication. More...

Detailed Description

A thermistor analog device.

This device reads A0 and transforms the reading according to the standard thermistor properties to get a reading in degrees Celcius.

Scaling can be applied to the reading after conversion to Celcius; this can be used to transform to other scales, such as Fahrenheit, or to correct inaccuracies. To convert to Fahrenheit, set the scale to 1.8 (9/5) and the offset to +32.

The calculations make the following assumptions:

The ADC maximum value, 1023, corresponds to the +V supplied to the thermistor; i.e. the reference voltage and ADC voltage source are the same.
The resistor in series with the thermistor has a value close to the thermistor's resistance.
The thermistor is connected between the GND and the resistor.

In other words, if your ESP8266 reads 1023 or 1024 for +3.3V, and your thermistor has a nominal resistance of 10K ohms at about 20 Celcius, then connect a 10K resistor in series with the thermistor between +3.3V and GND, and connect A0 to the junction of the thermistor and the resistor. In rough ASCII art:

 [3.3V]------[10K resistor]------[thermistor]------[GND]
                             |
                            A0

If your ADC does not have a maximum of 3.3V, then use a voltage divider to supply the ADC maximum - probably 1V - to the resistor.

Thermistors have three parameters:

Thermal index (or Beta)
Calibration temperature, or T1, in Kelvin
Nominal resistance at T1, R.

For example, I have a thermistor with B of 3950, R of 10k, and T1 of 25C, or (273.15+25)=298.15K.

Only the thermal index (beta) and T1 value are needed.

When publishing to MQTT, only the last reading is published, not the average reading over the interval.

Constructor & Destructor Documentation

◆ ThermistorSensor()

grmcdorman::device::ThermistorSensor::ThermistorSensor	(	float	thermalIndex,
		float	t1Kelvin
	)

Construct a new ThermistorSensor object.

Parameters

thermalIndex	The thermal index of the thermistor, e.g. 3950.
t1Kelvin	The T1 temperature of the thermistor in Kelvin, e.g. 298.15 (25C).

Member Function Documentation

◆ as_json()

DynamicJsonDocument grmcdorman::device::ThermistorSensor::as_json ( ) const

overridevirtual

Get the values, as a JSON document.

The structure is identical to the document created inside publish.

Returns: DynamicJsonDocument

Reimplemented from grmcdorman::device::AbstractAnalog.

◆ get_status()

String grmcdorman::device::ThermistorSensor::get_status ( ) const

virtual

Get a status report.

This is also used for the device_status info message, with the exception of various disabled states.

Returns: String containing status report.

Reimplemented from grmcdorman::device::Device.

◆ transform_raw_reading()

float grmcdorman::device::ThermistorSensor::transform_raw_reading ( int reading )

overrideprotectedvirtual

Transform the raw reading to a temperature.

The parameters from the constructor, and the assumptions about the wiring, are used to compute the temperature.

Parameters

reading Raw reading.

Returns: Temperature, in degrees C.

Implements grmcdorman::device::AbstractAnalog.

The documentation for this class was generated from the following files:

grmcdorman/device/ThermistorSensor.h
ThermistorSensor.cpp

Public Member Functions

Protected Member Functions

Protected Attributes