API for the OTP538U IR Temperature Sensor. More...

Detailed Description

ID: otp538u
Name: Analog IR Temperature Sensor
Other Names: Grove IR Temperature Sensor
Category: light
Manufacturer: generic
Connection: analog
Link: http://wiki.seeed.cc/Grove-Infrared_Temperature_Sensor/
Kit: hak

UPM module for the OTP538U IR temperature sensor

This module was tested with the Grove IR non-contact temperature sensor.

The sensor provides 2 analog outputs: one for the thermistor that measures the ambient temperature, and the other for the thermopile that measures the object temperature.

Much of the code depends on analyzing Seeed Studio* examples and the circuit design. As a result, there are several 'magic' numbers derived from their circuit design. These values are used by default.

The tables used came from the "538U VT Table__20_200(v1.3).pdf" and "538RT_table.pdf" datasheets.

These tables assume the object to be measured is 9 cm (3.54 inches) from the sensor.

This sensor will not work at 3.3v on the Edsion or the Galileo 2. It works fine on both systems at 5v. It will work at 3.3v on the Arduino 101 (tested via firmata subplatform on edison).

    // Instantiate a OTP538U on analog pins A0 and A1
    // A0 is used for the Ambient Temperature and A1 is used for the
    // Object temperature.
    upm::OTP538U temps(0, 1, OTP538U_AREF);
    // enable debugging if you would like
    // temps.setDebug(true);
    // Output ambient and object temperatures
    while (shouldRun) {
        try {
            cout << "Ambient temp: " << std::fixed << setprecision(2) << temps.ambientTemperature()
                 << " C, Object temp: " << temps.objectTemperature() << " C" << endl;
        } catch (std::out_of_range& e) {
            cerr << "Temperature(s) are out of range: " << e.what() << endl;
        }
        cout << endl;
        upm_delay(1);
    }

Public Member Functions
	OTP538U (int pinA, int pinO, float aref=5.0)

	~OTP538U ()

float	ambientTemperature ()

float	objectTemperature ()

void	setVoltageOffset (float vOffset)

void	setOutputResistence (int outResistance)

void	setVRef (float vref)

void	setDebug (bool enable)

Protected Attributes
otp538u_context	m_otp538u

Constructor & Destructor Documentation

OTP538U	(	int	pinA,
		int	pinO,
		float	aref = `5.0`
	)

OTP538U constructor

Parameters

pinA	Analog pin to use for the ambient temperature
pinO	Analog pin to use for the object temperature
aref	Analog reference voltage; default is 5.0 V

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~OTP538U ( )

OTP538U destructor

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Member Function Documentation

float ambientTemperature ( )

Gets the ambient temperature in Celsius

Returns: Ambient temperature

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float objectTemperature ( )

Gets the object temperature in Celsius

Returns: Object temperature

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void setVoltageOffset ( float vOffset )

inline

Sets the offset voltage

The Seeed Studio wiki gives an example of calibrating the sensor and calculating the offset voltage to apply. Currently, the default value is set, but you can use the function to set one of your own.

Parameters

vOffset Desired offset voltage

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void setOutputResistence ( int outResistance )

inline

Sets the output resistance value

The Seeed Studio wiki example uses a value of 2,000,000 in one of the equations used to calculate voltage. The value is the resistance of a resistor they use in the output stage of their SIG2 output. This was 'decoded' by looking at the EAGLE* files containing their schematics for this device.

Parameters

outResistance Value of the output resistor; default is 2M Ohm

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void setVRef ( float vref )

inline

Sets the reference voltage of the internal Seeed Studio voltage regulator on the sensor board.

The Seeed Studio wiki example uses a value of 2.5 in one of the equations used to calculate the resistance of the ambient thermistor. The value is the voltage of an internal voltage regulator used on the sensor board. This was 'decoded' by looking at the EAGLE files containing their schematics for this device.

Parameters