OTP538U Class Reference

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

Detailed Description

• ID: otp538u
• Name: OTP538U IR Temperature Sensor
• Other Names: Grove IR Temperature Sensor
• Category: light
• Manufacturer: generic
• Connection: analog
• 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.

  // 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 = new upm::OTP538U(0, 1, OTP538U_AREF);
  
  // Output ambient and object temperatures
  while (shouldRun)
    {
      cout << "Ambient temp: " << std::fixed << setprecision(2) 
           << temps->ambientTemperature() 
           << " C, Object temp: " << temps->objectTemperature() 
           << " C" << endl;
      
      sleep(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)

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

~OTP538U

(

)

OTP538U destructor

Member Function Documentation

float ambientTemperature

(

)

Gets the ambient temperature in Celsius

Returns

Ambient temperature

float objectTemperature

(

)

Gets the object temperature in Celsius

Returns

Object temperature

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

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

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

vref	Reference voltage of the internal sensor; default is 2.5 V

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

• /iotdk/jenkins/workspace/upm-doc-stable/src/otp538u/otp538u.h
• /iotdk/jenkins/workspace/upm-doc-stable/src/otp538u/otp538u.cxx