Telaire T67 Series Installation and operating instructions

T67xx CO2

Sensor Module

OVERVIEW

The purpose of this document is to outline the required interface design and communication protocol for the

T67xx CO2Sensor modules. The intended audience is any developer who wishes to query the sensor for

information utilizing either the I2C, PWM or UART interfaces.

All information about the performance of the sensor can be found on the Telaire website. Please refer to the

spec sheets found at www.telaire.com for the latest specications.

Amphenol

Advanced Sensors

Application Note

TABLE OF CONTENTS

OVERVIEW ....................................................................................................................................................................1

INSTALLATION AND MOUNTING.................................................................................................................................3

Design Considerations ..................................................................................................................................................3

Installation .....................................................................................................................................................................3

ESD Precautions ...........................................................................................................................................................3

OPERATION DETAILS...................................................................................................................................................3

ABC LOGIC™ ...............................................................................................................................................................3

ENVIRONMENTAL ........................................................................................................................................................4

ABSOLUTE MAXIMUM RATINGS.................................................................................................................................4

Power-On Sequence.....................................................................................................................................................4

Power Supply Requirements.........................................................................................................................................4

Evaluation / Demonstration Kits....................................................................................................................................4

Safety ............................................................................................................................................................................4

Disclaimer......................................................................................................................................................................4

Safety While In Use.......................................................................................................................................................4

MATERIAL CONTENTS.................................................................................................................................................5

INTERFACE CONNECTOR AND OPTIONS ..................................................................................................................5

UART & 1 HZ PWM.......................................................................................................................................................6

I2C & 25 KHZ PWM.......................................................................................................................................................7

PWM OUTPUTS............................................................................................................................................................9

COMMUNICATION – MODBUS PROTOCOL .............................................................................................................12

UART (RS232/RS485) .................................................................................................................................................12

I2C...............................................................................................................................................................................12

I2C Timing Considerations ..........................................................................................................................................12

COMMAND SUMMARY ..............................................................................................................................................13

Firmware Version.........................................................................................................................................................14

Status ..........................................................................................................................................................................15

GAS PPM ....................................................................................................................................................................17

RESET ........................................................................................................................................................................18

START SINGLE POINT CALIBRATION .......................................................................................................................19

CHANGE SLAVE ADDRESS........................................................................................................................................21

ABC LOGIC™ ENABLE / DISABLE ............................................................................................................................22

MEASURE ON DEMAND (MOD) .................................................................................................................................23

MEASURE ON DEMAND MODE USING UART..........................................................................................................24

MEASURE ON DEMAND MODE USING I2C..............................................................................................................26

EXAMPLE CODE.........................................................................................................................................................29

Telaire T67xx CO2Sensor Module Application Note | 3

T67XX CO2SENSOR MODULE

INSTALLATION AND MOUNTING

Design Considerations

To maximize the performance of T67xx module, it is important to plan an appropriate location for the

sensor. Airflow and proper exposure to ambient air must be secured for T67xx module to ensure optimal

performance. Inadequate airflow will deteriorate the response time of the sensor. Too high airflow may

cause extra noise on the sensor output. The preferred installation should have more than 1 mm clearance

above the diffusion fitter on top of the sensor and should be in a location not exposed to high airflow or

turbulence around the sensor. Similarly, avoid excessive heat, preferably placing the sensor away from

high heat dissipating components on the PCB.

The sensor is designed for benign environments. The performance and reliability may be compromised in

environments that contain corrosive or caustic gases including but not limited to Ammonia, Chlorine, NOx

and Ozone. Care must be taken to ensure that the sensor is not exposed to these compounds under any

operating condition.

Installation

The T67xx module is a sensitive electronics assembly, so effort should be made to minimize exposure

to excess heat from any type of soldering operation. Excess exposure to heat from installation is known

to create small shift in calibration of the sensor. Although the ABC Logic™ algorithm (where applied)

will correct these minor fluctuations within the first 24 hours of operation, the user should minimize

overexposure to heat when soldering to negate unexpected operation after installation. Typically, an

expose of not more than 10 sec. using a soldering iron set to 750°F (400°C) will minimize the influence of

heat on the measurement of the T67xx module. The use of low temperature solder is also recommended.

It is recommended to handle the sensor by the edges of the PCBA. Extra stress applied to the PCB or the

gold OBA assembly can cause mechanical stress that will create temporary shift in the calibration of the

sensor. Although he ABC Logic™ algorithm will correct for these shifts in the first 24 hours of operation,

extra care in handling will minimize the risk of variations that can be seen out of the box.

ESD Precautions

Precautions should be taken to observe specified limits and prevent damage from electrostatic discharge

or rough handling. Please refer to ANSI/ESD S20. 20-1999 for more information on preventing ESD

damage for more information on proper electronic assembly practices.

OPERATION DETAILS

ABC LOGIC™

Automatic Background Logic, or ABC Logic, is a patented self-calibration technique that is designed to be

used in applications where concentrations will drop to outside ambient conditions (400 ppm) at least one

time (15 minutes) in a 7day period, which is typically seen during unoccupied periods.

*Full accuracy to be achieved utilizing ABC Logic. With ABC Logic enabled, the sensor will typically reach

its operational accuracy after 25 hours of continuous operation at a condition that it was exposed to

ambient reference levels of air at 400 ppm ±10 ppm CO2. Sensor will maintain accuracy specifications with

ABC Logic enabled, given that it is at least one time per 7 days exposed to the reference value and this

reference value is the lowest concentration to which the sensor is exposed.

ABC Logic requires continuous operation of the sensor for increments of at least 4 hours each.

Note: Applies when used in typical residential ambient air. Consult Amphenol Advanced Sensors if other

gases or corrosive agents are part of the application environment.

T67XX CO2SENSOR MODULE

ENVIRONMENTAL

Operating Temperature: -10°C to 60°C (14°F to 140°F) 0 to 95% RH, non-condensing

Storage Temperature: -30°C to 70°C (-22°F to 158°F)

ABSOLUTE MAXIMUM RATINGS

In order to avoid damage to the sensor, the following parameters should never be exceeded at any time

during operation:

Power-On Sequence

The sensor is capable of responding to commands after power-on, but operational accuracy of sensor

won’t happen until 120 sec have elapsed. The sensor will reach full accuracy / warm up after 10 min. of

operation (exception is ‘–R15’ calibration).

Power Supply Requirements

Supply Voltage: +4.5 – 5.5VDC

Average Current*: 25 (20mA typical)

Peak Current*: 200mA (155mA typical)

*Based on values at a nominal 5VDC input

Evaluation / Demonstration Kits

Evaluation kits are available in order to help customers develop their Air Quality application. The kit

includes a sample of the sensor, cable and software that will enable the user to better understand the

performance of the sensor in their intended design. Please contact Telaire for further details or visit the

website at www.telaire.com.

Safety

Disclaimer

Telaire makes no warranty, representation or guarantee regarding the suitability of this product for any

particular application, including safety critical applications. Nor does Telaire assume any liability arising out

of the application or use in any product or circuit. Telaire specifically disclaims all liability without limitation

consequential or incidental damages. No statuary or fitness for particular purpose shall be implied.

WARNING! Before installing the product, review the product data sheet and this application guide.

The product shall be used only within power supply and electrical input and output limits as

specified by the datasheet and application guide. Improper use of the product may result in product

damage and property loss and/or personal injury.

Safety While In Use

Before installing, handling, using, or servicing this product, please consult the data sheet and

application notes. The product shall be used only within power supply and electrical input and output

limits as specified by the datasheet and application guide. Improper use of the product may result in

product damage and property loss and/or personal injury. In use of the product, the customer has sole

Parameter Min (V) Max (V)

Supply Voltage (V+, pin 3) -0.3 7

Ground (V-, pin 4) -0.3 0.3

TX / SDA, RX / SCL (pin 1,2) -0.3 7

MD DIR / PWM (pin 5) -0.3 7

UART/I2C Select (pin 6) -0.3 3

Telaire T67xx CO2Sensor Module Application Note | 5

responsibility for designing and implementing a solution which will ensure safe operation (including review

of appropriate reliability or required redundancy, mitigation of failure modes, and/or meeting appropriate

standards). The customer is responsible for review of any special conditions for use including, but not

limited to, environmental conditions, electrical supply, residual risk, etc.). The sensor is designed for benign

environments. The performance and reliability may be negatively affected in environments that contain

corrosive or caustic gases including but not limited to Ammonia, Chlorine, NOx and Ozone.

MATERIAL CONTENTS

ROHS, REACH and Proposition 65 declaration of conformity are available upon request. Please contact

customer service for more details.

INTERFACE CONNECTOR AND OPTIONS

The six pin through-hole connector on the PCB is where power and IO for the sensor are located, see

Figure 1 below. A four to six pin, 0.1” (2.54mm) header is typically used to connect the sensor to a

controller. There are several different I/O configurations described in the following sections that are

supported by the sensor and are determined by the voltage that is measured on pin 6 of the connector at

startup.

Figure 1 - T67XX Interface Connector

Note: Precautions should be taken to observe specified limits and prevent damage from electrostatic

discharge or rough handling. Please refer to ANSI/ESD S20. 20-1999 for more information on preventing

ESD damage and IPC 610 Rev D for more information on proper electronic assembly practices. In addition

to this, the sensor does not have internal reverse polarity protection. Care should be taken to connect the

sensor to the controller in the correct wiring configuration to avoid damage. Sensor is not designed for hot

swapping.

T67XX CO2SENSOR MODULE

1. TX / SDA

2. TX / SCL

3. V++

4. GND

5. PWM

6. CTRL / TEST

T67XX CO2SENSOR MODULE

UART & 1 HZ PWM

Pin 6 is left unconnected by the user and will therefore be left floating. It will be pulled up by an internal

1MΩresistor. In this condition:

Table 1 – I/O Pin Configuration #1

Pin Description

1UART TX (output from sensor)

2UART Rx (input to sensor)

5PWM output at approximately 1Hz

Figure 2 - Simplified Schematic I/O configuration #1

In this condition, the sensor implements a RS-232 serial interface. The default serial conditions are:

• 19200 Baud

• 1 START bit

• 8 DATA bits

• 1 EVEN PARITY bit

• 1 STOP bit

Telaire T67xx CO2Sensor Module Application Note | 7

T67XX CO2SENSOR MODULE

I2C & 25 KHZ PWM

Pin 6 is grounded by the user. In this condition:

Table 2 - I/O Pin Configuration #2

Pin Description

1UART TX (output from sensor)

2UART Rx (input to sensor)

5PWM output at approximately 1Hz

Figure 3 - Simplified Schematic I/O configuration #2

In this condition, the sensor implements an I2C interface. The default conditions are:

• The sensor only acts as a slave device

• I2C 7-bit addressing is used. The default slave address is 0x15 (21)

• I2C 100kbit/s Standard Mode

Note: There is an internal pull up resistor on pin 1 of the I2C interface. Customer will need to provide an

external pull up resistor on pin 2 with a recommended value of 4.7k. I2C interface can operate at both 3.3V

and 5V logic levels.

T67XX CO2SENSOR MODULE

6.3 UART WITH RS485 TRANSCEVER SUPPORT

Pin 6 is pulled to ground by a resistor between 10kΩand 100kΩ

Table 3 - I/O Pin Configuration #3

Pin Description

1 UART TX (output from sensor)

2 UART Rx (input to sensor)

5Becomes a test input for Telaire and should be left unconnected by the user

6 Becomes an output pin used to control an RS485 transceiver

Figure 4 - Simplified Schematic I/O Configuration #3

The condition described by (3) above is useful if the sensor is used in an RS485 dropped node network

configuration. This network would be supplied by the user. In this condition pin 6 controls the RS-485

transceiver data-direction logic.

Telaire T67xx CO2Sensor Module Application Note | 9

T67XX CO2SENSOR MODULE

PWM OUTPUTS

The T67xx sensor has a selectable Pulse Width Modulation (PWM) output feature on Pin 5, based on the

state of Pin 6 during power on.

The two types of supported PWM operate at ~1Hz and 25 kHz and are scaled to the range of the sensor

as determined by the model. For example, if the model is a T6713-5k, the units PWM output will have 0 to

5000 ppm output range. For the model T6713, the units PWM will have 0 – 2000 ppm output range.

An external pull up resistor to a voltage between 3.3 to 5V is required on the PWM output. Typical value

could be anywhere from 4.7 kOhm to 100 kOhm depending on chosen frequency of the PWM output and

capacitance of the output load.

The slow ~1Hz PWM output option supports legacy application and was developed to communicate with

simple low cost microcontrollers without using complex communication protocols. It allows the user to

measure the duration of the pulse, and correlate this to a CO2measurements. Each PWM cycle has start

sequence including 2 msec of low level followed by 2 msec of high level.

Figure 5 - Details of ~1Hz PWM

In order to convert the pulse to a reading in PPM, the user should use the following equation:

PPM=(t_pulse-2)*2 for 0 – 2000 ppm models

PPM=(t_pulse-2)*5 for 0 – 5000 ppm models

Where:

t_pulse=Measured duration of pulse in msec

PPM=Measured CO2Value

T67XX CO2SENSOR MODULE

Figure 6 - Example of the PWM for -2K model

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