System overview

UM1479

20/28

Doc ID 022381 Rev 1

2.1

Hardware design description

Figure 17.

Block diagram

The SW4 is used to connect and disconnect the 3 V coin cell to/from the system. Battery

connection is needed for the data logging stage. For the pre-data/event logging and post

data/event logging stage, power is supplied by the RFID reader and the battery is not

needed in the system.

The SW2 switch is used to check if any of the data is logged in the EEPROM or not.

Below are the steps to follow:

1.

After the data/event logging stage, slide SW4 to the downward position and then back

to the upward position, i.e. power-on reset the system.

2.

Press switch SW2.

3.

If any of the sensors have logged the data inside the EEPROM, the LED D1 blinks on

the data logger board.

4.

Logged data can be read using the RFID reader.

2.1.1

Temperature sensor for temperature data logging

The STTS751 temperature sensor is used in this application. This is a digital temperature

In the case of Event Logger mode:

Temperature thresholds are set for maximum and minimum temperature limits using the GUI

and RFID reader. When the measured temperature is outside these limits the value is

logged inside the EEPROM along with the date, hour and minute of logging.

In the case of Data Logger mode:

The temperature value is measured every second and is recorded inside the memory along

with a time stamp.