Microchip Technology

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  • Multiple Zone Temperature Monitoring

  • Created: Jul 27, 2016

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Temperature is the degree of heat present in an object, which is a comparative measurement of either hot or cold. There are situations that require a constant degree of temperature. In these cases, a temperature sensor needs to monitor the degree of temperature. The TCN75A is a 2-wire serial temperature sensor that can convert temperatures between -40°C and +125°C to a digital word. It has a register setting that allows temperature resolution measurement of 0.5°C to 0.0625°C. The sensor is compatible with standard 2-wire, I2C serial interface that allows up to eight devices to be controlled in a single serial bus. These features make the TCN75A ideal for low-cost, multi-zone temperature monitoring applications.

The design is a multi zone temperature monitoring circuit. It has eight temperature sensors that can be placed in different locations. This is done by using selectable addressing that is implemented by pulling the three address (A0, A1, and A2) to either VDD or Ground, this provides a total of eight devices that can be addressed on the same two-wire serial bus. It uses an I2C serial interface to communicate to the microcontroller. The circuit is powered by a 3.3V supply voltage. The temperature sensor can be set to specific limits that sends signal through ALERT pin if it goes beyond the set limits. The pin RB0 is connected to the LCD and has an isolation resistor (R4) from the ALERT connection of the temperature sensors. R2 and R3 are pull up resistors for the I2C bus, while R1 is a weak pull-up when RB0 is configured as an input waiting for ALERT interrupt of the temperature data. The data that are collected from the ALERT in each temperature sensor is displayed on the LCD. The circuit has a buzzer when one of the sensors goes beyond the specific limit.

The temperature monitoring can be used in situations where constant temperature level is critical like operating rooms in hospitals, refrigerators and servers. The circuit can be integrated in applications that require multi-zone temperature monitoring like workstations, office electronics, and appliances at home.



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