Integrated temperature sensors are currently used in many household appliances. Their large functionality allows them to be used in a variety of devices that are designed to accurately measure temperature. In addition, working in conjunction with a dedicated computer environment, through the graphical user interface we have the ability to change the settings of the system and observe the impact of these changes on the operation of the system and its components. Working with the STEVAL-IFS003V1 evaluation system, we have the opportunity to learn the principle of operation of integrated temperature sensors and observe their communication with other systems.
STEVAL-IFS003V1 Evaluation Board
The STEVAL-IFS003V1 temperature measurement set is an evaluation board manufactured by STMicroelectronics.
Fig. 1. STEVAL-IFS003V1 evaluation board
This system can be powered from an external power source or via USB connected to the PC. The choice of the power supply method is determined by means of a switch. Its main components are as follows:
- Microcontroller ST72F651AR6T1 – The “core” of the entire evaluation board STEVAL-IFS003V1 is a microprocessor integrated circuit with 32 kB HDflash memory with read and write protection.
Fig. 2. ST72F651AR6TI microcontroller with its connections
- Temperature sensors STDS75 and STLM75:
STDS75 is a high-precision integrated circuit of a thermometer operating on a 9-bit sigma-delta converter, whose measurement resolution can be extended to 12 bits. Parameters of this sensor, they are very similar to the STLM75 parameters. On the signal output line OS of the TS2 sensor, a buzzer was connected, which is activated when the set temperature exceeds certain threshold and the voltage is applied to the gate of the Q2 transistor via the OS signal output. It has found it’s application in electronic and computer equipment as well as industrial line controllers. With this sensor it is possible to measure temperature in the range from -55° C to + 125° C (-67° F to + 257° F) and the measurement accuracy is ± 3° C and in the range -25° C to + 100° C accuracy reaches ± 2° C, however the typical accuracy for this sensor is ± 0.5° C.
Fig. 3. STDS75DS2F temperature sensor in the SO-8 housing
STLM75 is a sensor that works and is compatible with the I2C bus. The STLM75 sensor is able to take measurements between -55° C and + 125° C (-67° F to + 257° F). Its accuracy in the whole range of temperature measurement (-55° C to 125° C) is ± 3° C, while in the range -25° C to +100° C the accuracy reaches ± 2° C. The STLM75 voltage range varies from 2,7V to 5,5V. STLM75 is factory-calibrated and does not require external components to measure temperature.
Fig. 4. STLM75M2F temperature sensor in the TSSOP-8 housing
- 5V BLDC fan – The BLDC fan, which is a part of the evaluation system is controlled by the PWM (Pulse Width Modulation) fill factor. Thanks to this solution it is possible to change the rotational speed of the fan depending on the measured temperature value.
- Flash memory (NAND type),
- LCD display.
STEVAL-IFS003V1 – Schematic of internal construction
Schematic of the evaluation board STEVAL-IFS003V1 is shown below:
Fig. 5. STEVAL-IFS003V1 evaluation board schematic
STEVAL-IFS003V1 – Presentation and description of individual components of the system
Fig. 6. Description of individual components of STEVAL-IFS003V1.
Components shown in the Fig. 6. are as follows:
- 1. LCD graphic display,
- 2. Power selection switch,
- 3. External Power Supply connector,
- 4. ST72F651AR6T1 microcontroller,
- 5. Flash memory (NAND type),
- 6. TS1/TS2 address selection switches,
- 7. USB connector,
- 8. Temperature sensor TS1 in the SO-8 housing,
- 9. Temperature sensor TS2 in the TSSOP-8 housing,
- 10. AC Buzzer,
- 11. BLDC fan.
Schematic Source: UM0452 User manual
