Electronic Thermometer LM35

The electronic thermometer schematic features the LM35DZ temperature sensor. Various types of LM35 integrated circuits exist, but the LM35DZ was selected for this project due to its affordability and availability. This sensor operates within a temperature range of 0°C to 100°C, providing a linear output where the voltage increases by 10 mV for each degree Celsius change. However, the circuit is designed to measure temperatures only between +10°C and +39°C. The middle pin (pin 2) of the LM35DZ is connected to pin 5 of the LM3914 integrated circuit. This configuration allows the LM3914 to control the number of LEDs illuminated on the bar graph display based on the analog signal received from the sensor. A 2.2 microfarad tantalum capacitor is connected between pins 2 and 3 of the LM3914. Additionally, resistors used in the circuit are rated with a tolerance of 1%.

The LM35DZ temperature sensor is an analog device that outputs a voltage proportional to the temperature in degrees Celsius. Its linear response simplifies the conversion of temperature readings into voltage signals suitable for further processing. The choice of the LM35DZ over other variants is primarily due to its cost-effectiveness and ease of accessibility, making it an ideal choice for budget-conscious projects.

The LM3914 is a bar graph/LED dot display driver that interprets the analog voltage output from the LM35DZ. It translates this voltage into a corresponding number of illuminated LEDs, providing a visual representation of the temperature. The connection of the LM35DZ’s output to pin 5 of the LM3914 is crucial, as it allows the IC to read the varying voltage levels and activate the appropriate number of LEDs on the display.

The use of a 2.2 microfarad tantalum capacitor between pins 2 and 3 of the LM3914 serves to stabilize the voltage levels and filter out any noise that might interfere with the sensor's readings. This capacitor helps to ensure that the output remains smooth and reliable, enhancing the accuracy of the temperature display.

Resistors in the circuit, specified with a 1% tolerance, contribute to the overall precision of the circuit. This level of tolerance is important in applications where accurate temperature readings are essential, as it minimizes deviations in the expected performance of the circuit.

Overall, the design of this electronic thermometer circuit effectively combines the LM35DZ sensor and the LM3914 display driver to create a straightforward yet effective temperature measurement system, suitable for various applications where temperature monitoring is required.As shown in the schematic, temperature sensor of our electronic thermometer is LM35DZ. There are some kinds of LM35 IC, since it is cheap and easy to find we used LM35DZ in our project. It measures from 0?C to 100?C with a very linear output graph.For one degree change, it increases its output 10mV. On the Electronic Thermometer Schematic other hand, this circuit measures temperature values only between +10?C and +39?C.

2 numbered (middle) pin of the sensor is connected to the 5 numbered pins of LM3914 ICs. So every IC determines how many leds of bargraph will bright due to the analog signal received from the sensor. 2.2 microfarad tantal capacitors are connected between the 2 and 3 numbered pins of LM3914. Resistors in the circuit have %1 tolerance values. . 🔗 External reference