Daily Learning! Application of LM35D Temperature Sensor in Arduino

1. Physical Diagram of the Sensor

Physical Diagram 1

Introduction:

LM35 is a temperature sensor produced by National Semiconductor, with an output voltage based on the Celsius scale. LM35 is a widely used temperature sensor. Due to its internal compensation, the output can start from 0°C. LM35 comes in various packaging types. At room temperature, LM35 can achieve an accuracy of ±1/4°C without additional calibration.

The operating voltage is 4-30V, and within this voltage range, the current drawn from the power supply is almost constant (about 50μA), so the chip itself has almost no heat dissipation problem. This small current also makes the chip particularly suitable for certain applications, such as battery-powered scenarios, where the output can be taken from the third pin without needing calibration.

Currently, there are two models of LM35 available. LM35DZ outputs from 0°C to 100°C, while LM35CZ covers -40°C to 110°C with higher accuracy. Both chips have better accuracy than LM35, but they are also slightly more expensive.

2. Specifications

Parameters:

# Calibrated directly at Celsius temperature

# Linear scale coefficient of +10.0mV/°C

# Ensures 0.5°C accuracy (at 25°C)

# Rated temperature range of 0°C to 100°C

# Wide operating voltage range, 4V to 30V

# Low power consumption, less than 60μA

# In still air, self-heating effect is low, less than 0.08°C self-heating

# Non-linearity is only ±1/4°C

# Output impedance is only 0.1Ω with 1mA current

Interface Description:

* Middle: Output signal * Left: Power (VCC) * Right: Ground (GND)

3. Application of this Design

Using a temperature sensor LM35 + Arduino to collect indoor temperature, sending temperature data to the IoT platform via the WIFI module ESP8266-01, and designing an Android APP using MIT App Inventor to display temperature data in real-time.

4. Wiring Diagram

First, we connect the wiring, inserting the LM35 temperature sensor and the configured WIFI module ESP8266-01 onto the breadboard, then connecting them to the Arduino according to the above schematic. The left pin of LM35 is the power pin, connected with a red wire to the 5V power hole of Arduino, the rightmost pin is the ground, connected with a blue wire to the GND hole of Arduino, and the middle pin is the temperature data output, which we connect to the analog signal port 0 (A0). The VCC of the WIFI module ESP8266-01 is connected to the 3.3V power hole of Arduino, GND is connected to the GND hole of Arduino, T connects to X, and X connects to T, as shown in the connection diagram.

5. APP Design

Using MIT App Inventor to design an Android APP.

Menu page design

Data calling (partial modules, block programming)

Debugging data

Example code: Arduino side code, app’s AIA original file, and APK installation file

Download method: Reply “Download”

Note: Next time will write about the configuration method of WIFI module ESP8266-01 and the usage of the IoT platform.