LM335 Temperature Sensor🌡️

The LM335 is a precision temperature sensor IC that produces a linear voltage output proportional to absolute temperature. With a slope of 10 mV/°C (10 mV/K), it simplifies accurate temperature measurement across a wide range and interfaces easily with ADCs, Arduino, Raspberry Pi (via external ADC), and other microcontroller-based systems.
LM335 Temperature Sensor IC – Linear 10 mV/°C output

Why Choose LM335? ✅

Ideal for engineers and hobbyists, the LM335 combines wide operating range, low output impedance, and low current consumption, making it perfect for electronics components projects, sensor modules, and embedded designs.

Key Features ⚙️

• Temperature Range:
  1. Operating: -40°C to +100°C
  2. Calibrated: 0°C to +100°C
  3. Full range: -55°C to +150°C
• Output Voltage: 10 mV/°C linear slope (10 mV/K)
• Factory Calibration: Accurate output over the specified range; supports user trim for tighter accuracy
• Accuracy: Typically ±1°C at +25°C, and ±2°C over -40°C to +100°C
• Supply Voltage: 2.4 V to 30 V DC
• Output Configuration: Low impedance, linear output; direct interface to ADCs and microcontrollers
• Low Output Impedance: Drives long cables with minimal signal degradation
• Low Quiescent Current: Suitable for battery-powered and portable designs

Typical Applications 🔧

• Temperature measurement in environmental monitoring, industrial control, and automotive systems
• Temperature compensation for analog circuits, oscillators, and precision sensor modules
• Portable devices and handheld instruments thanks to low power consumption

Technical Notes for Designers 🧠

• Bias current: Operates with a constant current source; typical bias range 400 µA to 5 mA (1–2 mA is common)
• Nominal output: ~2.9815 V at 25°C (298.15 K × 10 mV/K)
• Series resistor sizing: For a simple bias from a fixed supply, choose R ≈ (VCC − VOUT) / IBIAS. Example at 5 V and 1.5 mA: R ≈ (5 − 3.0) / 0.0015 ≈ 1.33 kΩ
• Calibration: Optional trim (e.g., with a potentiometer in series/parallel) can reduce absolute error
• Decoupling: Add a small capacitor (e.g., 100 nF) near the sensor for noise immunity, especially with long leads

Integration with Arduino and Raspberry Pi 🤖

The LM335’s voltage output connects directly to an Arduino analog input. For Raspberry Pi, use an external ADC (e.g., MCP3008, ADS1115) to digitize the analog signal.

Wiring Overview 🔌

• Bias: Use a resistor from VCC to the LM335’s Vout pin to set the operating current (e.g., ~1.3 kΩ at 5 V for ~1.5 mA)

• Connections:

  • LM335 Vout → Arduino A0 (or ADC input)
  • LM335 GND → System GND
  • Resistor from VCC (e.g., 5 V) → LM335 Vout

• Optional: Add a 100 nF capacitor from Vout to GND near the sensor

Arduino Example Circuit and Code 🧪

Below is a minimal example for reading the LM335 with an Arduino (assuming a 5 V board and default 10-bit ADC reference):

 // LM335 to Arduino example (5 V reference) // Wiring: VCC --[~1.3kΩ]-- LM335 Vout -- A0, LM335 GND -- GNDconst int lm335Pin = A0;  // LM335 output connected to A0void setup() {   Serial.begin(9600);     // Initialize serial communication }void loop() {   int sensorValue = analogRead(lm335Pin);        // 10-bit ADC: 0..1023   float voltage = sensorValue * (5.0 / 1023.0);  // Convert ADC code to voltage (5 V Arduino)  // LM335 output: 10 mV/K. Temperature (°C) = (Vout / 0.01) - 273.15   float temperatureC = (voltage / 0.01) - 273.15;  Serial.print("Temperature: ");   Serial.print(temperatureC, 2);   Serial.println(" °C");  delay(1000); } 

How It Works 💡

The LM335 outputs a voltage proportional to absolute temperature. The code converts the ADC reading to voltage, then to Kelvin using the 10 mV/K slope, and finally to °C by subtracting 273.15. If you use a different ADC reference (e.g., 3.3 V microcontroller), update the conversion factor accordingly. For tighter accuracy, calibrate at a known temperature and apply an offset or scale factor in code.

Compatibility and SEO Highlights 🔎

• Works with Arduino, Raspberry Pi (via external ADC modules), ESP8266/ESP32, and other microcontroller platforms
• Ideal for electronics components kits, sensor modules, and lab instrumentation
• Designed for precise voltage-based temperature sensing in embedded systems

Notes and Best Practices 📌

• Keep sensor leads short or use shielded cable for noisy environments
• Ensure a stable voltage reference for the ADC to maximize measurement repeatability
• For extended ranges or high precision, consider a two-point calibration