Connect an LM75 temperature sensor to an ESP32

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In this example we will connect an LM75 temperature sensor to an ESP32 module, in this case our favourite Wemos LOLIN32. Lets look at some technical information about the LM75

The LM75 temperature sensor includes a delta-sigma analog-to-digital converter, and a digital overtemperature detector. The host can query the LM75 through its I²C interface to read temperature at any time.

The open-drain overtemperature output (OS) sinks current when the programmable temperature limit is exceeded. The OS output operates in either of two modes, comparator or interrupt.

The host controls the temperature at which the alarm is asserted (TOS) and the hysteresis temperature below which the alarm condition is not valid (THYST). Also, the LM75’s TOS and THYST registers can be read by the host. The address of the LM75 is set with three pins to allow multiple devices to work on the same bus.

Power-up is in comparator mode, with defaults of TOS = +80°C and THYST = +75°C. The 3.0V to 5.5V supply voltage range, low supply current, and I²C interface make the LM75 ideal for many applications in thermal management and protection.

 

Features

SO (SOP) and µMAX® (µSOP) Packages
I²C Bus Interface
Separate Open-Drain OS Output Operates as Interrupt or Comparator/Thermostat Input
Register Readback Capability
Power-Up Defaults Permit Stand-Alone Operation as a Thermostat
3.0V to 5.5V Supply Voltage
Low Operating Supply Current 250µA (typ), 1mA (max)
4µA (typ) Shutdown Mode Minimizes Power Consumption
Up to Eight LM75s Can Be Connected to a Single Bus

Layout

A simple module to connect being an I2C device which is 3.3v powered, this layout shows a module connected to a Wemos Lolin32

ESP32-and-lm75 example
ESP32-and-lm75 example

 

Code

The following library is required, downlaod and install into the Arduino IDE – https://github.com/jlz3008/lm75

This is pretty much the default example

#define VERSION "1.1"
 
#include <inttypes.h>
#include <Wire.h>
 
#include <lm75.h>
 
TempI2C_LM75 termo = TempI2C_LM75(0x48,TempI2C_LM75::nine_bits);
 
void setup()
{
Serial.begin(9600);
Serial.println("Start");
Serial.print("Actual temp ");
Serial.print(termo.getTemp());
Serial.println(" oC");
delay(2000);
}
 
void loop()
{
Serial.print(termo.getTemp());
Serial.println(" oC");
delay(5000);
}

 

 

 

Links

LM75 CJMCU-75 temperature sensor high speed I2C interface high precision development board module

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