TrH Meter is a DIY microcontroller-based indoor thermometer plus hygrometer that displays temperature (F/C) and relative humidity on 4 seven segment LED displays which adjust their brightness level according to the surrounding illumination. The displays are 1 inch big, emits bright yellow color, and are readable from more than 50 ft away. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display. The DHT11 sensor is used to measure temperature and relative humidity. The microcontroller used in this project is PIC16F688, and it runs at 4 MHz internal clock. A separate display driver chip (MAX7219) is used to control and refresh the display data on the seven segment LEDs. A 3-position slide switch controls power ON/OFF and Fahrenheit (F) or Celsius (C) scale select for temperature display. You can now preorder the project kit for a discounted price of $25 on Tindie. You will receive a preprogrammed PIC16F688 microcontroller in the kit.
TrH Meter project kit is now available for preorder on Tindie - [Link]
This project is about building a microcontroller-based digital room thermometer plus hygrometer that displays temperature and relative humidity on 4 large (1 inch) seven segment LED displays which adjust their brightness level according to the surrounding illumination. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display. An inexpensive DHT11 sensor is used to measure temperature and relative humidity. The microcontroller used in this project is PIC16F688, and it runs at 4 MHz clock generated from its internal source. A separate display driver chip (MAX7219) is used to control and refresh the display data on the seven segment LEDs.
TrH Meter: A DIY indoor thermometer plus hygrometer with adaptive brightness - [Link]
This is a revised version of my LM35 based digital thermometer project that I posted last year. Although it is one of the simplest projects, it is very popular among newbies who are just starting to learn microcontrollers. There was a little flaw in the original project as pointed by some readers. I was using a 1.2 V reference for A/D conversion with PIC16F688 microcontroller. However, the PIC16F688 datasheet says Vref should be equal to or higher than 2.2 V to ensure 1 LSB accuracy of A/D conversion. Here, I am rewriting the same project but this time I am using a MCP1525 IC to generate a precise 2.5 V reference for A/D conversion. This will improve the accuracy of temperature measurements.
Revised version of LM35 based digital temperature meter - [Link]
The term UART (Universal Asynchronous Receiver Transmitter) is the technical term for the good old serial port found on most MCUs. The term USART similarly refers to a serial port capable of handling both synchronous and asynchronous operation. Over the past few years, Microchip has been integrating an updated serial port into many of their MCUs known as the Enhanced Universal Synchronous Asynchronous Receiver Transmitter or EUSART.
The main feature of EUSART is the ability to auto-detect the baud rate of received signals. An example of of a chip featuring EUSART is the PIC16F688, which is the subject of a Microchip App Note covering the use of EUSART.
A practical illustration of the EUSART in action is this sample project from ENMCU using the PIC18F2455 to detect the baud rate of a serial character received and display the speed on an attached LCD.
Using the EUSART – [Link]
This project describes in detail how to use a LM35 temperature sensor to measure the surrounding temperature and display on a LCD screen by interfacing with a PIC microcontrolller. The LM35 sensor gives an analog output voltage that is proportional to the temperature. The output from the sensor is converted to a 10-bit digital number by the internal ADC of PIC16F688 micro. This project provides every details of software and hardware design involved.
Measuring temperature using LM35 Sensor – [Link]
Room temperature plays a vital role in determining human thermal comfort. This digital thermometer is designed to measure room temperature and display it on a LCD screen in both Celsius and Fahrenheit scales. A PIC16F688 microchip is used as the main controller that reads temperature from DS1820, a 3-pin digital temperature sensor from Dallas semiconductors (now Maxim). The sensor is designed to measure temperature ranging from -55 to +125 °C in 0.5 °C increments.
Digital Room Thermometer - [Link]