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Category Archives: PIC18F

Using TC74 (Microchip) thermal sensor for temperature measurement

Posted on July 17, 2011 by R-B 26 comments

The TC74 chip is a serially accessible, digital temperature sensor from Microchip Technology that acquires and converts temperature information from its onboard solid-state sensor with a resolution of 1°C. The temperature is available as an 8-bit digital word stored in its internal temperature register, which is accessible through a 2-wire I2C compatible serial bus. This tutorial describes how to use the TC74 sensor with a PIC microcontroller to measure the surrounding temperature.

LM386 based stereo audio amplifier with digital volume control

Posted on June 26, 2011 by R-B 65 comments

Due to its simplicity (requires minimum external components) and high availability, LM386 is very popular among hobbyists for use in low-voltage audio amplification applications. Most of the time a potentiometer is used at the input side of LM386 to provide a volume control in the output speaker. The potentiometer does not control the gain of the amplifier itself, but it creates a voltage divider network at the input, which in fact controls the fraction of the audio signal that is fed to the amplifier. This project is about a stereo audio amplifier using two LM386 ICs with digital volume control for both

Humidity and temperature measurements with Sensirion’s SHT1x/SHT7x sensors (Part 2)

Posted on May 28, 2011 by R-B 11 comments

In Part 1 of this tutorial, we discussed about Sensirion’s SHT1x and SHT7x series of humidity sensors, their interface specifications, the communication protocol used for transferring data in and out of the sensor, and the equations to convert their digital outputs to actual physical quantities. These sensors are capable of measuring temperature along with relative humidity and provide outputs in fully-calibrated digital words. We will now see how a PIC microcontroller can be programmed to communicate with these sensors, read the temperature and relative humidity data, and display the information on a character LCD.

Humidity and temperature measurements with Sensirion’s SHT1x/SHT7x sensors (Part 1)

Posted on May 28, 2011 by R-B 5 comments

Temperature and relative humidity are two very important ambient parameters that are directly related to human comfort. Sometimes, you may be able to bear higher temperatures, if there is a lower relative humidity, such as in hot and dry desert-like environment. However, being in a humid place with not very high temperature may make you feel like melting. This is because if there is high relative humidity, sweat from our body will evaporate less into the air and we feel much hotter than the actual temperature. Humidifiers and dehumidifiers help to keep indoor humidity at a comfortable level. Today we will

Lab 15: Scrolling text message on an LED dot-matrix display

Posted on May 21, 2011 by R-B 160 comments

In Lab 12, we learned about the basic structure of a monochrome (single color) LED dot matrix and its interface with a microcontroller to display static characters and symbols. Today’s lab is its continuation, and we will be discussing on displaying a scrolling text message on a 16×8 LED dot matrix. The microcontroller used is again the same PIC18F2550 from StartUSB for PIC board. The 16 columns of the LED matrix are driven individually by two shift registers (74HC595), whereas the eight combined rows are driven by the decoded outputs from a decade counter (CD4017). In Lab 12, columns were

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