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Connecting multiple tact switches on a single input pin of a microcontroller

Posted on November 18, 2011 by R-B 6 comments

Normally one tact switch requires one digital input pin of a microcontroller. Some designs implement keypad style multiplexing to get multiple switches on fewer inputs. However, there exist other techniques that allow you to connect many switches on a single input pin of a microcontroller. This tutorial demonstrates one such technique as applied to PIC12F683 microcontroller. In this example, there are four LEDs and four tact switches connected to the PIC12F683 microcontroller. While each LED is controlled through an individual I/O pin, the four switches are connected to one ADC input pin of the PIC12F683 microcontroller.

Revised version of LM35 based digital temperature meter

Posted on November 6, 2011 by R-B 39 comments

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

Lab 19: Play musical notes

Posted on November 3, 2011 by R-B 22 comments

We have discussed in the past experiments how to use a PIC microcontroller to do a variety of things from flashing an LED to driving a motor, etc. Today, we will see how to play notes of a song with a PIC microcontroller. Musical notes are simply sound waves of particular frequencies. If the frequency of a note is known correctly, a microcontroller can be programmed to play the note by generating a square wave (of the same frequency) signal at one of its I/O pins. The signal must be fed to a speaker to listen to the sound. Here,

How to use mikroElektronika’s GLCD bitmap editor tool to convert a BMP image in to a data array

Posted on October 24, 2011 by R-B 6 comments

This tutorial describes how to use the mikroElektronika’s GLCD bitmap editor tool to convert a monochromatic bit map (BMP) image file into a data array so that it could be displayed on a graphics LCD using a microcontroller. The GLCD bitmap editor tool is embedded into mikroElektronika’s compilers. It can generate a code equivalent of a BMP image, which can be easily inserted into the microcontroller’s source program.

Low cost temperature data logger using PIC and Processing

Posted on October 16, 2011 by R-B 35 comments

This project describes an easy and inexpensive way of adding a digital thermometer and data logging feature to a PC. It involves a PIC microcontroller that gets the surrounding temperature information from the Microchip MCP9701 sensor, and sends it to a PC through an USB-UART interface. The USB port of the PC is also used to power the device. The open-source Processing programming platform is used to develop a PC application that displays the temperature in a graphics window on the computer screen. The PC application also records the temperature samples plus date and time stamps on an ASCII file.

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