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Temperature and relative humidity display with adaptive brightness control

Posted on July 3, 2012 by R-B 9 comments

The objective of this project is to illustrate a technique of implementing adaptive brightness control to seven segment LED displays. 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. For the proof of concept, the technique is applied to construct a digital temperature and relative humidity meter that adapts the brightness of the seven segment LED displays to the surrounding lighting conditions. There are 8 seven segment LED displays used in this project and they are all driven by

Dual 4-digit seven segment LED display with SPI interface

Posted on June 26, 2012 by R-B 2 comments

This project is an extension of my previous MAX7219 based SPI seven segment LED display module. The new display features eight 7-segment displays arranged in two rows of four digits. The on-board MAX7219 driver enables you to easily add eight 7-segment LED displays to your project using only 3 I/O pins of microcontroller. The major advantage of using this board is the time-division multiplexing operations required for continuous refreshing of the display digits are performed by the MAX7219 chip, thereby keeping the microcontroller free for doing other pressing tasks. It is suitable for displaying two variable values simultaneously in a

Serial four digit 7-segment LED display module

Posted on May 7, 2012 by R-B 29 comments

Seven segment LED displays are a very popular mean of displaying numerical information and finds application in front panel display boards of microwave ovens, washers and dryers, digital clocks, frequency counters, and many other gadgets. Compared to the LCD displays, the seven segment LED displays are brighter and provide a far viewing distance and a wide viewing angle. However, the downside is they are resource-hungry. It requires at least 12 I/O pins of a microcontroller to drive a standard 4-digit seven segment LED module. Consequently, their use with low pin-count microcontrollers (such as PIC12F series) is not practically feasible. Here’s

Making a digital capacitance meter using microcontroller

Posted on March 25, 2012 by R-B 42 comments

Capacitors are one of the most common passive electrical components that are extensively used in all kinds of electronic circuits. In this project, we will discuss a technique of building a digital capacitance meter using a PIC microcontroller. This project can measure capacitance values from 1 nF to 99 ?F, with a resolution of 1 nF. The technique is based on measuring the time elapsed when a capacitor is charged to a known voltage through a series resistor. The microcontroller used in this project is PIC16F628A.

A brief overview of Allegro ACS712 current sensor (Part 2)

Posted on January 25, 2012 by R-B 37 comments

In the first part of this discussion, the features of ACS712 device were briefly discussed. Now we will use that theory to implement the ACS712 sensor to make a simple DC current meter. The analog output voltage from the sensor is measured through an ADC channel of the PIC16F1847 microcontroller. A voltage to current conversion equation will be derived and implemented in the firmware of the PIC microcontroller and the actual load current will be displayed on a character LCD.

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