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A brief overview of Allegro ACS712 current sensor (Part 1)

Posted on January 25, 2012 by R-B 18 comments

Sensing and controlling current flow is a fundamental requirement in a wide variety of applications including, over-current protection circuits, battery chargers, switching mode power supplies, digital watt meters, programmable current sources, etc. One of the simplest techniques of sensing current is to place a small value resistance (also known as Shunt resistor) in between the load and the ground and measure the voltage drop across it, which in fact, is proportional to the current flowing through it. Whereas this technique is easy and straightforward to implement, it may not be very precise because the value of the shunt resistor slightly

Building a digital light meter with a calibrated LDR

Posted on January 13, 2012 by R-B 28 comments

Measurement of light intensity is a prime necessity in several occasions. The diversity of such needs make their way to various branches of physics and engineering as well as in media. For instance, in engineering, such kinds of measurements are needed to design optimum lighting conditions of a room. In photography, light intensity measurements ensure good quality pictures by determining the right exposure. Wiring a phototransistor or a light-dependent-resistor (LDR) with an analogue LED voltmeter chip like the LM3914 or even to a microcontroller and displaying the ADC values is a pretty simple technique of measuring light intensity. The bad

Measurement of temperature and relative humidity using DHT11 sensor and PIC microcontroller

Posted on January 10, 2012 by R-B 140 comments

Measurement and control of temperature and relative humidity finds applications in numerous areas. These days devices are available which have both temperature and humidity sensors with signal conditioning, ADC, calibration and communication interface all built inside them. The use of such smart sensors greatly simplify the design and reduces the overall cost. We discussed in past about Humidity and temperature measurements with Sensirion’s SHT1x/SHT7x sensors. These sensors are capable of measuring both temperature and relative humidity and provide fully calibrated digital outputs. While SHT1x/SHT7x are very accurate sensors, they are still expensive for hobbyists use. This articles discusses the DHT11 sensor

Embedded Lab projects built by Kevin Murphy

Posted on January 8, 2012 by R-B Leave a comment

Kevin Murphy from New Boston, Michigan is a regular reader of Embedded Lab. He adapted our digital timer project to fulfill his need of a programmable timer switch for his darkroom. Here are some pictures that he has sent us showing how his assembled PCB of this project look like. He also received a PCB for the 18-pin PIC16F board from us last week. The following pictures shows his assembled breadboard module for PIC16F628. Thank you, Kevin for sharing these pictures with us.

Lab 20: Interfacing a KS0108 based Graphics LCD (Part 2)

Posted on January 5, 2012 by R-B 7 comments

In the first part of this tutorial, we discussed about Winstar’s WDG0151-TMI GLCD module, which is a 128×64 pixel monochromatic display built with KS0108B and KS0107B compatible display controllers. The module was interfaced to a PIC16F887 microcontroller and a test program was written in C to demonstrate how to implement the KS0108 instruction set in the firmware of PIC to activate display pixels on the screen. We wrote our subroutine programs that would turn the GLCD on, move the display location to a specified row and column, and draw a pixel at a given coordinates. You might have realized it

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