November | 2010 | Embedded Lab

Monthly Archives: November 2010

Lab 7: PIC Timers and Counters (Part 1)

Posted on November 21, 2010 by R-B 56 comments

Description PIC microcontrollers are equipped with one or more precision timing systems known as Timers. They can be used to perform a variety of time precision functions, such as generating events at specific times, measuring the duration of an event, keeping date and time record, counting events, etc. The main component of a timer module is a free running binary counter that increments for each incoming pulse. Since it runs independently, it can count pulses concurrently with the main program execution. A PIC16F688 microcontroller has two built-in hardware timer modules: Timer0 and Timer1. Today’s lab lesson will explore the functionality

A multifunction digital meter using Atmega128

Posted on November 20, 2010 by R-B 3 comments

This is a multifunction bench test instrument built using an Atmega128 microcontroller and incorporate a lot of functions like voltmeter, ammeter, logic analyzer, frequency generator, frequency counter and also provides regulated DC power supply. This device is interfaced with a Windows PC to display the measurements. The PC software is developed in VB 6. The function generator is based on a MAX038 IC that can provide sine, triangle or square wave, with adjustable duty cycle, from about 1 Hz to > 20 MHz.

AVR digital clock with white seven segment LED display

Posted on November 19, 2010 by R-B One comment

This is a digital clock project based on an ATtiny26 microcontroller, displaying time on four seven segment LEDs. The seven segment LEDs glow bright white and are multiplexed through PORTB pins, whereas the segments are driven by PORTA pins. The time is normally shown in hh.mm format but it can be switched to display mm.ss too. The time setting can be done with two push button switches.

Low power temperature data logger using PIC18F27J53

Posted on November 18, 2010 by R-B Leave a comment

Most of the microcontroller based data loggers use external EEPROM chips for storing the measurement values. This increases the cost, power consumptionm, and the size of the circuit board. Instead, why don’t we choose a microcontroller with a larger flash memory and use it for storing the data. Actually, a data logger’s firmware is not very big in size. So, the remaining flash memory can be used to store the data from realtime measurements. This project is based on the same concept and uses a PIC18F27J53 microcontroller that has 128K programmable flash memory. The PIC18F27J53 family microcontrollers are low power

Calibrating a thermistor for temperature measurements

Posted on November 17, 2010 by R-B Leave a comment

A thermistor is a passive device that changes its resistance with temperature. If the temperature-resistance characteristic is known, it can be used as a temperature sensor by measuring the resistance, or more precisely, the voltage across it. Thermistors are classified in to two types: NTC (negative temperature coefficient) and PTC (positive temperature coefficient). A NTC thermistor decreases its resistance while the temperature rises, and a PTC does the opposite. Although the datasheet of a thermistor describes the temperature-resistance relationship, the measurement based on that is not very accurate. Therefore, you may need to calibrate it against a more accurate sensor.

« Older Entries Recent Entries »