17-01-2013, 04:37 PM
A SUITE OF ELECTRONIC CIRCUITS CONSTRUCTION AND SIMULATION USING THE ELECTRONIC WORKBENCH SOFTWARE
A SUITE OF ELECTRONIC CIRCUITS.pdf (Size: 428.24 KB / Downloads: 33)
ABSTRACT
The project deals with the construction and simulation of electronic circuits using the electronic workbench software prior to their implementation in the electronic laboratory. Circuits simulation prior to their implementation provides several benefits such as more accurate design closer to the theoretical estimation, greater flexibility to test the sensitivity of the components to variations in element values, explore circuit concepts and behavior, and provides risk free environment for students learning. The aim of the project was to compare computer simulated circuits with practical circuits constructed in the lab and results commented upon.
INTRODUCTION
The project required the use of Electronic Workbench (EWB) Software for the construction and simulation of electronic circuits. The EWB is a simple to use software and provide a wide scope for circuits simulation and presentation. The aim of the project was to compare simulated results obtained from the EWB with those obtained from practical circuits constructed in the laboratory. Five circuits will be tested in the lab among those that would have been simulated and results compared and commented upon. This piece of work can be applicable in the lab for students during their laboratory work, and it will help them appreciate circuits concepts and behavior. Chapter 1 deals with timer circuits (Astable and monostable). The detailed operation and testing of the circuits were considered. Chapter 2 covers the detailed operation and testing of the operational amplifiers (Inverting, summing and non-inverting). Chapter 3 deals with active filters (Lowpass, highpass and bandpass). The detailed operation, analysis and testing were considered. Chapter 4 deals with counters. Truth tables, implementation and waveforms are shown were necessary.
The 555 Timer 1.0 Introduction The 8-pin 555 timer is one of the most useful integrated circuits (ICs) ever invented. It comes in as a single or dual package and low power CMOS versions exist- IC7555. Popular versions are LM555, LM556, NE555, and NE556. With just a few external components it can be used to build many circuits, not all of them involve timing. The 555 timer is capable of producing accurate time delays or creating oscillations. The timing is control by external components and connections. It is very flexible with operation voltage in the range +4.5 to +15V. You can sink or source about 200mA of current through it. Application includes; precision timing, time delay generation, sequential timing, pulse generation, etc. 1.1 Types of 555 Timers Astable - producing a square wave Monostable - producing a single pulse when triggered Bistable - a simple memory which can be set and reset Buffer - an inverting buffer (Schmitt trigger)
Circuit operation
With the output high (+VCC), the capacitor C1 is charged by current flowing
through R1 and R2. The threshold and trigger inputs share a common mode.
They monitor the capacitor voltage and when it reaches 3
2 Vcc (threshold
voltage) the output becomes low and the discharge pin is connected to 0V.
The capacitor now discharges with current flowing through R2 into the
discharge pin. When the voltage falls to 3
1 VCC (trigger voltage) the output
becomes high again and the discharge pin is disconnected, allowing the
capacitor to start charging again. This cycle repeats continuously unless the
reset input is connected to 0V which forces the output low. The reset input
can override all other inputs and can be used to initiate a new timing cycle.
Introduction
The operational amplifier is simply a high gain, direct-coupled amplifier. It
is usually designed to amplify signals extending over a wide frequency range
and is normally used with external feedback networks.
There are certain ‘ideal properties’ of op amps toward which their design is
directed. These properties are never realized in practice, but the assumption
of such idealness allows rapid preliminary analysis of feedback circuits
involving these amplifiers. The idealized amplifier properties which are
usually assumed are: