login
You are not logged in.
search:
AMSER logo



Title: DC Power Control Using a NE555 Timer and a Power MOS FET SWF
Url: http://www.matec.org/forums/_attachments/lil_six/cac.swf
Creator: Palmer, John
Publisher: Maricopa Advanced Technology Education Center (MATEC)
Description: This Learning Invention Lab from MATEC describes DC power control using a NE555 timer and a power MOS FET. The initial presentation will show the internal function blocks of the NE 555 timer. Each of the internal blocks will be described in relation to the whole timer block diagram. This will include the comparators, flip-flop, inverter, discharge transistor, reset transistor and the three 5000 ohm resistors in the internal divider network. A basic general circuit for the timer will then be used to explain the operation of the timer as an astable oscillator with formulas for the time high and time low of the output. Combining these times will yield the period of the output from which the frequency can be determined. A second very similar circuit will show how to vary the frequency with a potentiometer connected as a rheostat. If a dual trace oscilloscope is available to the student, a trace of the trigger input and the resulting output can be shown. The student will notice that in the second circuit that both the frequency and the duty cycle change as the rheostat is adjusted. In each of the previous circuits the student needs to become familiar with the operation of the internal blocks of the timer and how they change as the timer goes through a complete cycle. This included the charge and discharge path for the current in the timing capacitor. The student needs to have built up each of the two circuits and at least have access to a scope to watch the input and output voltages change as a function of time. The LEDs on the output will indicate that the circuit is functioning properly. The actual PWM motor control uses diodes (sometimes called steering diodes) to keep the output frequency constant while the output pulse width can be varied from a small fraction of the period to nearly of the full period of the output waveform. The oscilloscope can be used to observe the timing capacitor charge and discharge in relation to the PWM output from pin 3 of the timer. Since the output of the timer is limited to about 15 milliamps, it is used to control a N-channel enhancement mode FET which has higher current handling capacity. The FET is used as an electronic switch which conducts when its gate voltage is HIGH and is OFF when its gate voltage is LOW. The longer the gate is HIGH the faster the motor turns because power is applied for a longer time during each timer cycle.
LC Classification: Bibliography. Library science. Information resources (General) -- Subject bibliography -- Education -- Special topics, A-Z -- Engineering education
Education -- Special aspects of education -- Types of education -- Vocational education (General) -- Special topics, A-Z -- Curriculum
Technology -- Electrical engineering. Electronics. Nuclear engineering -- Electrical engineering. Electronics. Nuclear engineering -- Distribution or transmission of electric power -- Systems -- Direct-current systems
Technology -- Electrical engineering. Electronics. Nuclear engineering -- Electrical engineering. Electronics. Nuclear engineering -- Dynamoelectric machinery and auxiliaries -- Dynamoelectric machinery -- Direct-current machinery -- Special direct-current machinery -- Direct-current motors
Technology -- Electrical engineering. Electronics. Nuclear engineering -- Electrical engineering. Electronics. Nuclear engineering -- Electronics -- Microelectronics. Integrated circuits
Technology -- Electrical engineering. Electronics. Nuclear engineering -- Electrical engineering. Electronics. Nuclear engineering -- Electronics -- Optoelectronic devices. Photoelectronic devices -- Semiconductor devices
GEM Subject: Science -- Engineering
Science -- Technology
Science -- Instructional issues
Vocational Education -- Technology
Vocational Education -- Instructional issues
Key Concept: Physics -- Currents
Physics -- Semiconductors
Electrical engineering
Manufacturing -- Integrated circuits
Resource Type: Demonstrations
Instructional Materials
InteractiveResource (DCMI Type Vocabulary)
Science Materials
Format: flash
shockwave
Audience: College/University Instructors
Higher Education
Professional Formation
Teaching Professionals
Technical School First Cycle
Technical School Second Cycle
University First Cycle
University Postgrad
University Second Cycle
Vocational Training
Language: English
Access Rights: Free access
Subject: Engineering Education
Date Of Record Release: 2012-12-31 09:54:32 (W3C-DTF)
Date Last Modified: 2011-08-19 13:25:39 (W3C-DTF)
Source Type: ATE Center
Source: NetWorks
Full Record Views: 124
Resource URL Clicks: 17
Cumulative Rating: NOT YET RATED
Report a Problem with this Resource Record

Resource Comments

(no comments available yet for this resource)

user login
Username:
Password:
why log in?
Manage your resources
Save, organize, and share resources that you find.

Subscribe to bulletins
Automatically be notified about new resources that match your interests.

It's easy, fast, and FREE!
Have a favorite applied math or science site you want others to know about?

SUGGEST a
NEW RESOURCE
to add to AMSER

Copyright 2014 Internet Scout Resource Metadata
Copyright 2014 Internet Scout
NSF NSDL University of Wisconsin Internet Scout
Leave Feedback
http://amser.org/