Wednesday, October 19, 2011

Measure resistance and capacitance without an A/D

This article describes how to measure values of a variable resistor or a variable capacitor using a microcontroller to measure the RC charge time to a constant threshold voltage. A variety of these "one-shot" circuits are described and the accuracy of the various methods is measured. Sample programs for the 87C51 family are presented at the end of the article.

Measure resistance and capacitance without an A/D

The old "one-shot" monostable multivibrator circuit has been around since the discovery of the electron. Popular IC versions of this variable pulse width generator include the 74123 and the famous (Philips) Signetics NE555 timer. These circuits use the time to charge a capacitor to a predefined voltage as their time delay.

Measure resistance and capacitance without an AD

If the threshold voltage is 1-1/e (e is the natural log base), then the time delay in seconds is exactly the product of the resistance in ohms and the capacitance in Farads (t=RC). This is a linear equation and it can be used to measure an unknown value of R if C and t are known. The purpose of this article is to describe ways to measure a RESISTANCE by using this technique with an 80C51 type of microcontroller.

by Don Sherman AN449 - NXP Philips Application Notes

Sunday, October 16, 2011

Wiley InterScience - Technical Content

Introduced in 1997 and launched commercially in January 1999, Wiley InterScience is a leading international resource for quality content promoting discovery across the spectrum of scientific, technical, medical and professional endeavors.

Wiley InterScience - Technical Content

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Thursday, October 13, 2011

LED Lighting and LED Lamp Drivers

LED Lighting is gradually replacing CFL Lamps because they are more frugal in drawing energy and last many years. These have been around for some years and the technology is progressing. Now LEDs which show the illuminated objects in their true colors (like sunlight) are also coming. Due to the green initiatives of many countries, people have become aware and also implementing these solutions. These become a necessity when you start using Solar Panels for Home Power.

LED Lighting at delabs Tech

LED Lighting and LED Lamp Drivers

The CFL lamps have reduced the use of the Filament Bulb due to lower power consumption. Now LED lamps may have to replace CFL but it is progressing. Few years ago only Conference Rooms, Media Events or Product Exhibits could afford the LED lighting, it was a Novelty. Now LEDs are affordable and Reliable Driver Solutions are also available.

The problem like in most Tech Learning Curves is now the SMPS drivers for these LED Arrays. The LEDs are reliable, but drive systems are still having problems. Cost effective drive systems from make affordable lighting possible. But due to Quality and Reliability issues, system integrators face implementation problems.

When Mitutoyo the maker of the Best Metric Tools started decades ago, it faced a tough market. In those days, Japanese Goods were known as cheap and low quality in Europe and America.

Companies like Mitutoyo, Sony, Misubishi, Hitachi and many more changed the scenario completely. Now Japan is a Symbol of High Quality and New technology Innovations. Other countries should follow this Golden Example set by Japan and its Products. Every new firm has to go thru those Stages.

A genuine long term commitment to R&D and Quality will build the reputation of Brands, Firms and entire Regions. Anyway, here are some nice resources to help build Drivers and Systems for LED Lighting.

These Semiconductors and Applications are Excellent, the driver systems have to be engineered and perfected by manufacturing and development. A casual or quick results method will backfire. Hence system integrators start by working closely with the vendor (Vendor Development) of Drive Systems. Finally deliver only systems that are Robust and Burnt in. The other option, work with know friendly customers as a Beta Testing and learning phase, till systems reliable for global deliveries.

Contents

Basic Electronics
Basics of Electronics
Product Production
Work Discipline
Testing Points
Learning Electronics
Electronics Theory

Production Notes
Prototype Fabrication
Electrical Circuits
Electromechanical


Library
Scots Guide Electronics
Engineering - Wikibooks
Design Lab - Jim Svoboda
DC Circuits UOG
Socratic Electronics
Blobz Guide Electric Circuits


Product Design
Product Development
Constant Current Source
Good Voltage Regulators
Insulation Resistance
Digital Insulation Tester
DN Schematic PCB 04
DN Product Design 07


Hobby Circuits
VU Meter Circuits
LED brightness control
555 Incredible Chip
Process Control
liquid level measurement
Thermocouples and RTD
Design ADC Interface uC
Thermocouple Amplifier
IA Instrumentation 02
Temperature on DMM
Optical Proximity Switch
Analog Mux - Data Acquisition


Test Measurement
Instrumentation Automation
NI Test and Measurement
DMM Digital Multi Meter
Oscilloscope in T&M
IA Automation 01
Build Instruments
Tektronix T&M Equipment
Educators Corner – Agilent


Power Electronics
UPS Background
Transformer Connections
DN Power Electronics 03
DN Power Electronics 02
Half Bridge Convertor SG3525


Embedded
Interfacing Microcontrollers
Embedded Process Control
80C31 8052 Microcontroller
Microprocessors and uC
Embedded Systems Design

Components
Good Voltage Regulators
Relays and Contactors
Potentiometers Trimpots
Prototype Boards Types
Types of Capacitors
Types of Switches
Resistors How they Work
Coils Transformers SMPS
Mains Transformers Types
DN Components Selection 05

Tutor Gadgets
Count-Up Timer
Digital Logic Gates
Electronics Tutors

History
Teaching Instruments
Charles Proteus Steinmetz
Muntzing a Circuit Design
Teralab Electronics projects
Historical Instruments


Tables, Charts, Videos
Binary and Hex
Resistor Color Code
Ohms Law
Giga, Tera, Pico, Nano
High Resistance Materials

Analog
School - Analog Design
DN Analog Basics 06
DN Op-Amps 01
TI Semiconductors