Monday, July 10, 2017

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, July 09, 2017

ET - Technology Interface Journal

Technology Interface ia an on-line journal for the Engineering Technology profession serving education and industry. The Technology Interface has been developed to provide professionals in the Engineering Technology profession and related fields, the opportunity to share ideas concerning teaching, teaching improvements, projects, industrial activities, research and much more via the internet.

ET the Technology Interface - Wayback

"Use of a PC Printer Port for Control and Data Acquisition by Peter H. Anderson Department of Electrical Engineering Morgan State university Abstract: A PC printer port is an inexpensive and yet powerful platform for implementing projects dealing with the control of real world peripherals...."

DMM and Scope

Use of a PC Printer Port for Control and Data Acquisition

"Building an 8-bit PC-Based Logic Analyzer by Kyle C. Quinnell Department of Engineering Technology New Mexico State University Abstract This paper presents a way of using a PC computer as a an 8-bit Logic Analyzer...."

Building an 8-bit PC-Based Logic Analyzer:

delabs Notes

A student can also on his own have a small lab in his house and start building and programming to supplement his academic training. You can build your lab from scratch, build your own test equipment. Start Somewhere. Build something and sharpen skills.

Tuesday, July 04, 2017

Online Museums of Hewlett-Packard

HP Archive  - This site is run by Glenn Robb, an Electrical Engineer and HP aficionado. It's goal is to help others collect, preserve and enjoy vintage HP equipment and literature.

Online Museum of Hewlett-Packard - Ken

"This web site is devoted to the history of test equipment produced by the Hewlett-Packard Company which is now known as Agilent Technologies. I own a huge collection of vintage Hewlett-Packard test equipment, catalogs, equipment manuals, and Hewlett-Packard Journals" -  Kenneth A. Kuhn.

HP's Instrumentation and Technologies Division became Agilent, Recently Keysight a new firm sprang from Agilent as the Heir to the Scopes, Meters, Oscillators and Counters. So in this blog we are relating to Keysight as the continuation of the old HP tradition of Test and Measurement.
(The present hp is a computer company and agilent a health care firm)

Online Museums of Hewlett-Packard

Their first business location in the Santa Clara Valley is the now iconic garage located at 367 Addison Avenue in Palo Alto. Here they manufacture the company's first product, the 200A Audio Oscillator. Disney Studios becomes interested in the 200A and orders eight to be used in the production of their movie, Fantasia.

Keysight Technologies History

"As the company moves into this decade it undergoes a major transformation. In 2013 Agilent Technologies announces that it will split into two separate pure-play measurement companies. The name of the new electronic measurement company is announced later in the year as Keysight Technologies."

The HP Garage is a private museum where the company Hewlett-Packard (HP) was founded. It is located at 367 Addison Avenue in Palo Alto, California. It is considered to be the "Birthplace of Silicon Valley"

HP Memory Project - Vintage Hewlett Packard
"The HP Memory Project is, first of all, a collection of vintage Hewlett-Packard hardware, software, documentation and other technical and marketing materials from HP's early years in the instrumentation and computer industry (beginning in 1939).

Hobby DIY Garage