Category Archives: Electronics

Power Supply Voltage Control Using Current DAC

Posted on 22-June-2013 by mathscinotes

Introduction In this post, I am analyzing the feedback circuit of power supply with an output voltage that is controlled using a current-output Digital-to-Analog Converter (DAC). I analyzed a related situation (voltage DAC) in this earlier post. This exercise started … Continue reading →

Posted in Electronics | 1 Comment

Computing Useful Customer Analogies

Posted on 25-May-2013 by mathscinotes

Introduction Communicating scientific concepts to the public is a tough problem. One of the major issues is that people have a difficult time imagining the relative scale of things -- just try to think of 1000 of something versus 10 … Continue reading →

Posted in Electronics | Comments Off on Computing Useful Customer Analogies

Lightning Protection Math

Posted on 17-May-2013 by mathscinotes

Quote of the Day In the eyes of those for whom you care, beware of valuing good things they might be but aren't, more than those good things that they are already. - A. Orcim Namuh (1997) Introduction I get … Continue reading →

Posted in Electronics | 3 Comments

Calculator to Select Connector for Joining Wires

Posted on 26-April-2013 by mathscinotes

I have written dozens (hundreds?) of small Mathcad function to help me in my daily work. Since I plan to teach another Mathcad class soon, I am gathering examples that might be good to use as application examples. Yesterday, I was working with a customer on selecting wires for supplying power to our products. I used an old calculator that I have decided to show my students in the class. I will discuss how I used this calculator here. Continue reading →

Posted in Electronics | 1 Comment

A Couple of Examples of Characteristic Impedance Calculations in Mathcad

Posted on 12-April-2013 by mathscinotes

Introduction I have been doing some work that involves computing the characteristic impedances of cables. The work has involved creating some tables in Mathcad for comparison with tables from a government specification. Since I am always looking for real-life computations … Continue reading →

Posted in Electronics | Comments Off on A Couple of Examples of Characteristic Impedance Calculations in Mathcad

Epidemiology and Cell Towers

Posted on 10-April-2013 by mathscinotes

Introduction I received a phone call from a cancer epidemiologist last Friday. He had received my name from a co-worker in his department who knows me. This researcher is in the process of researching a cancer cluster near a cell … Continue reading →

Posted in Electronics, Osseo | 2 Comments

Phone Line Impedance Levels: 600 Ohms and 900 Ohms

Posted on 2-April-2013 by mathscinotes

Engineering is a pretty conservative profession -- I have been accused of "abhorring change". Once something gets standardized it stays in place even when it does not make sense. This morning provided me a good example of this. Phone lines in the United States are usually characterized as having a characteristic impedance of 600 Ω or 900 Ω. These impedance levels go back to the early days of telephony (Figure 1). However, all the phone cables we work with are Category 3 and therefore have identical characteristic impedance (~725 Ω). So why the different impedance levels? I had a discussion with one of our telephony engineers about it this morning and all we could do is speculate. I thought I would document this speculation here. Continue reading →

Posted in Electronics, Telephones | 6 Comments

Engineering Application of Conformal Mapping

Posted on 1-April-2013 by mathscinotes

Introduction I have a project that I am working on that involves the use of conformal mappings. I have long found the use of complex numbers in electrical engineering interesting. My first contact with an engineering application of conformal mappings … Continue reading →

Posted in Electronics | 4 Comments

Battery Life Dissipated Under Varying Temperature Conditions

Posted on 6-March-2013 by mathscinotes

Introduction I am not getting any younger. As I age, I have come to realize that certain activities age me faster than others. For example, I have no doubt that sitting in meetings for hours every day has deleterious effects … Continue reading →

Posted in Batteries, Electronics | 1 Comment

Battery Freezing Math

Posted on 26-February-2013 by mathscinotes

I live in a cold climate -- so cold that under certain circumstances we can freeze our lead-acid batteries (Figure 1). A customer who lives in my region called recently and was wondering if I thought any of his batteries would have frozen over the winter. A number of his Internet service subscribers have vacation homes that are unoccupied over the winter. All of these vacation home owners turn off their AC power for the winter. Since all of our Optical Network Terminals (ONT) are connected to Uninterruptible Power Sources (UPS), they will begin operating off of their battery when the AC power goes away. If the home owner does not disconnect the battery, the ONT will run discharge the battery. This is important because a discharged battery will freeze -- a charged battery will not freeze. A battery that has been frozen is very likely a dead battery. Continue reading →

Posted in Batteries, Electronics | Tagged , , | 17 Comments