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Category Archives: Electronics
Telephone Ring Trip Math
As you can tell by my recent posts, I am doing quite a bit of traditional landline phone math lately. The problems are not very complex, but their resolution is important to delivering quality voice service. Today, I have been working on the circuitry that determines when a phone has gone off-hook. Continue reading
Posted in Electronics, Telephones
5 Comments
Measuring Telephone Ring Power
I have been looking at some power data for telephone circuits today and this data provided a useful empirical check on the theoretical calculations that I have done elsewhere. When I showed the data to some other engineers, they had some good questions that I thought would be worth covering here. Continue reading
Posted in Electronics
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Yet Another Thermistor Discussion
I thought enough people may want to see this slight variation that it would be worth putting into a separate post. It turns out the optimal linearization value for RS is exactly the same as for my original post. This result makes sense if you think about it a bit because a nearly linear output across one resistor in the circuit implies a linear voltage across the other. You can derive this result rigorously using the same approach I used in the Appendix of my original post. Continue reading
Posted in Electronics
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Phone Line Length Math
We make ONT products that provide telephone service in addition to data and video services. I was asked today what limits the length of a standard POTS phone line from an ONT. Most ONTs today are specified to drive a phone line less than 1000 feet long. As I started to write down my answer, I thought that this was a nice application of simple DC electronics and was worth documenting here. Continue reading
Posted in Electronics, Uncategorized
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555 Timer Math
Quote of the Day With hard work, difficult material can be grasped. Step by step, incrementally, the novice can become the master. — Joshua Waitzkin. World Tai Chi champion and subject of the book 'Searching for Bobby Fischer'. He is … Continue reading
Posted in Electronics
8 Comments
Inductive Car Sensor Math
Introduction Spring has come to Minnesota and I want to build an outdoor electronics project -- this is one of my favorite activities. I have decided to build a car sensor for my cabin in northern Minnesota. This car sensor … Continue reading
Posted in Cabin, Electronics
2 Comments
Using a D-Size Battery String for a UPS Energy Source
Quote of the Day If there is one thing more than another for which I admire you, it is your original discovery of the Ten Commandments. — Thomas B. Reed to the youthful Theodore Roosevelt about his self-righteousness Introduction I … Continue reading
Posted in Batteries, Electronics
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A Simple Frequency-to-Voltage Converter
Quote of the Day We are what we repeatedly do. Excellence, then, is not an act, but a habit. - Aristotle Introduction I often build small electronics projects for use around my home. I recently put together a small sensor … Continue reading
Posted in Electronics
41 Comments
Schmitt Trigger Design Math
I have a home project that requires me to design a Schmitt trigger circuit. There are numerous places on the web where you can find design equations for the Schmitt trigger constructed using an open-drain comparator. Unfortunately, these design equations do not model the output low-level saturation voltage of the comparator and in my application I need to be concerned about this voltage. My objective is to determine formulas for the resistors in the circuit as a function of the various threshold and output voltage levels I require. Continue reading
Posted in Electronics
14 Comments
Mathcad Solution to an LVPECL to LVDS Matching Problem
Introduction A circuit question walked into my cube the other day. An engineer in another group was working his way through an application note and he found the presentation unclear -- I agreed with him. The application note provided an … Continue reading
Posted in Electronics
1 Comment