Author Archives: mathscinotes

Switch-Controlled Circuit To Isolate Battery from Load

Posted on 19-June-2018 by mathscinotes

I recently was asked if it was possible to design a circuit that will isolate a battery from a circuit until a momentary switch is closed (Figure 1). Once the momentary switch is closed, the battery is connected to the rest of the circuit and it cannot be disconnected by further mechanical switch closures. This was just a proof-of-feasibility exercise and NOT a final implementation. However, it was a good example of how to use LTSpice to verify the first design concept and is worthwhile documenting here. Continue reading →

Posted in Electronics | Comments Off on Switch-Controlled Circuit To Isolate Battery from Load

Computing Dates of Fathers Day with Excel

Posted on 17-June-2018 by mathscinotes

My wedding anniversary (16-June) and Fathers Day are on the same weekend this year. Next year, Fathers Day and my anniversary are on the same day. I became curious about (a) how to compute the date of Fathers Day for each year, and (b) determining the years when Fathers Day and my anniversary occur on the same date. Continue reading →

Posted in Excel, Math Education | Comments Off on Computing Dates of Fathers Day with Excel

Air Conditioning Load of a Group of People

Posted on 12-June-2018 by mathscinotes

I was reading an article about HVAC (Heating, Ventilation, and Air Conditioning) calculations in the Journal of Light Construction that had a quote I found interesting. It said that

… 17 extra occupants added more than a half ton of cooling load. Continue reading →

Posted in Construction, General Mathematics, General Science | Comments Off on Air Conditioning Load of a Group of People

Accelerometer Power Calculation Example

Posted on 8-June-2018 by mathscinotes

I am working on a product that uses a Bosch BMA253 accelerometer as a motion sensor. This family of products has become a defacto standard for inexpensive motion detection. In this post, I will provide a simple power calculation example along with some empirical data that Bosch provided me. Normally, I would not consider a simple power calculation worth writing about, but the datasheet did not provide a worked example. I also provide an Excel workbook that parameterizes the critical variables. Continue reading →

Posted in Electronics | Comments Off on Accelerometer Power Calculation Example

State Casualty Rates During the Vietnam War

Posted on 5-June-2018 by mathscinotes

My first engineering manager was named Marl Godfrey. He was an excellent manager who also had keen insights into the human condition. These insights made quite an impression on my 22-year old self – I actually kept a notebook of his comments. Some of his most insightful comments were about the US military and the Vietnam War. Marl has grown up in Oklahoma and he had served in Vietnam. He once commented that Oklahoma had very aggressive draft boards, which resulted in Oklahoma having a relatively high death rate during the conflict. I was reminded of this statement when I recently reviewed my quote database. I thought that I should be able to determine how death rates varied by state during the Vietnam War, which is the subject of this post. Continue reading →

Posted in History Through Spreadsheets | Comments Off on State Casualty Rates During the Vietnam War

Liberty Ship Production Data

Posted on 22-May-2018 by mathscinotes

One WW2 battle that we hear little about was fought by logisticians. Their battle was between what could be produced versus what could be delivered in time to matter.  This point was driven home to me when I heard a WW2 historian say that the US had the manufacturing capacity to produce 150K tanks, but that level of tank production would consume all the US steel and leave nothing to build the ships needed to carry the tanks to the fight. Continue reading →

Posted in Excel, History Through Spreadsheets, Naval History | 2 Comments

Shotgun Bore Diameter Math

Posted on 6-May-2018 by mathscinotes

I have been doing some metalwork lately that involves using units of "gauge". You will find the term gauge used in the measurement of wire, metal thickness, and pipe bore diameter. This quaint, but confusing, measurement system is slowly falling out of favor (example, sheet metal thickness gauge). Continue reading →

Posted in Metrology | 3 Comments

Thanks Team

Posted on 3-May-2018 by mathscinotes

I have now started on my next employment adventure. I can only say thanks to the wonderful team of people that I leave behind. They created the products that allowed the Fiber-To-The-Home (FTTTH) market to flourish. Tens of millions of FTTH products are now manufactured every year by companies around the world. These products are amazing in that for very low-cost they can contain such diverse technology: high-speed digital electronics, FPGAs, RF video,  telephony, battery backup, and wireless. The team can be proud of what they have done. You succeeded where many others failed. Continue reading →

Posted in Personal | Comments Off on Thanks Team

Short-Term Solution for Furnace Condensate Freezing Problem

Posted on 23-April-2018 by mathscinotes

Minnesotan's have endured a cold winter with relatively little snow, a situation that causes the ground to freeze deeper than expected. In northern Minnesota, we plan for 60 inches of frost depth, but this year the frost has gone much deeper. For those cabins with condensing furnaces, this extra frost depth has resulted in many frozen septic lines. This winter, I have frozen both my cabin and garage septic lines. Continue reading →

Posted in Construction | 4 Comments

Number of Space Travelers

Posted on 10-April-2018 by mathscinotes

I was watching physicist Michio Kaku on CSPAN last Sunday night talking about his new book The Future of Humanity. I like watching authors speak on CSPAN because they provide an extended interview format for authors. In this interview, the interviewer Brian Lamb mentioned a factoid as part of a question that I thought was worth investigating. Continue reading →

Posted in Space | Comments Off on Number of Space Travelers