Monthly Archives: February 2013

Interesting Historical Note About Cheese

Posted on 27-February-2013 by mathscinotes

Interesting Historical Note About Cheese I like blog posts that go into the history of common things. This post does a nice job discussing cheese and its long history.

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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

Russian Meteor Characteristics

Posted on 20-February-2013 by mathscinotes

A meteor exploded over Chelyabinsk, Russia (Figure 1), at 3:20 UTC on February 15, 2013. I have been reading accounts of the size, speed, and energy of the meteor. This post presents some simple calculations that verify the consistency of the expert's estimates on the meteor characteristics. Also, I thought it would also be interesting to look at the amount of overpressure required to cause the sort of damage that was seen after the meteor and to include some explanatory material as to how scientists determine the characteristics of a meteor. Continue reading →

Posted in Astronomy, Electronics | 1 Comment

Battery Outgassing Math

Posted on 12-February-2013 by mathscinotes

I recently have received a number of questions about the outgassing of hydrogen gas that can occur from lead acid batteries when they are being overcharged. I thought it would be useful to review what is happening when a battery is outgassing. When being charged, batteries can release enough hydrogen gas to create an explosive hazard. Consider this report and Figure 1 as an example as to what can happen. With lead-acid batteries, hydrogen gas can be generated any time, but charging is when the greatest challenges are faced. Continue reading →

Posted in Batteries, Electronics | 20 Comments

AC Backup Power Using A Simulated Sine Wave

Posted on 3-February-2013 by mathscinotes

Quote of the Day Whenever you want to marry someone, go have lunch with his ex-wife. - Shelly Winter Introduction A customer today requested an AC-output Uninterruptible Power Source (UPS) for our indoor Optical Network Termination (ONT) products. Product Management … Continue reading →

Posted in Electronics | 5 Comments

Great discussion of Saturn's Polar Hexagon

Posted on 2-February-2013 by mathscinotes

This particular post discusses a very interesting laboratory experiment that illustrates how the hexagonal region at Saturn's pole may form. Continue reading →

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