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# Monthly Archives: December 2010

## Dual Modulus Counter Design Example

Quote of the Day I have long been of the opinion that if work were such a splendid thing the rich would have kept more of it for themselves. — Bruce Grocott, British politician Introduction One of the more common … Continue reading

## Little Stories from the History of Science and Technology

Introduction I have always been interested in the connectedness of people. The theory that each of us is separated by only six degrees from anyone else is a theory I like to test. If you examine things carefully, you may … Continue reading

## Test Time and Estimating Bit Error Rate

Test time is expensive. Since our products need to conform to industry standards for Bit Error Rate (BER), we need to test for BER. It is important that we test long enough to ensure that we meet the requirements, yet not so long as to spend more money than we need to. Continue reading

## Calculating the Earth's Age

I have been listening to the audio book The Disappearing Spoon, which is an excellent tale about all of the elements of the periodic table. Of particular interest to me was the discussion of how geologists date the age of the Earth using ratios of uranium and lead. The book also discusses determining the ages of meteorites and the Sun. The discussions were interesting enough that I thought I would look up some additional information. As frequently happens, I was amazed at the amount of information on the web about this subject. This technique has been around since 1956, when it was first used to date meteor fragments from a well-known impact site (Figure 1). Continue reading

## Power Dissipated in a Maximum Phone Load During Ringing

I am writing a specification this morning and I realized that I have never calculated the maximum power drawn by a phone during ringing. I was surprised by the number – 3 W. This is a lot for unit that … Continue reading

Posted in Electronics
1 Comment

## Thermal Runaway Model of Lead-Acid Battery (Part 2)

Derivation of the Output Power Equation The output power equation (Equation 3) is really a restatement of Newton's law of cooling. Equation 3 states the battery's steady-state power dissipation is a linear function of the battery's temperature and the ambient … Continue reading

## Thermal Runaway Model of a Lead-Acid Battery (Part 1)

Introduction Very nearly every product we make ships with one or more lead-acid batteries. Since we have built hundreds of thousands of units, that is a lot of batteries. While most people encounter batteries everyday, few really understand the problems … Continue reading

Posted in Batteries, Electronics
4 Comments

## Laser Failure Rate Estimate Example

I have spent some time lately talking to people about laser failure characteristics. Most electronic component reliability modeling is done using the exponential probability distribution, which assumes the components have a constant failure rate and there is no wear-out mechanism. It turns out that lasers have a wear-out mechanism, which means the exponential probability distribution is not appropriate. Laser failure rates are usually modeled by a lognormal probability distribution, as are the failure rates of brakes (Figure 1) and incandescent light bulbs. These components have reliabilities that are dominated by wear-out mechanisms that accelerate when damage to a small region grows exponentially. A good example would be a hard spot on a brake pad that becomes hot during braking relative to the rest of the pad. This hard spot tends grow quickly because the heat generated during braking concentrates there. Continue reading

## Calculating Drawer Heights

Introduction As you can tell from all the recent posts on construction, I am in the middle of planning some remodeling on my home. One of my projects includes designing a chest of drawers. It turns out that there are … Continue reading