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Issue 5, January 2010                                                                                                      Previous Issues     

Let's drop in on Wily and look over his shoulder at his latest project....

Solar Powered Wireless Sensor

Wily had just returned from his morning walk when he got a call from a company in sunny Florida.  The company was desperate.  They needed a DC power supply for a remote sensor they were developing for one of their larger customers.  The sensor was connected to a low power microprocessor and a RF transmitter.  When switched on, collected data was quickly transmitted in a short burst.  The transmitter drew a peak current of 1 Amp for about 0.01 seconds from a 3v supply.  The transmitter was turned on only once every 10 seconds.  his worked out to an average current from the +3v supply of only 1ma.  The sensor and processor added only another 0.1ma of average current......

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Battery Tester
Rechargeable NiMH
batteries are used in countless electronic products. These batteries make economic sense since one set of rechargeable batteries can be charged and discharged 100s of times instead of throwing away a depleted set of non-rechargeable types each time. There are lots of AA and AAA NiMH
battery chargers available.  Some are designed to quickly charge a battery in as little as 15 minutes.  Although there are lots of ways to charge these batteries there is no easy way to test them.  How do you know if the 3-year-old batteries you have been using are ready for the recycle bin?  If you discover that the 4 AA cells which you use in a digital camera run out of juice after only a few shots, you know that there is one or more of the 4 cells which is bad, but which ones?
story con't on page 6

Yellowstone Might Explode
By: Dave Johnson  

The geology at Yellowstone National Park, here in the U.S., is complex.  The whole area is one big volcano. In fact, some geologist think it might be the largest one on earth.  It appears that the Yellowstone super volcano blows its top every 600,000 years. The last time the place erupted was some 650,000 years ago.   In other words, it is due for another volcanic event.  This event could be a really bad one. .....

  story con't on page 8

New Products 2009
New product announcements are made nearly every day.  I subscribe to many trade journals and each is filled with hundreds of flashy advertisements.  But, only a few of those product ads catch my eye.  Since Iím a circuit designer, I especially like those components that trigger many new application ideas in my mind.  Sometimes it is the smallest products that are the most useful.  I often discovered new products in surplus electronic catalogs.  The surplus companies often buy up stock that came from companies that went out of business.  Bad marketing or bad management may have killed a perfectly good product idea.  Their loss can be your gain if you can spot the bargain.                               
Measuring Low Value Resistors
By: Dave Johnson
Most multimeters are only good down to about plus or minus one half ohm in accuracy.  In many switch mode power supplies and in high current sensors, you would like to know the resistance of a piece of wire, an inductor or a shunt resistors down to perhaps 0.0001 ohm.  When I need to accurately measure the resistance of such a device, I reach for my handy 1 Amp current injector device....

   story con't on page 4

Dirty PC Boards by David Johnson, P.E.          
Several years ago I received a frantic call from one of my clients.  He was having all kinds of problems with some new railroad ice detector units he was building.  I had designed the system for him, so I was quite familiar with the circuit.  He said that there were not just one symptom but instead, there are all kinds.  None of the units would work and some behaved very erratically.  It was a common practice for me to build the first 20 or so units, to make sure that the overall design was....

 story con't on page 3

Bad Computer Power Supplies

For the last 10 years of so, I have built my own computers.  I buy the needed components and assemble them in a metal computer tower case similar to the one shown below.  I feel that this gives me more control of my computer than buying a complete system from a store.  However, I have learned the hard way that the typical computer power supply that often comes with the tower case is not worth using. 

story con't on page 5    

Energy Savings Using Voltage Bucking Transformer

I have read that some people have installed a large inductor in series with their homeís electrical supply to help reduce power consumption.  The idea is that the inductor would have the effect of lowering the AC voltage by shifting the phase relationship between voltage and current.  Could such a device really reduce power consumption and how much would it save?.....

story con't on page 2 

January 2010     Issue 5

Page 1 Back
Good Idea
gone Badly
New Products Rants &
What the World
needs Now
Wily Widget

Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

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