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Issue 13,  November 2011- Page 1                                                                                               Previous Issues     
  

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

Touch Activated Battery Powered Latching Relay

Wily was just finishing his first cup of coffee when he got a call from a home remodeling company.  They needed a custom touch activated switch for one of their clients.  Wily sipped his coffee as the caller described the switch. 

The unit needed to be fairly small.  It would be wired into the underside of some kitchen cabinets.  A wire from the touch switch would be connected to a strip of copper tape mounted just under the lip of the cabinets and would serve as the touch sensor.  When touched, they wanted a relay to switch 120vac power to a string of fluorescent or LED lights, mounted under the cabinets. 

With each touch of the strip, the lights would toggle between an on and off mode.  The total light power was to be less than 100 watts.  Wily gave this request some thought and decided he would take on the project....

con't page 7

Wily Widget,
the Lone Inventor
 with Gadget & Gizmo

WHAT THE WORLD NEEDS NOW is a....
                   Broadband Antennas for Metal Shops                                  
I recently moved to Lubbock Texas.  Iím still in the process of setting up my new electronics lab in my 30 foot by 40 foot all metal shop.  The shop is some 100 yards from the back of my house.  Although I have good cell phone, WiFi and Cordless phone signal strength over my entire acre lot, all those signals drop to zero once inside my shop.  The metal acts as a large Faraday shield, blocking nearly all RF.  The only radio signal which we can pick up inside comes from a strong AM station, whose radio tower is close by.  Nearly all other AM and FM stations are useless.  I sure wish there were some kind of broad band antenna system which could route RF signals into and out of a metal shop.....
story con't on page 6
Tiny Solar Panels Using Photodiodes
By: Dave Johnson
There are times when you would like to harvest just a little bit of energy from the sun.  Unfortunately, there are not many miniature solar panels available.  Most panels are 10 to 50 times larger than needed. One way to make your own miniature solar panel is to wire multiple small photodiodes in series. The result might look something like the drawing below, which is a made from 12 small BPW34 photodiodes.  This panel is about ĺ of an inch in each side and can produce about 6 volts at a milliamp.  This may not sound like much but for many applications it is plenty.  Even smaller arrays are possible if less power is needed....

   story con't on page 4

Super Hot Ferrite Transformer

I got a desperate call from an ultrasound cleaning machine company.  For many years they had successfully been making 350w units, which ran off 120vac and drove 6 big 40KHz piezoelectric transducers. But when the manufacture of the big ferrite driver transformers they used in their driver board went out of business, they were forced to find a replacement from another company.  But, they could not seem to get a replacement transformer to work properly. Transformers from their new supplier would work for a while but soon got so hot, they smoked. What were they doing wrong?....

 story con't on page 3

 
Bad Magic Mesh Screen
I saw this product advertised on TV a while back and thought I would give it a try for my shop.  I have to leave the shop steel door open to maintain an RF connection to the house through the cordless phone system.  This leaves the door open to bugs of every description.  We thought this Magic Mesh thing might be a good solution.  Well, it does not work for me....

story con't on page 5    

Long Range Laser Communications
I got an email from a hobbyist who wanted to know if a visible red laser pointer could somehow be used in a long range free space communications link, specifically an optical Ethernet.  He really wanted to know the practical range of a system using a cheap visible red laser pointer.  Based on my experience in similar systems, I have a pretty good idea how far it could go but letís run some quick calculations and see what is really possible....

story con't on page 2 


November 2011

Page 1 Back
Envelope
Circuit
Diagnosis
Experimenter's
Corner
Good Idea
gone Badly
What the World
needs Now
Wily Widget


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