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Featured Circuit of the Week |
Door Knock Beeper
In some apartment buildings and homes,
not equipped with a door bell, it may be hard to hear someone knocking on the
front door. The circuit below provides a means to activate a loud beeping sound
inside, whenever someone knocks on the door from the outside. The circuit is
powered by a 9v battery, which should provide years of service. An on/off switch
allows the device to be turned off if desired... |
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All Circuits of the Week |
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Featured Circuit Last Week |
Water Seepage Alarm
This simple circuit sounds a beeper when its electrodes detect water. It is
powered by a single 1.5v N cell. A small 1.5v button battery will also work. |
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All Circuits of the Week |
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Dave is
available for consulting projects - give him a call |
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Dave's other websites to visit: |
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collection of resources for inventors,
hobbyists, scientists & engineers |
resource
portal for information
regarding renewable, alternative
or sustainable energy |
Dave
Johnson & Associates -
consulting services for new products from conception to
production or improving the
cost & performance of existing products |
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David A. Johnson, P.E. is an
electronics engineer with over 30 years practical experience in
the areas of analog & digital design, fiber optics and RFID. Electronics is his
vocation, hobby and passion. He is a published author with articles and designs in
EDN, Electric Design, Midnight Engineering and Popular Electronics. Throughout
his career, Dave's imaginative approach to design has resulted in applying new
technologies in creative and cost saving ways. |
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