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D-FLIP/FLOP OSCILLATORS (19) (dfliposc2)
Yes you can turn flip/flop ICs into low current
oscillators. This schematic shows you how. |
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PUSHBUTTON ONESHOT AND LATCH (52) (4013oneshots)
This circuit uses a single IC to convert a noisy
pushbutton switch signal into a clean pulse or a
sustained push on-push off signal. It can operate
from 3v to 18v. |
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D-FLIP/FLOP ONE SHOT CIRCUITS (68) (dflip1shots)
Yes you can use cheap D flip/flop logic circuits as
nice one-shot pulse generators. This schematic shows
how the popular CD4013 and the CD74HC74 can be used
to generate pulses ranging from nanoseconds to
seconds. |
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FLASHING LED ADVERTISING BADGE (81) (badgfls1)
I have seen numerous flashing light badges at trade
shows and conventions. They are often handed out as
gifts to promote some business. The devices often
use inefficient circuits, which cause the battery
power source to be quickly depleted. My circuit is
simple but efficient enough to provide months of
continuous LED flashing. It also has a tiny
push-button switch to turn on and off the light
flashing, extending battery power. |
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TIME TO DUST INDICATOR (85) (dust2)
I thought about this circuit when I heard that a lot
cleaning personal in hotels were either dusting
rooms more often than necessary or not enough. I
have not yet built and tested this circuit
completely but in concept it should work. The
circuit draws very low current from a +3v battery
and could be housed in a package similar to a small
ashtray. The assembly might be placed in a suitable
out of the way area to collect dust. It would alert
a maid when it was time to dust the room. The
circuit detects dust with an infrared LED that is
pulsed so its light shines onto a smooth flat plate.
Any dust settling onto the surface is detected by a
phototransistor, mounted at a 90-degree angle from
the LED. When the dust reaches a particular level,
sufficient light is reflected into the
phototransistor to change the logic state of the
circuit to an alarm condition. The alarm output
could be connected to a beeper, a flashing LED or to
one of the LED flashing circuits in this Tutorials
circuit section. |
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HONEYBEE COUNTER
(86) (beectr)
I designed a circuit similar to this one a long time
ago to help a beekeeper count the number of bees
going into or out of a hive. The low power circuit
uses a slotted opto-sensor to detect the passing
bees. The circuit advances an electronic counting
module whenever a honeybee passes through the
sensor. The device only counts the number of bees
going through the sensor. A different circuit would
be needed to count the number of bees only going out
or only coming into the hive. |
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1.5V TOUCH ACTIVATED SWITCH (102) (mom1v1)
A single 1.5v silver oxide button cell powers this
complete touch activated switch circuit for 5
years. It features both a normally open and a
normally closed set of solid-state switch thermals.
It also has an adjustable sensitivity, which can be
set for a touch capacitance change as small as 1
picofarad. |
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-3V
CAPACITANCE PROXIMITY SWITCH (108) (3VTCHMOM2)
This circuit was designed to provide a touch
activated switch function without an external power
supply. It draws so little power that a single 3v
battery will operate the circuit for many years. It
is discussed in more detail in the section on
Capacitance Proximity Switch Technology. (Note:
link is off-site) |
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FLASHING LED ADVERTISING BADGE (125) (badgfls2)
This circuit is similar to schematic #81. It uses a
CD4013 dual D Flip/Flop IC. The 74HCT74 IC in #81
does not always work. As in #81, a single lithium
battery will provide months of continuous LED
flashing. It also has a tiny push-button switch to
turn on and off the light flashing. |
