- 1.5V TOUCH ACTIVATED SWITCH
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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- D-FLIP/FLOP ONE SHOT CIRCUITS
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 #1
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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- HONEYBEE COUNTER
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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- On/Off Flip/flop Circuit with Automatic Timeout
This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time. With the components shown, the
output will stay on for only about 20 seconds.
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- PUSHBUTTON ONESHOT AND LATCH
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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- TIME TO DUST INDICATOR
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 hobby circuit section.
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