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Description:
This
is a touch controled switch which keeps the circuit on about 100 seconds
after touching the plate connected to the 2 numbered pin. At the end of
this time duration, relay releases and the circuit gets to off
position.
The impedance of the trigger input of the 555 timer
IC is very high and the inductive voltage on the human body is enough
to trigger it. The circuit works based on this principle. You can use a
piece of metal as a plate. The circuit can be used in toy circuits,
buzzers or any project that is suitable. You can adjust the duration
time by changing the R1 and C1 values.
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Description:
The circuit above is an light sensitive automatic switch which functions in absence of light. The IC 4060 works as an oscillator and the generated signal is applied to the base of T4 transistor. Phototransistor T3 is in conduction by existence of light and it keeps the T5 transistor's base at ground potential.
When no light reaches the phototransistor, it gets in insulation. T3 reaches positive potential through 22kohm. T4 and T5 both gets in conductance. The oscillator signal reaches the optic coupler and lamp(s) shines.
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Description:
This is a two part infrared remote controller circuit that consists of a
transmitter and a receiver circuit pair. When you push the button on
the 9V supplied transmitter circuit, a signal at 38kHz frequency is
applied on the Infrared (IR) LED. As a result of the current passing
through the IR LED, it illuminates the surround with infrared light.
By using the 1k potentiometer, oscillator frequency should be adjusted
to 38kHz to operate the circuit properly.
The illuminated infrared light is detected by the IR receiver module.
Generally IR modules has three pins and in our project we used the
product of Telefunken, TK19 module. Instead of TK19, as an option you can use the SFH506 which is a product of Siemens or any other module for this purpose.
When the IR light touches the receiver, the third pin of the module sees
logic-0 (low). Other case it is in the logic-1(high) position. So
controlling the third pin gives us the information whether the button
on the transmitter is pushed or not.
The J-K type flip flop in the receiver circuit controls the relay. When
the button is pushed, relay gets in the position closed which was in
open position before. So the device gets connected to the mains and
starts operating. After second push, relay gets in position open and
cuts the device energy...
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