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This is a
very basic circuit for flashing one or more LEDS and also to
alternately flash one or more LEDs.
It uses a 555 timer setup as an astable multivibrator with a
variable frequency.
With the preset at its max. the flashing rate of the LED is about
1/2 a second. It can be increased by increasing the value of the
capacitor from 10uF to a higher value. For example if it is
increased to 22uF the flashing rate becomes 1 second.
There is also
provision to convert it into an alternating flasher. You just have
to connect a LED and a 330ohm as shown in Fig.2 to the points X
and Y of Fig.1. Then both the LEDs flash alternately.
Since the 555
can supply or sink in upto 200mA of current, you can connect upto
about 18 LEDS in parallel both for the flasher and alternating
flasher (that makes a total of 36 LEDs for alternating flasher).
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