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Led chaser

    Blog entry posted in 'led fun', December 24, 2011.

    This circuit drives a 8 led strip in bidirectional sequence, without using pic microcontrollers. I just used a NE555 as astable multivibrator and two 4017 decade counters.
    The clock signal from the 555 is sent to the clock pin (14) of both counters. At the start condition IC2 does not work, because its pin 13 takes the positive signal. IC1 drives the leds from 1 to 8. Once the last output of IC1 (pin 11) assumes the high level, the clock enable signals (pin 13) are inverted. So IC1 breaks, while IC2 drives the leds from from 8 to 1.
    The last output of IC2 brings the circuit to the start condition.
    Circuit schematic (pdf)

    http://www.youtube.com/watch?v=8k-ttx2qGaA

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