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This simple "Led Cube" circuit generates a random sequence without the use of microcontrollers. It uses a shift register in a configuration called Linear Feedback Shift Register ( LFSR ) .

Step 1: 8 LED Cube at Work

You can arrange the LEDs in any any other configuration you like.

Step 2: Main Components:

IC1: CD4001 ( cmos quad nor gate )

IC2: CD4015 ( cmos dual 4 stage shift register )

IC3: CD4070 ( cmos quad XOR gate )

LED 1-8: any color, any size LEDs.

Step 3: Multivibrator 1 - Sets the Pattern Change Rate.

Step 4: 1 Mhz Oscillator, Shifts the Random Pattern.

Step 5: Differentiator Circuit

enables the 1Mhz oscillator for 150uS (150 microseconds)

Step 6: Linear Feedback Shift Register

This circuit generates random numbers. It is also often used to generate white noise ( a sea-wave type of sound ) which contains all audio frequencies in equal levels. Can be expanded by adding more stages.

Step 7: Anti-lock

If all stages are "0" the LFSR will lock in that state. These 2 components will prevent this by inserting a "1" into stage 1 if this happens.

Step 8: Led Outs

Leds are driven directly from CD4015 outs through current limiting resistors. Value is not critical.

Step 9: For More Details, Watch Video. Thanks!

About This Instructable

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Bio: Music: my profession for over 40 years... Electronics: my beloved hobby always.
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