The 4017B Decade Counter- Dice Circuit

This circuit uses the 4017B decade counter. Decade counters give an output at each of the output pins- in turn. So the first output pin will give an output signal and switch off, followed by the second and so on. In order to do this pin 14 has to be provided with an astable signal, and this circuit uses an NE555 timer to provide this signal. When the 'trigger' is pressed the LEDs will light in turn and when the trigger is depressed , the last LED that was lit will remain alight. This is due to the absence of the astable signal which allows the 4017B to switch to the next output. A rocker switch could be used for the trigger or a simple non locking switch, it doesn't matter. The frequency of the 555 timer's output will determin how fast the LEDs will alternate; a low value of the two resistors and the capacitor is reccomended, as this will prevent you from being able to guess which LED will light up when the trigger is turned off.

Parts list

• 1 NE555 timer
• 1 4017B decade counter
• 6 Red LEDs
• 6 330 ohm resistors
• 2 100 ohm resistors
• 1 variable capacitor
• 2 rocker switches
• 1 9V power supply (e.g PP3 9V battery)
• 1 Breadboard or similar

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