Be your own multivibrator

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Notice anything familiar about the schematic for this Project? If you get the feeling that you've seen this circuit before, you're right. Take a look back at the schematic for Project Divide by 4 counter with line decoder - you'll see that it's the same counter and line decoder circuit without the multivibrator.

This Project lets you be your own multivibrator. As you can see from the schematic, each time you press the Key you send a clock signal to the first flip-flop. The counter circuit is asynchronous since the Q output of the first flip-flop provides the clock signal for the second flip-flop.

Turn the power to ON and press the Key a few times. You'll see LEDs 1 through 4 light up in order and then go off. This cycle will be repeated a few times depending on how many times you press the Key.

Of course, there's several ways to vary this circuit. You could supply the set or reset signal instead of the clock ... or you could let the multivibrator supply some of the inputs while you supply the others.


1. When pressing the Key, don't do it too quickly (fast pressing may result in what we call switch 'bounce'—which means very, very fast un-intentional switch action).

2. Be sure you're using fresh batteries (or you may end up with some strange results).








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