This blog will keep to a simple theme of my tinkering with electronic and computer related toys, gadgets, projects and the like. I do hope from time to time there is something for someone to find when they are exploring these things for themselves. From an early age, I was always attracted to electronic gadgets an I continue to enjoy myself with my hobby. Unfortunately with a busy life, time becomes short an I can not indulge myself like in the past.
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Thursday, December 6, 2012
Elenco's PK-201 Experiment #44: The Flip-flop
This circuit is another variation of the basic multivibrator configuration. This circuit is formally called the bistable switch but is nicknamed the "flip-flop" due to the way it operates. When the lose wire (ground) is touched to the base of the transistor, that transistor is turned off, and the other transistor turns on. One see's that touching the "on" transistor's base turns that transistor and the LED off "flop" and the other transistor and LED turns on "flip". Touching the off transistor's base has no effect (shown in video).
This circuit is a basic building block for digital computers. This circuit can be thought of as memory because it only changes states when one tells it to. In other words, the circuit remembers that the transistor is on even though the wire is removed from the transistor's base. By combining several of these circuits together allows letters or numbers to be remembered and by combining thousands of these circuits a computer can remember a small book. A typical computer has many thousands of flip-flops, all in integrated circuit form. The operation of this circuit is simple. If NPN-left is on then it will have a low collector voltage. Since this collector voltage also connects to NPN-right's base, NPN-right will be off. But if you ground NPN-left's base then it will turn off and its collector voltage rises, turning on NPN-right. NPN-right will stay on until the transistor is grounded.
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