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|THE 4081B LOGIC CIRCUIT|
|V. Ryan © 2003-2022|
|Logic gates are usually electronic circuits (based on an integrated circuit) and they are used to make simple decisions. A good example of this type of circuit is based on the 4081B integrated circuit (IC) which can be used effectively in school projects.|
|For example, a dog owner wants to build an automatic
animal feeder to work at night and when his dog presses a switch
(pressure pad). This type of device would automatically feed the dog
when the owner is asleep. A diagram of a simple prototype design is
The 4081B integrated circuit will detect when the two switches are activated, one by the dog and the other as darkness falls - the motor allows food to be released from a tube. If only one switch is activated, food will not be released.
|The logic diagram is shown below. A micro-switch (pressure pad) is used as one input device and a dark sensing circuit as the other. The AND gate has two inputs. If both are activated - the dark sensor and the micro-switch - the logic state of the output changes to high and the motor releases food to the hungry dog.|
|The diagram below shows that the micro-switch has not been pressed and that it is daylight, consequently the motor is off.|
Draw the diagram of the sensors and logic circuit above but it must clearly show the motor working. Show and explain the logic states of inputs and outputs.