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THE 4081B LOGIC CIRCUIT

V. Ryan 2003

 

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 shown opposite.
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.

   

QUESTION:
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.

   
 
   

CLICK HERE FOR 4081B CIRCUIT DIAGRAM AND EXPLANATION

   

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