U3L1FlipFlopApplications

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Problem
	1.	The circuit shown below is a photosensitive event detector. This circuit sounds an alarm if the beam of light between the 12-volt incandescent bulb and phototransistor is disrupted. This circuit would be used as part of a larger burglar alarm system. As the name implies, a phototransistor is a transistor that is sensitive to light. In the event detection circuit, the phototransistor acts as a switch. As long as the phototransistor is in the proximity of the incandescent bulb, the transistor will be on. This, in turn, will hold the CLK input of the flip-flop at a logic zero. If the beam of light is disrupted, the phototransistor will be off. When the transistor is off, the CLK input of the flip-flop will be pulled high through the 5.6 kW resistor. This zero-to-one transition will toggle the Q output to a one, which will turn the buzzer on. The buzzer will remain on until the reset button is pressed. Shown below is a simplified version of the photosensitive event detector circuit. In this simplified version, the phototransistor and incandescent bulb have been replaced with a simple pushbutton switch. This substitution was made because the Multisim does not have the capability to simulate breaking the light beam. a. Using the Multisim, enter the simplified version of the event detector circuit. Be sure to set the frequency and voltage of the buzzer (SONALERT) to 2 kHz and 4.5 volts respectively. Show me your competed design in class or email me a picture if you completed it at home. b. Start the simulation and verify that the circuit is working as expected. Pressing the first push-button switch (Key = Space) will sound the alarm; pressing the second push-button switch (Key = A) will disable it. If the circuit is not working as expected, review your circuit and make any necessary corrections. Did your alarm sound? Answer yes or no.
	2.	The circuit shown is a 4-bit shift register that is used to detect the input sequence 1,1,0,1. When this input sequence is detected, the output Z will be on. At all other times, the output Z will be off. a. Using Multisim, create the 4-bit shift register circuit. b. Start the simulation and verify that the circuit is working as expected by trying various input sequences and confirming that the sequence 1,1,0,1 is detected while others are not. If the circuit is not working as expected, review your circuit and make any necessary corrections. Show me your working circuit or email me a copy if you did it at home. c. Make the necessary modification to the circuit so that it will detect the input sequence 0,1,1,0. Simulate this new circuit and verify that it is working as designed. If not, make any necessary corrections. Show me your working circuit or email me a copy if you did it at home. Did your circuits in part b and part c work correctly? Answer yes or no.
	3.	Modify the shift register designed to detect 1,1,0,1 to use only 74LS74 D flip-flops. In terms of the number of gates used, what is the advantage of using the D flip-flop over the J/K flip-flop? Show me your working circuit or email me a picture of it if you did it at home.