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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2012
Module Title: Industrial Electronics 2
Module Code: ELEC 6025
School: Mechanical, Electrical and Process Engineering
Programme Title: Bachelor of Engineering in Electrical Engineering – Stage 1
Programme Code: EELEC_7_Y
External Examiner(s): Ms Mary Desmond, Mr Colm Murray Internal Examiner(s): Dr Pascal O’Connor
Instructions: Answer THREE questions. All formula for calculations must be shown.
Duration: 2 Hours
Sitting: Autumn 2012
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
Q1. (a) Fig.Q1(a) shows a logic circuit with two inputs (A and B) and one output Z (a LED).
(i) Develop a Truth Table for this circuit. (ii) Derive a Boolean expression for the output Z. (iii) Simplify this expression and state the input conditions necessary for the LED ON mode. (12 Marks)
Fig.Q1(a)
(b) Develop a logic circuit that has a High Output when at least two out of three inputs A, B and C are Low by,
(i) Creating a Truth-Table for this function, W. (ii) Write a Boolean equation from the truth-table. (iii) Simplify or Minimise this equation, if possible. (iv) Implement the equation in (iii) using AND-OR configuration. (v) Implement the equation in (iii) using NAND gates only.
(21 Marks)
AND
NOT
OR_
LED
220
A
C 0 B
THUMBSWITCH-HEX
AB
AND
OR_
U
NOT
AND
Z
Q3. (a) Simplify the circuit in Fig.Q3(a) by using either a Truth-Table or the rules for Boolean Algebra. Draw the simplified logic circuit (12 Marks)
Fig.Q3(a)
(b) For the circuit in Fig.3(b), detect when two adjacent buttons are pressed. Design a Truth-Table, obtain a Boolean/logic expression and draw the circuit.
Fig.Q3(b) (9 Marks)
(c) Develop the Truth-Table for the Half-Adder and hence state the Boolean equations for the Sum and Carry outputs. Draw a logical circuit diagram for the entire Half-Adder. Show how two Half-Adders may be combined to form a Full-Adder.
(12 Marks)
LED
220
A
C 0 B
THUMBSWITCH-HEX
AB^ Z
A
R
10k
B
R
10k
C
R
10k
5V
Q4. (a) For the diagram shown in Fig.Q4(a), calculate all the currents and voltages around the circuit for R 2 = 10kΩ, (assume βDC = hFE = 50 ; the ON-mode for the 2V LED is ; Iz(MIN) = 1mA for Zener diode). Is the LED ON? (Outline any assumptions you make.) (20 Marks)
Fig.Q4(a)
(b) If R 2 is reduced to 2.5kΩ, what effect, if any does this have on the circuit? (recalculations must be provided.) (13 Marks)
