Download Electromagnetic Relays - Industrial Electronics - Past Exam Paper and more Exams Industrial Engineering in PDF only on Docsity! Page 1 of 3 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Autumn Examinations 2009 Module Title: Industrial Electronics 2 Module Code: ELEC 6025 School: Electrical & Electronic Engineering Programme Title: Bachelor of Engineering In Electrical Engineering - Stage 1 Programme Code: EELEC-7-Y1 External Examiner(s): Mr. Gerard Beecher Dr. Maeve Duffy Internal Examiner(s): Mr. Richard Daly Instructions: Answer Three Questions All formula for calculations must be shown Duration: Two Hours Sitting: Autumn 2009 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. Page 2 of 3 Q1 (a) Construct a 5-column binary table with appropriate headings to represent the decimal numbers from 0 to 15 and four binary data bits. Write the decimal digits in the left hand column. 7 marks (b) Draw the circuit logic symbols and truth tables for, a 2-input AND gate, and a 2-input XOR gate. 8 marks (c) Show how the gates in (b) can be connected to construct a half-adder. Include in your answer the truth table for the half-adder. Explain where a half-adder is used in an adding circuit. 5 marks (d) Show by means of a block-diagram, the inputs and outputs for a full-adder. 3 marks (e) Using the block diagram in (d) draw a block diagram for a 4-bit adder. Show the output result for the addition of: P data = 1111 and Q data = 1110 10 marks Q2 (a) Explain in relation to d.c. electromagnetic relays, the terms Pull-in voltage and Drop- out voltage. Give a typical voltage for each case using the relay in Fig 1. 6 marks Fig. 1 is a basic light activated switch. Given that the guaranteed LDR range is 4kΩ to 100kΩ, calculate for the circuit: (i) The relay current when connected to 12V directly; 3 marks (ii) The minimum base current (IB) required to provide the current in (i); 3 marks (iii) The base current when R1 is exposed to light; 6 marks (iv) The voltage at the base when R1 is covered. 6 marks (b) Using the answers in (a), indicate if the relay will energise and de-energise in the range of LDR resistance shown. 6 marks (c) Explain why the diode is connected across the relay coil. 3 marks Fig. 1
