1. controlling 8 aircraft avionics system using 5 switches
Submitted By
Redhawan Raziur Rouf
Mohammad Abu Nayem
Zeba Munawara
Shah Mahmud Yasin

3. Content OBJECTIVE GIVEN PROBLEM CONDITIONS NECESSARY COMPONENTS
TRUTH TABLE AND EXPRESSION BASED ON THE GIVEN CONDITIONS
LOGIC DIAGRAM
SIMPLIFICATION OF THE DESIGN
TRUTH TABLE AND GATE DESIGN OF SN74138
IMPLEMENTED CIRCUIT DIAGRAM
RESULT
CONCLUSION

4. Objective To solve the given problem Ensure better design
Ensure economical perspective

5. GIVEN PROBLEM
Suppose in a commercial aircraft there are 8 main avionics system. Each system is switched ON and OFF by its own individual switch. Let for three of the systems, their ON-OFF switch has become unserviceable (faulty).The avionics systems are serviceable and can be operated individually. Design a logic circuit that fulfils the following conditions-
Utilize five systems to operate eight avionics systems individually. However, out of these five, one switch should be “Master ON” switch and one switch should be dedicated as “Master OFF” switch.

6. Conditions 5 switches are to be used
two of the switch should be dedicated for “Master ON” and “Master OFF”
three switches are to control the 8 systems

7. Necessary components Trainer Board 3 to 8 decoder(74138)
Inverter(7404)
EX-OR gate(7486)
Connecting wires
8 LEDs to represent 8 systems

8. truth table AND EXPRESSION based on the given conditions
D0, D1 …………D7 are outputs.
A, B & C are the switches
Expression: D= A’B’C’+ A’B’C+ A’BC’+ A’BC+ AB’C’+ AB’C+ ABC’+ ABC
Inputs
Outputs A B C D0 D1 D2 D3 D4 D5 D6 D7 1

9. logic diagram

10. Simplification of the design
Implementing the earlier logic diagram is complex
Instead we used SN74138, which is a 3 to 8 decoder
The truth table and inside logic diagram for this IC is given.

11. Truth table and gate design of SN74138

12. IMPLEMENTED Circuit diagram

13. Image of the implemented circuit

14. Result The system worked perfectly with three switches
The master ON and OFF switches worked perfectly without any malfunction

15. Conclusion The system worked perfectly.
Inverter was used to invert the logic low output of the 3 to 8 decoder.
In real life this circuit can be easily applied and it will help the pilot to control 8 systems with three switches.