hi, I have an assignment question for a disc cutter for sawing steel stock and needs a digital control system to ensure safety of the operator and equipment. The requirements of the system are as follows: A logic ‘1’ output ‘Y’ will cause the cutting disc to be lowered onto the material to be cut. The same output reset to ‘0’ will return the disc to the raised possition.
Inputs to the system are:-
A: guard fitted (‘1’) guard removed (‘0’)
B: disc speed correct (‘1’) disc stationary or running up (‘0’)
C: end stop (cut complete) readed (‘1’) cut incomplete (‘0’)
D: key switch to ‘operator’ (‘1’) key switch to ‘off’ (‘0’)
E: key switch to ‘maintenance’ (‘1’) key switch to ‘off’ (‘0’)

The disc will be allowed to lower under the following conditions:
 Guard fitted and speed correct and & end stop not reached & key switch to ‘operator’.
 Guard fitted and speed correct & end stop not reached & key switch to ‘maintenance’.
 Guard removed & disc stationary & end stop not reached & key switch to ‘operator’.
 Guard removed & disc stationary & end stop not reached and key switch to ‘maintenance’
 Guard removed, & speed correct & end stop not reached & key switch to ‘maintenance’.

For the above scenario, design a combinational logic control system that will satisfy the above criteria for lowering the cutting disc. Design data should contain at least:-
i) Truth Table
ii) Full logic expression for ‘Y’ (output)
iii) Logic expression minimised by boolean algebra
iv) Karnaugh maps for Y & Y accounting for ‘don’t care’ states
v) AND, OR, NOT soluctions for Y & Y.
vi) NAND & Nor solutions for Y & Y.

I have done the truth table, and the full logic expression for Y, the problem is, i can't do the karnaugh maps accounting for the 'don't care' states as i dont know how do determine them, its been a while sinse iv dont this kinda stuff. I would appreciate it if someone could give me some insight into how to work out these 'don't care' states. i have attached the truth table. thnx

Attached Files

logic1.xls (14.0 KB, 10 views)