ENGR 1
Digital Circuits Laboratory
Team Members __________________________
Materials
1 - LS7400 Quad NAND gate
4 - LEDs
4 - Resistors, 470 – 560 Ohm
Misc Wires
Breadboard
5 V Power Supply
Following the powerpoint demonstration:
1) Build the simple NAND gate demonstration circuit with LEDs
2) Verify the truth table for a NAND gate and get signed off
3) Build the Flip Flop circuit and demonstrate it’s peformance
4) Do ONE of the following design problems as a GROUP
NAND CIRCUITS
(build or simulate it at http://www.jhu.edu/~virtlab/logic/logic.htm)
a) 3 Input AND out of NAND gates
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b) 3 Input NAND out of NAND gates
c) 4 input NAND
(Simulate only)
d) Using only AND, NOT, and OR produce a three-input OR circuit, ie., the output is 1 if any of the
inputs is 1.
e) Create a two-input "adder" with two outputs: the one-digit result of the add, and the value of a
"carry" bit. In binary arithmetic, 1+1=0 with a carry=1.
f) SUPERBOWL PROBLEM
At the beginning of halftime during the Superbowl,
 35 million toilets are flushed almost simultaneously.
 Resulting loss of water pressure wreaks havoc on many municipal water systems.
Make a controller to solve the problem for a "three toilet" system.
 Devise a logic circuit whose "1" inputs represent "flushes"
 and whose "1" outputs represent opened water valves
 If no more than one toilet is flushed, then that toilet's water valve opens,
o the others remaining closed.
 If more than one toilet is flushed, then all the water valves remain closed.