Here is a basic project “Simple Quiz Display” using two different TTL ICs. Simple quiz display indicate which of the switch is pressed first among connected switch (i.e. four) by glowing its corresponding LED, where rest of LEDs is remains off.
Circuit Description:- The entire circuit of simple quiz display is build and fabricated around two TTL IC. IC1 is BCD to decimal decoder (7445) where IC2 is Dual 4-input NAND gate (7420). The four push-to-on switch SW1 through SW4 is connected to pin 2, 3, 6 and 7 of IC1 respectively. The corresponding output is taken from pin 9, 10, 15 and 16 by connecting LEDs. SW5 is used to reset the quiz display circuit.
Resistors (all ¼-watt, ± 5% Carbon)
R1 – R4, R9 = 1 KΩ
R5 – R8 = 680 Ω
IC1 = 7445 (BCD to decimal decoder)
IC2 = 7420 (Dual 4 – input NAND gate)
LED1 – LED4 = four different color LEDs
SW1 – SW5 = Push-To-On-Switch