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.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ – R₄, R₉ = 1 KΩ

R₅ – R₈ = 680 Ω

Semiconductors

IC₁ = 7445 (BCD to decimal decoder)

IC₂ = 7420 (Dual 4 – input NAND gate)

LED₁ – LED₄ = four different color LEDs

Miscellaneous

SW₁ – SW₅ = Push-To-On-Switch