{"id":127446,"date":"2023-10-12T19:22:00","date_gmt":"2023-10-12T13:52:00","guid":{"rendered":"https:\/\/www.electronicsforu.com\/?p=127446"},"modified":"2024-08-05T17:14:17","modified_gmt":"2024-08-05T11:44:17","slug":"quiz-buzzer-circuit","status":"publish","type":"post","link":"https:\/\/www.electronicsforu.com\/electronics-projects\/quiz-buzzer-circuit","title":{"rendered":"Quiz Competition Buzzer For Eight Players\/Teams"},"content":{"rendered":"
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We designed a Quiz Buzzer circuit<\/strong> that can be used for eight players\/teams in quiz competitions organized by schools or colleges. <\/p>\n\n\n\n

Normally, quiz circuits are designed with microcontrollers, but this simple circuit does not use any microcontroller. The heart of this circuit is a priority encoder, 74LS373. The author\u2019s prototype built on a breadboard is shown in Fig. 1.<\/p>\n\n\n

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\"DIY
Fig. 1: DIY Quiz Buzzer Circuit on Breadboard<\/figcaption><\/figure><\/div>\n\n\n

Components Required<\/strong><\/h2>\n\n\n\n
Parts List<\/strong><\/td><\/tr>
Semiconductors:<\/strong><\/td><\/tr>
IC1<\/td>-LM7805, 5V voltage regulator<\/td><\/tr>
IC2<\/td>-74LS373 priority encoder<\/td><\/tr>
T1, T2<\/td>-2N2219 NPN transistors<\/td><\/tr>
BR1<\/td>-1A bridge rectifier<\/td><\/tr>
LED1-LED9<\/td>-5mm LEDs<\/td><\/tr>
Resistors (all 1\/4-watt, \u00b15% carbon):<\/strong><\/td><\/td><\/tr>
R1<\/td>-1-kilo-ohm<\/td><\/tr>
R2-R10<\/td>-5.6-kilo-ohm<\/td><\/tr>
R11-R18<\/td>-100-ohm<\/td><\/tr>
Capacitors:<\/strong><\/td><\/tr>
C1<\/td>– 1000\u03bcF, 35V electrolytic<\/td><\/tr>
Miscellaneous:<\/strong><\/td><\/td><\/tr>
CON1<\/td>– 2-pin connector<\/td><\/tr>
S1-S8<\/td>– Push-to-on switches<\/td><\/tr>
X1<\/td>– 230V AC primary to 9V, G39 500mA secondary transformer<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Quiz Buzzer Circuit<\/strong><\/h2>\n\n\n\n

Fig. 2 shows the circuit diagram for the quiz competition buzzer.<\/p>\n\n\n\n

It is built around a step-down transformer<\/a> (X1), a bridge rectifier<\/a> (BR1), a 5V voltage regulator LM7805<\/a> (IC1), eight push-to-on switches (S1 through S8), priority encoder IC 74LS373 (IC2), two NPN transistors 2N2219 (T1, T2), a piezo buzzer (PZ1), nine LEDs (LED1 through LED9), and a few other components.<\/p>\n\n\n\n

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