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quiz buzzer with ic 555 timer pdf

I want abstract for quize buzzer using 3 555
timer ic
Manual buzzers used for quizzes in schools and universities create a lot of confusion by identifying the first respondent. Although there are circuits that use discrete PCs and ICs, they are too expensive or limited to only a small number of players. The test ring circuit offered here can be used for up to eight players, which is the maximum in any test competition. The circuit uses IC 74LS373 and some passive components that are available in the market.

[Image: 9EC_may_1_efy.png]

The circuit can be divided into two sections: power supply and test bell. Fig. 1 shows the power supply section. The 5V regulated power supply for the test buzzer section is derived from the AC mains. The 230V AC network is reduced to 7.5V AC by the transformer X1, rectified by the bridge rectifier BR1, filtered by C1 and regulated by the regulator IC1. Condenser C2 prevents waves at the regulator output.

Fig. 2 shows the section of the test buzzer. At the core of this section is IC 74LS373, an octal latch used to transfer the logic state at the data input pins D0 to D7 to the corresponding outputs Q0 to Q7. The data pins D0 to D7 are normally drawn by the resistors R1 to R8, respectively.

[Image: 2A5_may_-55-_-efyh.png]

One terminal of the push-to-on switches S1 to S8 is connected to + 5V, while the other terminal is connected to the respective data input pins. Switches should be extended to players through the cable. The BL1 to BL8 torch bulbs can be stored in boxes with the front side of the boxes covered with white paper with the name or number of the written contestant to facilitate their identification. Place the pictures above the level of the head so that they can also be seen by the audience.

When power is turned on with switch S9 (terminals 'A' and 'B' of both power supply sections and test buzzer are interconnected), the circuit is ready for use. All switches (S1 to S8) are now open and the outputs from Q0 to Q7 of IC 74LS373 are low. As a result, the gates of the silicon-controlled rectifiers SCR1 to SCR8 are also low.

As soon as a contestant momentarily presses their respective switch, the corresponding output data pin becomes high. This triggers the corresponding SCR and the respective light bulb illuminates. At the same time, the piezobuzzer (PZ1) sounds like the transistor T1 leads.

Simultaneously, the base of transistor T2 becomes high to be conductive. The IC2 locking activation (LE) pin 11 is grounded to block all outputs from Q0 to Q7. This restricts the additional change in the output state due to any change in the state of switches S1 to S8 by any other contestant. Only one of the eight torch light bulbs illuminates until the circuit is reset by the on / off switch S9.

It can be understood in the following video:

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