Circuit diagram analysis of electronic question and answer button table

This is the circuit diagram of the electronic quiz button table. The circuit is simple, easy to build and certainly not expensive. This quiz circuit is for four game participants. It determines the contestant who first presses the switch (S1 to S4) to answer the question and locks the remaining three entries, so the buttons of the other contestants will not work. At the same time, the corresponding audio alarm sounds and the bulb lights up. The quiz table can be used for a larger number of contestants by simply adding a buzzer, bulb, MOSFET and diode.

This electronic quiz circuit provides an option to vary the time that a single buzzer and corresponding light bulb should be "on" after a particular contestant presses a button. These timings can be set as required by presets VR1 to VR4.

This circuit operates from a 12V, 1.5A power supply. The current rating of the power supply should be based on the load (wattage of the bulb). For higher wattage bulbs, use a power supply with a higher current rating. LEDs can replace low current power supplies (batteries).

Here is a diagram of how to set up the electronic quiz buttons on the quiz station:

If participant A presses switch S1, MOSFETT1 is triggered, the corresponding bulb BL1 (connected between the drain of the MOSFET and the 12V power supply) lights up, and the piezo buzzer PZ1 connected in parallel with the bulb BL1 sounds for a preset time. At the same time, capacitor C1 is charged to 12V and then discharged through the preset VR1. The discharge time of capacitor C1 is determined by the preset VR1. For example, if the resistance of the preset VR1 is set to 4.7k, it will give a delay of about 4 seconds, which means that the buzzer PZ1 and the bulb BL1 will be "on" for 4 seconds. It also indicates that participant A is the first one to press his switch. Even if any other participant, say participant B, presses switch S2 after participant A has already pressed switch S1, the buzzer PZ2 and the bulb BL2 will not work because the gate voltage of MOSFETT2 is not triggered because it is grounded through R2 and D1. The same principle applies to other contestants.

You can also use a set of LEDs instead of the bulb to create a better decoration for the appearance of the lamp.