Simple eight-way digital display buzzer

Generally, the circuit of a buzzer is complicated and needs to be verified by auxiliary equipment such as simulators, application software, and computers. For beginners, it seems a bit beyond their ability. The circuit designed by the author is very simple. As long as you try it according to the diagram, you can assemble a simple eight-way buzzer.

The circuit principle is shown in the attached figure. It consists of IC1, a coding switch and a controller. The coding switch is composed of input terminals A, B, C, D in IC1, a diode and a button. To verify whether the coding switch is correct, just press any button. Make it have a positive level input, and the digital tube will display the corresponding number. The four coding lines A, B, C, and D are 1, 2, 4, and 8 respectively. 3 is obtained by inputting a positive level at the same time from 1+2, 5 is obtained from 1+4, 6 is obtained from 2+4, and 7 is obtained from 1+2+4. The diode plays a reverse cutoff role.

The controller is composed of thyristor and control terminal of IC1 (pins ⑦, ①, ②, and ⑥ of IC1). When any key is pressed, the thyristor will be triggered to conduct, so that the control terminal of IC1 always maintains a high-level input. Therefore, the pressed number is latched. In this way, the key pressed later will not work, and the digital tube will only display the key number pressed first.

The other end of the thyristor here is connected to the positive pole of the music piece. When the thyristor is turned on, the music piece is powered on and sounds. Thus, the whole answer function is completed. The music piece can be triggered when it is powered on, and it can also stop automatically, so there is no need to set a pause button.

When the reset button is pressed, the power supply of the thyristor is cut off and the control terminal of IC1 changes from high level to low level and is cleared, preparing for the next quick answer.