Campus lecturer random turntable case

The random digital circuit is made using 555 timer and CD4017B chip. In order to facilitate students to learn and use, some components are modified based on the Lichuang eda open source project to make a random turntable.

      The circuit consists of a pulse generator and a shift register. When the S switch is pressed, transistor Q1 is turned on, NE555 forms a multivibrator, and pin 3 outputs a pulse sequence that causes the Q0~Q9 pins of CD4017 to output high levels one after another. When S is disconnected, that is, when the button is released, due to the existence of the large capacitance of C1, the triode will not disconnect immediately, but will slowly turn off as the capacitor discharges. The phenomenon is that the rotation speed of the LED slowly slows down until a certain lamp is turned on. Stop at , realize the function of random turntable.

      In this circuit, you can change the time it takes for the LED to stop after releasing the button by changing the capacitance size of C1. The larger the capacitance value, the longer the waiting time. Changing the value of R1 can change the speed of LED flow. The larger the resistance, the slower the diode rotates.

     The case is very feasible and the students gained a lot.

Reference open source project link: https://oshwhub.com/LCEDA_Electronic-production/03-Digital_random_turntable