Electronic Doorbell Circuit using a 555 timer and a CD4017 decade counter

Electronic Doorbell circuit that lets know that someone is at the door. Made with 555 timer and 4017 decade counter allowing to change the tone of each note

This Electronic two-way traffic light circuit achieves the functionality of a typical two-way traffic light using a 555 timer and a CD4017 decade counter.

LED Sequencer using 4017 Decade Counter (LED Chaser). This circuit has 10 LEDs connected to the decade counter outputs. LEDs light up in sequence. Only one LED is ON at a time

This circuit shows the familiar lights which are used on police cars. It uses a 555 timer as a clock for the 4017B decade counter, two transistors and twelve LEDs