It is a 555 LED flashing circuit? Yep. How about a hex counter ... When [grandalf]’s friend showed them a project where a 555 timer was installed on an Arduino shield, they realized two things: ...

The 555 adjustable timer circuit starts timing when switched on. The green LED lights to show that timing is in progress. When the time period is over the green LED turns OFF, the red LED turns ON and ...

Take this Christmas tree for example, which uses a 555 timer and a CB4017 decade counter in order to drive some blinking LEDs. The ICs are through-hole, making the circuit fairly accessible to new ...