Dual color (4 line x 3 column) led, 12 white and 12 blue are intermittently switched controlled by two NPN transistors BC337. The speed and duty/cycle timing of lighting duration is determined by NE555 oscilator. The number of repetition of sequential lighting of each group of led is determined by 5-stage divide-by-10 Johnson counter with 10 decoded outputs and carry out bit (CD4017).
The intermittent lights from two group of led imitate the police car strobe lights.
The speed of switching off and on of led are continuously regulated by variable trimmer resistor.
24 LED Police Flasher - [Link]
The Hand Steadiness Tester is a game which tests the steadiness of your hand. The player has to take the ring from one end to another end without touching it to the wire. In this the player gets 4 turns. If the player touches the wire 4 times he has to reset the game & start the whole game from the beginning.
This project consists of IC 4017, a Buzzer, a Relay, some resistors, a Push button and 4 LEDs. There is also a PCB layout given. There are many types of Hand Steadiness Testers which are very simple. This New Hand Steadiness Tester is more advanced.
Hand Steadiness Tester – [Link]
The 555 Astable generates a clock for this circuit, an oscillator giving a square wave output at pin 3 which is counted by 4017 to give a running lights effect.
The decade counter-divider CD4017 has 10 outputs, for every low to high transition at the clock input, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on. You can vary the value of R2 100K Linear potentiometer to make LEDs run fast or slow.
Running Lights with CD4017 - [Link]
When you touch the TOUCH PLATE wires, the LEDs start flashing in a similar manner to a dice rolling over and over. This gradually slows down to rest and a number is displayed exactly like the spots on a dice.This circuits use LM555 and CD4017.It’s very fun. [via]
LED Dice - [Link]