As Christmas is coming I thought of making a costume PCB badge snow man. What it is for is as it is small we can attach it to our keys as a key chain and which looks op.

What it basically does it that the snow man has 2 LED's as eyes which blink alternatively when the switch is turned on with a delay. It is made with the help 555 timer which is heart of the circuit.

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, delay, pulse generation, and oscillator applications. Derivatives provide two (556) or four (558) timing circuits in one package. It was commercialized in 1972 by Signetics. Numerous companies have made the original bipolar timers and similar low-power CMOS timers too. In 2017, it was said over a billion 555 timers are produced annually by some estimates, and "probably the most popular integrated circuit ever made.". Here I have used NE555 model for the circuit.

The 555 timer is a chip that can be used to create pulses of various durations, to output a continuous pulse waveform of adjustable pulse width and frequency, and to toggle between high and low states in response to inputs. 

555 timer pin out

Here I made the circuit to work in a Bi Flasher Mode. This means at the output Pin, two LEDs are connected in such a way that when a positive signal gets out of Pin 3 this will make LED 2 Glow and LED 1 will remain LOW, and when the positive signals don't get out of Pin 3 LED 2 will become LOW and LED1 will start glowing.

To know more about the 555 timer working check this: link

Bi Flasher constantly turns Both LEDs ON and OFF by repetitive biasing of both LEDs through pin 3.

The flashing rate can be controlled by changing the value of the capacitor connected between Pin 2 and GND. I'm using a 10uf 16V capacitor.

We can calculate the ON time with the help of the simple formulae

So 555 IC automatically fall back to the stable state (LOW) after the time determined by the RC network. This duration of quasi stable state can be calculated using this 555 Monostable Calculator or can be calculated with the formulae given below: T= 1.1*R1*C1 Seconds where R1 is in OHM and C1 is in Farads

Circuit Diagram

Replicate this project simply

1) Making the connections as shown in the circuit diagram.

2) Check the circuit with the TinkerCAD or any other simulation software.

3) Try to make the same circuit on the bread board.

4) If everything works fine download the Gerber files and order the PCB.

Output