555 Timer Flashing LED

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I found a 555 Timer IC from an old PCB and decided to play with it. Basically what a 555 Timer does is provide time delays by creating oscillations. Just imagine it like a function generator but only for square waves.

I don’t have much knowledge in the 555 Timer but from what I’ve read so far, it has 3 modes of operation. They are monostable, bistable, and astable. In this demo, I’ll be using the astable mode because it can provide a square wave oscillation at pin 3. With that, I can do a simple flashing LED circuit like I’ve done in the past with both PIC and the Arduino. Only this time there’s no microcontroller and programming involved.

In a microcontroller, we can program it to flash the LED in any desired intervals but for the 555 Timer, the intervals (or the oscillation frequency) is based on the resistor and capacitor values used in the circuit. Actually I’m still not familiar with how to calculate it, so I went to look for a schematic online.

This circuit uses a 1uF capacitor but unfortunately I don’t have it, so I played mix and match with all the resistors and capacitors I have to get a low enough frequency that the LED flashes can be seen by the eye.

Somehow I ended up using two 100uF capacitors in the circuit and I will report back why. In the meantime, here’s a video showing how the circuit works.

Thanks for reading ­čÖé

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