In this blog post, we will introduce the 555 Timer Integrated Circuit (IC). You’ll explore what it is, the three different modes and its pinout.
555 Timer (EN555)
The 555 timer is an integrated circuit, it is extremely versatile and can be used to build lots of different circuits.
The EN555 is usually used to generate continuous series of pulses. These series of pulses allow you to continuously blink an LED, for example.
The 555 timer can operate in three different modes:
- Monostable mode: usually used to create time delays
- Astable mode: outputs an oscillating pulse signal
- Bistable mode: the 555 timer changes its output depending on the state of two inputs
In this post, you’ll see an example in astable mode.
If you search on Google 555 timer datasheet, one of the first results should be a PDF datasheet.
This is a document with a lot of information, but what you really need to pay attention right now is to the pinout. Here’s the EN555 pinout:
This IC has 8 pins:
- Control Voltage
In a circuit diagram, usually the 555 timer is drawn as follows:
Pin 3 is the output. This pin generates an oscillation. The voltage is high, then low, then high, then low again and so on (this is called astable mode).
To make the 555 timer work in astable mode, you should wire your circuit like this:
The frequency of the oscillation can be adjusted by changing the values of the resistors R1 and R2 and the capacitance of the capacitor C.
The frequency can be calculated using the following expression:
With the output voltage that comes from pin 3, you can control anything you want (like an LED, speaker, motor, etc.).
Flashing an LED with the 555 Timer
In this section, you will flash an LED using the 555 timer in astable mode. So, we just need to add an LED to the output of the previous circuit.
These are the components you’ll need:
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- 9V battery
- Battery clip
- Red LED
- 2× 1kΩ resistor
- 470kΩ resistor
- 0.01uF capacitor (non-polarized)
- 1uF capacitor (electrolytic)
- Jumper wires
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This is the circuit diagram:
Wiring the circuit
You can either follow the previous schematic or follow the breadboard wiring diagram below. Finally, power up your circuit by connecting the battery to your breadboard:
In the end, you should see your LED blinking like this:
Note: replace your 1uF electrolytic capacitor with another capacitor that has a lower capacitance and see the LED flashing at a different rate. With lower capacitance values, the flash rate increases.
I hope you’ve learn something new today and you’ve found this explanation useful.
If you’d like to know more about electronics basics or if you’d like to start into the world of electronics make sure you check out our Electronics for Beginners eBook.
Thanks for reading!