The 555 timer is one of the most popular and versatile integrated circuits used by electronics hobbyists and engineers. With just a few external components, you can build tons of different circuits using the 555 timer. In this post, I will show you how to build a simple 555 timer circuit using less than $5 worth of parts. This simple circuit is something that most people don't know about, but it's an easy and fun electronics project for beginners.
An Introduction to the 555 Timer
The 555 timer chip is an 8-pin integrated circuit that can be configured as an astable multivibrator to generate pulses and square waves. Some key features of the 555 timer:
- Can operate from 4.5V to 15V power supply
- Available as TTL or CMOS versions
- Timing from microseconds to hours
- Output current up to 200mA
The 555 timer chip provides very stable timing even with a simple configuration. That's why it's so popular for timers, oscillators, and other wave generation circuits.
Parts Needed for Our 555 Timer Circuit
To build the 555 timer circuit described in this article, you will need the following parts:
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1 x 555 timer IC - The heart of the circuit. Choose the common NE555 version.
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2 x 0.1 uF capacitors - Ceramic disc capacitors.
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1 x 10K ohm resistor
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1 x 100K ohm potentiometer
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1 x LED - Pick any color LED.
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1 x 9V battery snap connector - To connect a 9V battery to the circuit.
All these basic components can be purchased for well under $5 total. In fact, you may already have some of these parts laying around!
Circuit Design and Operation
The schematic diagram for our 555 timer circuit is shown below:
This circuit uses the 555 timer in astable mode to generate a oscillating output waveform. The frequency of oscillation depends on the values chosen for R1, R2 and C1. Let's examine how it works:
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R1 and R2 form a voltage divider that controls the threshold and trigger pins. Together with C1, they determine the oscillation frequency.
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C1 charges and discharges between 1/3 and 2/3 of the supply voltage to generate the output waveform.
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Output pin 3 generates a square wave oscillating between 0V and VCC.
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The LED and series resistor connect to the output to visually indicate the oscillator operation.
With the components values shown, the circuit oscillates at around 2 Hz. This can be sped up or slowed down by changing the capacitor and resistor values.
Building the Circuit
Follow these steps to build the 555 timer circuit on a breadboard or perfboard:
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Insert the 555 timer chip into the breadboard. Be sure to orient it properly with the notch or dot aligned as per the datasheet.
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Connect pins 4 and 8 to VCC (positive supply) and pins 1 and 5 to ground.
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Insert a 10K resistor from pin 7 to VCC. This pulls the discharge pin high.
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Connect a 100K potentiometer between pins 6 and 7. The wiper goes to pin 6.
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Install a 0.1 uF capacitor between pins 6 and 2.
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Add another 0.1 uF capacitor between pins 1 and 2. This couples the threshold and trigger pins.
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Connect the LED and series resistor from pin 3 to ground.
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Connect your 9V battery to the VCC and ground rails to power the circuit.
Once everything is connected properly, you should see the LED flashing at a steady rate of about 2 Hz. Congratulations, you've built a working 555 timer circuit!
Applications and Uses
This simple 555 oscillator circuit has many practical uses:
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Timing/flashing LEDs - Create lighting effects, visual metronome etc.
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Pulse generator - Provide clock signal for digital logic circuits.
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Tone generator - Connect a speaker instead of LED to make audio tones.
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PWM control - Modify the circuit for PWM speed control, dimming LEDs etc.
With just a few additional components, the 555 can be configured into all kinds of cool timers, controllers and sequencers. It's a building block that every electronics hobbyist should learn to use proficiently.
So that's how you can build a simple and useful 555 timer circuit using less than $5 worth of common electronic components. This barebones oscillator is a great starting point for learning 555 timer basics. Let me know in the comments if you build this circuit and what you modify or add to it!