Many electronics circuits and projects for learning in simple ways.

555 Pulse Generator circuit

This is a pulse generator circuits or standard Astable Multivibrator oscillator or free running circuit using IC555 timer,NE555,LM555 . We use it for digital Logic circuits. IC-555 is popular easy to use small size with 8 pins. It is combining  analog and digital chip. Basic using it need the voltage supply 5V to 15V, Maximum supply voltage 16v – 18v, Current consumption  about 10mA, Maximum Output Current is 200mA. Maximum  frequency  output is 500kHz.

There are many ways to use the IC555.  We can use  them in three different types of oscillators:
(1)Astable Multivibrator oscillator
If frequencies  more than 1 cycle per second, it is an oscillator (pulse generator or square wave oscillator).
But frequencies lower than 1 cycle per second it is TIME DELAY.
(2) Monostable (ONE SHOT) changes state only once per trigger pulse
(3) Voltage Controlled Oscillator (VCO)

Now we will learn about pulse generator with IC-555 below basic circuit.

Simple Pulse Generator circuit by IC-555

simple pulse generator circuit using IC-555

In the circuit above. First of all the current from the power supply flow to the capacitor-C1 charges via the Resistor-R1 and R2, then the voltage in the capacitor reaches 2/3 of the supply voltage, pin 6 detects  this voltage, cause pin 7 cut off this voltage to Ground(0v).
Thus the capacitor-C1 discharges through the resistor-R2 until its voltage is 1/3 of the supply and pin 2 detects this voltage and pin 7 not connect (turns off).  The C1 will charge and voltage across it grow up  again to repeat the cycle.

The top resistor prevent pin 7  may damage as it shorts to 0v when pin 6 detects 2/3 supply voltage.
Its resistance is smaller than R2 and does not come into the timing of the oscillator.

The output frequency will be approximately 1kHz and the duty cycle 50-50,
The Frequency output (F) = 1/{(R1+2R2)*C1}.

The values units in the formula in ohms, farads, seconds and hertz. This formula is much simpler than that of the previous circuit.

Suppose R1 = 1k, R2 = 10k and C = 0.1uF  The result is approx 900Hz

Parts you will need
R1___________100K 1/4W Resistors tolerance: 5%
VR1__________1M Potmeter
C1,C2________0.01uF 50V Ceramic Capacitors
IC1__________NE555 Timer

We use simple 555 pulse generator idea to builds many circuits for example below

High Power Pulse Generator using LM350T and NE555


Pulse Generator by IC LM350T and 555

The danger beep circuit using IC-555
The danger beep circuit using IC-555

Tone Burst Generator using LM555

Tone Burst Generator using LM555

Annoying high pitch noise generator using IC-555

Annoying high pitch noise generator using IC-555

  1. Audio generator is controlled by light
  2. Tapping morse code circuit
  3. 555 timer audio alarm circuits

This Post Has 33 Comments

  1. very nice & good service i hope people will happy with service

  2. I need a 555 circuit that must be triggered on by a switch and stay on for about 20 seconds.
    Will you email me a diagram how to do that?

  3. I need a sch. of an astable 555 with an on time of .75sec., a dwn time of 5sec, or there abouts. All I need is values of r1, r2 and c1. Can you help me?
    I would greatly appreciate it.
    Bob W.

  4. special thanks!
    very very nice sit!

  5. i need clock pulse for counter circuit for increment by one counter ic 74hc393 so please tell me how can i do……

  6. I want a pulse generator. That must be get more output pulse .Please help me.

  7. I need a 555 circuit that must be triggered on by a switch and stay on for about 20 seconds.
    Will you email me a diagram how to do that?

  8. Your site and projects are awesome.You are teaching me electronics the no one could.
    Thanks
    Paul Perold
    Cape town
    South Africa

  9. which is R1?

  10. Hi,
    I am sorry for late answer you.

    R1 = VR1

    This is simple circuit.

  11. each time i used to read smaller posts that as well clear their motive, and that is also
    happening with this post which I am reading at this time.

  12. I want a pulse generator for time period of about 0.5sec please mail me the circuit. And further details of it

  13. i want to replace ic mm 5369 with ic 555 in my digital clock using mm 5387 clock chip.please give me a circuit for this purpose.Presently it runs on 12v dc.the ic mm 5369 is not available so please help me.

  14. hi what values should I use to make a 8hz oscillator somewhere near schumann resonance?

  15. some componet failure any iam don’t identify

    2 qustin
    1. duplicate component
    2. Circuit wrong connected

  16. Hi Solo
    Thanks for your feedback.
    This circuit is correct.

  17. What cap did you used? Ceramic or mylar? Thanks btw

  18. Hi Masterlogic,
    Thanks for your feedback.
    You can use both ceramic and mylar capacitor. or MKP or MKT that good capacitor which is expensive type.

  19. momename, can you create a variable frequency clock pulse that varies from 1Hz to 60Hz. Can you send it to my email? I badly need it. Thanks and more power. 😀

  20. Thank you man! I really appreciate it. More power 🙂

  21. Looking for a simple pulse generator to build or buy for experimental work.please advise on who can assist, Regards

  22. If the circuit is implemented without using 555 timer ic; then we need to use comparators, SR latch and transistor. So how would the two circuits differ if SR latch is implemented using NAND gates or NOR gates?

  23. hi,
    I would like to know explanation about this circuit.

  24. what is the maximum range of frequency can we generate using this circuit?
    Is it possible to generate 4.3MHZ?

  25. i have 2 firing circuit for mosfet which is generated by ic 555,how i can obtained ac output from this

  26. There is a huge fault in this circuit. don’t post circuit that you have not built.

  27. Is it possible to place a potentiometer instead of the resistor to make a variable frequency? How would one go about varying the power in this circuit?

  28. Hi there,I log on to your new stuff named “Simple Pulse Generator circuit by IC 555 Timer” like every week.Your writing style is awesome, keep up the good work! And you can look our website about proxy list.

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