The 555 is a single-chip version of a commonly used circuit called a multivibrator, which is useful in a wide variety of electronic circuits. The 555 timer chipis probably the most popular integrated circuit ever made.

You can use the 555 chips for basic timing functions, such as turning a light on for a certain length of time, or you can use it to create a warning light that flashes on and off. You can use it to produce musical notes of a particular frequency, or you can use it to control positioning of a servo device.

Here is the arrangement of the eight pins in a standard 555 IC. The 555 comes in an 8-pin DIP package.





Here are the functions of each of the eight pins:

  • Ground: Pin 1 is connected to ground.
  • VCCPin 8 is connected to the positive supply voltage. This voltage must be at least 4.5 V and no greater than 15 V. It’s common to run 555 circuits using four AA or AAA batteries, providing 6 V, or a single 9 V battery.
  • Output: Pin 3 is the output pin. The output is either low, which is very close to 0 V, or high, which is close to the supply voltage that’s placed on pin 8. The exact shape of the output — that is, how long it’s high and how long it’s low, depends on the connections to the remaining five pins.
  • Trigger: Pin 2 is the trigger, which works like a starter’s pistol to start the 555 timer running. The trigger is an active low trigger, which means that the timer starts when voltage on pin 2 drops to below one-third of the supply voltage. When the 555 is triggered via pin 2, the output on pin 3 goes high.
  • Discharge: Pin 7 is called the discharge. This pin is used to discharge an external capacitor that works in conjunction with a resistor to control the timing interval. In most circuits, pin 7 is connected to the supply voltage through a resistor and to ground through a capacitor.
  • Threshold: Pin 6 is called the threshold. The purpose of this pin is to monitor the voltage across the capacitor that’s discharged by pin 7. When this voltage reaches two thirds of the supply voltage (Vcc), the timing cycle ends, and the output on pin 3 goes low.
  • Control: Pin 5 is the control pin. In most 555 circuits, this pin is simply connected to ground, usually through a small 0.01 μF capacitor. (The purpose of the capacitor is to level out any fluctuations in the supply voltage that might affect the operation of the timer.)
  • Reset: Pin 4 is the reset pin, which can be used to restart the 555’s timing operation. Like the trigger input, reset is an active low input. Thus, pin 4 must be connected to the supply voltage for the 555 timer to operate. If pin 4 is momentarily grounded, the 555 timer’s operation is interrupted and won’t start again until it’s triggered again via pin 2.

When used in a schematic diagram, the pins of a 555 timer chip are almost always shown in the arrangement depicted here. Supply voltage is at the top, ground is at the bottom, inputs are at the left, and outputs are at the right.









  1. I just want to say I am very new to weblog and certainly savored your web-site. Almost certainly I’m going to bookmark your blog post . You actually have perfect article content. Appreciate it for sharing with us your webpage.

  2. What a stuff of un-ambiguity and preserveness of precious know-how about unexpected feelings.

  3. I was highly pleased to acquire this web-site.I wanted to thanks for your time for this amazing read!! I surely enjoying each and every little bit of it and I have you bookmarked to take a look at new stuff you blog post.

  4. Only wanna say that this is extremely helpful, Thanks for taking your time to write this.

  5. Hey There. I found your blog using man. This is an extremely well written article. I will be sure to bookmark it and return to read more of your useful info. Thanks for the post. I’ll definitely comeback.

  6. This design is wicked! You obviously know how to keep a reader amused.
    Between your wit and your videos, I was almost moved to start my own blog (well, almost.
    ..HaHa!) Fantastic job. I really loved what you had to say, and more than that, how you presented
    it. Too cool!

  7. I’ve been absent for some time, but now I remember why I used to love this website. Thank you, I will try and check back more frequently. How frequently you update your site?

  8. I genuinely enjoy studying on this website , it has superb articles .

  9. I’ve be aware of a little nutrients here. Without doubt well importance bookmarking regarding revisiting. I shock immediately how a large amount effort a person situate to help bring in this classify of brilliant enlightening website.

  10. You made some decent points there. I regarded on the internet for the issue and found most people will associate with with your website.

  11. Very nice post. I not too long ago discovered your weblog as well as wished to point out that I’ve genuinely cherished looking the blog web-site articles. All points viewed as I’ll be subscribing to the feed and I we do hope you make once again promptly!

  12. I have been exploring for a little bit for any high-quality articles or weblog posts in this sort of area . Exploring in Yahoo I ultimately stumbled upon this website. Reading this info So iˇm glad to convey that I’ve an incredibly excellent uncanny feeling I discovered just what I needed. I most indisputably will make certain to donˇt fail to remember this website and give it a look regularly.

  13. I’m just commenting to make you understand of the remarkable discovery my friend’s daughter had studying your site. She figured out a wide variety of details, including what it is like to possess an amazing coaching mindset to have most people easily know chosen very confusing subject areas. You really exceeded her expected results. Many thanks for providing the priceless, safe, educational and unique tips about your topic to Julie.

  14. Youre so cool! I dont suppose Ive read anything similar to this prior to. So great to uncover somebody with some original thoughts on this subject. realy appreciation for beginning this up. this internet website is one particular location that is required on the internet, somebody if we do originality. useful job for bringing new stuff for the internet!

  15. Glad to become one of numerous guests on this wonderful web site : D.

  16. Simply wish to say your article is as astonishing. The clearness in your post is just nice and i could assume you are an expert on this subject. Well with your permission let me to grab your feed to keep up to date with forthcoming post. Thanks a million and please carry on the enjoyable work.

  17. excellent publish, very informative. I ponder why the opposite experts of this sector don’t notice this. You should continue your writing. I am confident, you’ve a huge readers’ base already!

  18. Hey pretty cool website!! Man .. Beautiful .. Amazing .. I will bookmark your internet site and take the feeds also…I’m happy to discover lots of handy info here inside the post, we need to have develop a lot more strategies in this regard, thanks for sharing. . . . . .

  19. This is very interesting, You are a very skilled blogger.

    I have joined your feed and look forward to seeking more of your excellent post.

    Also, I have shared your website in my social networks!

    • Thanks for the support friend, thanks for following my blog and sharing it with friends, I will surely not disappoint you and all the followers of this blog, I will give it my best with the time i have

Leave a Reply

Your email address will not be published.



Theme by Anders NorenUp ↑