# what is 555 Timer? [closed]

what is timer 555 ??

how can we use this kind of timer ? how to create it ? any information will be useful ..

I have a friend who is interested in this topic , and I think that website is a suitable place to ask about this topic .

I hope that you can help.

• -1. Have you looked up 555 timer on Altavista? – Nick Alexeev Mar 11 '13 at 19:08
• @MrWhy: Wikipedia is your friend and it's usually trustworthy. – Gustavo Litovsky Mar 11 '13 at 19:18
• +1 to balance unfair -1s: I do not see anything wrong with asking here about the function of an electronic component. A search engine would return a link to this site if it is properly answered (so demanding an initial search engine search is either circular or like saying "why don't you first look at other sites, doesn't matter which"). Yes, Wikipedia is a fine source of information, and the page on the 555 timer is good. So? Are we not answering any electronics-related questions that are already answered in Wikipedia? What about other sites? – apalopohapa Mar 11 '13 at 19:53
• There is a two sided coin here. MrWhy, we are here to answer the question, not find you other pages that do, if you would like a general explanation of what a 555 timer is, it is a bit broad but a very very common question, I would be willing to make an exception for the google candy.. @others, we are trying to be the site google returns. Please consider this a warning for telling users to google something. It is rude and is the same as telling someone RTFM. If you consider a question below you then move to another question. – Kortuk Mar 11 '13 at 20:49
• @apolopaha - What is wrong with asking here first is that it is in effect asking other people to do trivial research that the poster could easily do themselves. That's basically impolite. The advantage of (more) static, non-interactive publishing over conversation is that most of the time only one person's effort is required. Conversational approaches such as this get saved for situations where the static resources are insufficient, or hard to find - neither of which is the case for the question as currently asked. – Chris Stratton Mar 11 '13 at 21:13

Many ages ago not long after the first caveman whittled a piece of silicon into a transistor, they learned how to make a bunch of transistors on the same hunk of silicon. This led to all kinds of things that we consider as always having been around, like the 741 opamp, 7805 regulator, and 2N2222 transistor. Yes, these things actually had beginnings. They didn't spring from the big bang fully formed as the myths tell us today.

Several groups of advanced cave men came up with lots of new and clever ways to whittle their silicon. A group calling themselves "National" brought forth the 741 opamp and the 7805 regulator, and the "Signetics" gang originated this 555 timer thing. It was pretty cool for its day. It is basically two comparators with fixed thresholds of 1/3 and 2/3 of the supply, and a flip-flop and some control circuitry to make other pins do things depending on what the comparators were seeing. You could wire up one of these things to self-oscillate, or produce a pulse of a certain width, delay a pulse, etc.

Eventually of course, we moved out of caves and got better and better at whittling silicon. Today we have many ways to do the things the ancient 555 timer did, but for less money, less board space, and a lot less power. The 555 timer deserves its recognition in the museum of neolithic inventions, but that is its place today. Some of the original cavemen are still around and still use 555 timers because that's what they are comfortable with, but those that have kept up with electronics since the ancient cave days leave the stone knives, bearskins, and 555 timers in the museum.

So today we appreciate the 555 timer for its place in the past, but it is not something for new designs except to honor history, for the few cavemen that are still with us, or for those that practise the ancient rituals for their own sake.

• The 555 was introduced by Signetics in 1972. Otherwise a fun read. – W5VO Mar 11 '13 at 21:45
• What non-555-ish alternative would you suggest for doing the things the 555 does without programming? I'll readily grant that the 7555 is better in many ways, but understanding that means understanding the 555. What other alternatives do you like? – supercat Mar 11 '13 at 21:49
• @supe: I wouldn't suggest doing it without programming, just like today we do wheels without using stone or wood. Rarely today do we need the function of a 555 timer by itself. Actually it was rare back then too, but generally accepted that individuals chips did that level of function. Today timing, frequency, and pulse generation gets done with clocks, timers, PWM modules and the like in a micro along with the other parts of the overall task. You just don't dedicate a whole chip to something like what a 555 timer did no more than a chip to perform 4 NAND functions or 6 inversions. – Olin Lathrop Mar 11 '13 at 22:13
• One thing 555 and some relatives (not the 741!) are still useful for is to learn newbies the art of electronics. Much like we don't use autopeds any more for any form of serious transport, but a kid often learns to use one well before learning a true bike. – Wouter van Ooijen Mar 12 '13 at 6:33
• I respectfully suggest that you understand this device well enough to have drawn an example circuit, described it in three sentences, and actually answered the question. That would be good content worthy of citation from Wikipedia. – Bob Stein Mar 25 '13 at 18:29

555 timers are used for timing.. i can save you the effort of typing and direct you to a good page with some examples to try out. doctronics 555 timer page

• thanx for this nice page:) – Fawzy Hegab Mar 11 '13 at 19:26
• your welcome, i found it useful learning about the 555 – rob j loranger Mar 11 '13 at 19:27
• Great :) , Good Luck . – Fawzy Hegab Mar 11 '13 at 19:31
• Link is currently broken. – gbarry Mar 22 '17 at 21:31