555 timer numbers?

Discussion in 'General Electronics Chat' started by Lightfire, May 19, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Hello,

    I am confusing about 555 (NE555). In schematic dagram it have numbers but I am thinking if it is have also in real life.

    So, please look at my attachment (the big circled red). The timer has 1,2,3,4,5,6 numbers.

    Thanks
    help?
    thanks
     
  2. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    I figured Bill is probably at work so here is a 555 pic. The notch indicates the top, and the pins are numbered 1 - 8 starting at the top left, going down the left side, crossing the bottom and ending at the top right at pin 8 (counter-clockwise. )
     
  3. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    But as you may see there, there's only 6 numbers.:(Help? pls. :D

    Catapult
     
  4. orbiter

    Active Member

    Jun 17, 2010
    58
    3
    The pin numbers on the 555 go around the chip in an anti-clockwise direction, starting from the notch/dot in the chips upper surface. Any missing numbers just means they're unused in that particular circuit.

    Like this..

    http://en.wikipedia.org/wiki/File:555_Pinout.svg
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Not all schematics are really good. Go to the link and get a data sheet for a 555 timer - http://www.datasheetcatalog.com/datasheets_pdf/L/M/5/5/LM555CN.shtml

    You will see the schematic does not have the .01 uF cap on pin 5 (may not be needed in this circuit). Pin 7 is used in timing the output pulse, as is pin 6. The 555's are not supposed to be in astable configuration, so all they do is switch from on to off.

    What do you expect this circuit to do?
     
  6. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    As you may the bold line. Isn't it the one which will make the timer have 8 pins??? :(
     
  7. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
  8. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Hi, Catapult! :)

    As mentioned earlier, in this schematic, only the used pins are labeled. You may find some that have them all labeled. It doesn't really matter--The only pins numbers you really need to know are the ones you use. Make sense?

    The 555 timer already has 8 pins. The DIP (dual in-line package) is simply a socket for the chip. These can be helpful on permanent circuit boards, as it allows you to remove the chip (you don't have to solder the chip to the board--you only need to solder the socket).
    Der Strom
     
  9. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    Hey Catapult!

    On the schematic, it says pins 5 and 7 aren't used. ( pretty small writing, easy to miss. )

    @ everyone I'm not understanding how setting the "trigger line" high prevents other output led's from displaying, The 1n4148's prevent pin three from bias by the trigger line. Am I missing something here?
     
  10. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    Never mind... I see it now..... DUH.......

    looking at wrong end of horse:D
     
  11. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Got a special request via PM, so at the risk of repeating what every one has already said...

    The basics.

    This is a 8 pin chip top view...

    [​IMG]

    Pin 1 is the upper top left corner. It will either have a notch in the side or a dimple in the plastic as shown. The numbers go down and in a circle, so pin 8 is the top right corner. I'm including my pinout sheet which is part of my PaintCAD package, which labels each pin by number.

    If a pin number is not shown, it is not used. It really is that simple.

    If you want to see how a schematic matches against a real schematic you can look at any of my 555 articles. The first link is free. :D

    555 Schmitt Trigger


    So, get anything in the mail yet?
     
  12. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Um, just a couple of questions.

    1) If there is no label there, so the numberings at the schamtic really doesn't matter or what?

    2) Anyway, will the project will work then? :D
     
  13. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    As Been there said... What do you think it will do? Can you explain how you think it works? Understanding how it is supposed to work is important to electronics. The numbers show you how to connect the components.
     
  14. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    The labels (numbers) are only for the pins that are used. If you see a "2" on the schematic, it means that that is pin 2 of the 555 timer. The numbers on the schematic are crucial--without them, you wouldn't know which pin is which, and where each one connects.
    Der Strom
     
  15. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The stripboard layout clearly shows all 8 pins of each IC. It shows that pin 5 and pin 7 do not connect to anything.
     
  16. engrdm

    New Member

    Feb 19, 2010
    10
    0
    remember that schematic symbols are made in such a way that it is easy and neat to connect them . hence u will find alot of ICs that dont show the power and gnd pins. some reorder the pins to make the connections easy.. The chip in real life would be as is shown in datasheet. for 555 pin configuration check this link where the same issue is discussed
     
  17. radiohead

    Active Member

    May 28, 2009
    474
    31
    That schematic simply means pins 5 and 7 are not used. It says so on your schematic.
     
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