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555 timer chip

Discussion in 'Electronic Basics' started by Smokeyone, Dec 18, 2003.

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  1. Smokeyone

    Smokeyone Guest

    After searching various sites trying to find a timer circut for one
    second on & one second off I now find there are various types of 555
    chip eg....NE555 or NE555D SMD plus assorted others. Could anyone
    advise please.

    Thanks

    Smokeyone
     
  2. Steve

    Steve Guest

    I now find there are various types of 555 chip eg....NE555 or NE555D SMD
    Here's a start;

    DESCRIPTION TEMP RANGE ORDER CODE
    8­Pin Plastic Small Outline (SO) Package 0 to +70 °C NE555D
    8­Pin Plastic Dual In­Line Package (DIP) 0 to +70 °C NE555N
    8­Pin Plastic Small Outline (SO) Package -40 °C to +85 °C SA555D
    8­Pin Plastic Dual In­Line Package (DIP) -40 °C to +85 °C SA555N
    8­Pin Plastic Dual In­Line Package (DIP) -55 °C to +125 °C SE555CN
    8­Pin Plastic Dual In­Line Package (DIP) -55 °C to +125 °C SE555N


    Get the data sheets and READ THEM! All the info you need is out
    there, you've just gotta look for it.

    google "555 timer types" and get this among many others;
    http://www.uoguelph.ca/~antoon/gadgets/555/555.html
     
  3. Smokeyone

    Smokeyone Guest


    Thanks for the info & the site suggestion.

    Smokeyone


    to e-mail me, delete mail from address
     
  4. You might want to use the CMOS version for that low a rate.
    Check for 7555 (Intersil).


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    http://www.harvardrepeater.org
     
  5. Byron A Jeff

    Byron A Jeff Guest

    -After searching various sites trying to find a timer circut for one
    -second on & one second off I now find there are various types of 555
    -chip eg....NE555 or NE555D SMD plus assorted others. Could anyone
    -advise please.

    The 555 isn't going to be your best bet if you need anything close to precise
    timing because the timing will drift based on both tolerance of the RC
    components and the temperature. Also it isn't easy to get a 50 percent
    duty cycle with the 555.

    If this isn't battery powered, one of the most reliable source of time is
    the power cycle from the wall. A center tapped transformer, along with a
    single current limiting resistor and a zener diode, is all that's required
    to get near rock solid 60 Hz pulses that you can divide/count down to your
    heart's content. The transformer also will provide power to your project
    with a bridge rectifier, voltage regulator, and an additional couple of
    caps.

    I use the above setup to drive any precise/long term timing PIC projects I
    put together. Works like a champ.

    This howstuffworks.com page describes the exact setup I'm talking about:

    http://home.howstuffworks.com/digital-clock4.htm

    Of course I believe the rest of the circuit past the power supply/60 Hz
    generator falls down because it's a perfect application for a microcontroller.
    Using discrete TTL, while useful as a learning exercise, is impractical for
    real implementations. However if you're going discrete, pay attention to the
    divide by 6 and divide by 10 on the subsequent pages.

    Howstuffworks also talks about how to build a digital clock with a basic stamp.
    They point out that the setup will cost $100. Insane. Fortunately you can
    skip the stamp and program to an inexpensive bare microcontroller. Presuming
    you're only wanting the same 1 Hz output as the 555, a 16F628 can be had
    for less than $3, or on sample from Microchip.

    BAJ
     
  6. For a 2 second astable, which is what I understand the OP wants, I'd
    have thought a 555 was the obvious solution. Or half a 4001 or 4011.

    A suitable circuit I posted here 3 months ago for a similar
    requirement is shown at
    http://www.terrypin.dial.pipex.com/Images/555Astable2s.gif
     
  7. Byron A Jeff

    Byron A Jeff Guest

    As I pointed out above it depends on the precision. A 555 is fine for 2 Hz
    +/- 10 percent. But if it needs to be spot on, it'll fail miserably.
    Your own table points out that it isn't exactly 2 Hz. It'll be inaccurate
    from the start, and after you tune it, it'll drift.

    That's all I was pointing out.

    BAJ
     
  8. Smokeyone

    Smokeyone Guest

    Thanks everyone for the replies. It certaintly will give me enough
    research to go over Christmas.

    Smokeyone

    to e-mail me, delete mail from address
     
  9. Mighty

    Mighty Guest

    Your own table points out that it isn't exactly 2 Hz. It'll be
    inaccurate
    He doesn't want 2 Hz. He wants a period of 2 Seconds. That's 500mHz.

    Craig
     
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